115 |
115 |
116 \normalsize |
116 \normalsize |
117 \begin{center} |
117 \begin{center} |
118 \begin{tabular}{ll} |
118 \begin{tabular}{ll} |
119 Email: & christian.urban at kcl.ac.uk\\ |
119 Email: & christian.urban at kcl.ac.uk\\ |
120 Of$\!$fice: & S1.27 (1st floor Strand Building)\\ |
120 Office: & S1.27 (1st floor Strand Building)\\ |
121 Slides: & KEATS (also homework is there)\\ |
121 Slides: & KEATS (also homework is there)\\ |
122 \end{tabular} |
122 \end{tabular} |
123 \end{center} |
123 \end{center} |
124 |
124 |
125 |
125 |
126 \end{frame}} |
126 \end{frame}} |
127 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
127 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
128 |
128 |
129 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
129 |
130 \mode<presentation>{ |
130 |
131 \begin{frame}[c] |
131 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
132 \frametitle{Last Week} |
132 \mode<presentation>{ |
133 |
133 \begin{frame}[c] |
134 Andrew Secure RPC Protocol: |
134 \frametitle{Man-in-the-Middle} |
135 \bl{$A$} and \bl{$B$} share a key private \bl{$K_{AB}$} and want to identify |
135 |
136 each other\bigskip |
136 |
137 |
137 \end{frame}} |
138 \begin{itemize} |
138 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
139 \item \bl{$A \,\text{sends}\, B : A, N_A$} |
139 |
140 \item \bl{$B\,\text{sends}\, A : \{N_A, K'_{AB}\}_{K_{AB}}$} |
140 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
141 \item \bl{$A \,\text{sends}\, B : \{N_A\}_{K'_{AB}}$} |
141 \mode<presentation>{ |
142 \end{itemize} |
142 \begin{frame}[c] |
143 |
143 \frametitle{Facebook Privacy} |
144 \end{frame}} |
144 |
145 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
145 |
146 |
146 \end{frame}} |
147 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
147 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
148 \mode<presentation>{ |
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149 \begin{frame}[t] |
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150 \frametitle{Protocols} |
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151 |
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152 \mbox{} |
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153 |
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154 \begin{tabular}{l} |
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155 {\Large \bl{$A\;\text{sends}\; B : \ldots$}}\\ |
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156 \onslide<2->{\Large \bl{$B\;\text{sends}\; A : \ldots$}}\\ |
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157 \onslide<2->{\Large \;\;\;\;\;\bl{$:$}}\bigskip |
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158 \end{tabular} |
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159 |
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160 \begin{itemize} |
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161 \item by convention \bl{$A$}, \bl{$B$} are named principals \bl{Alice\ldots}\\ |
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162 but most likely they are programs, which just follow some instructions (they are more like roles)\bigskip |
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163 \item<2-> indicates one ``protocol run'', or session, which specifies some |
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164 order in the communication |
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165 \item<2-> there can be several sessions in parallel (think of wifi routers) |
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166 \end{itemize} |
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167 |
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168 \end{frame}} |
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169 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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170 |
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171 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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172 \mode<presentation>{ |
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173 \begin{frame}[c] |
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174 \frametitle{Last Week} |
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175 |
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176 |
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177 \bl{$A$} and \bl{$B$} share the key \bl{$K_{AB}$} and want to identify |
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178 each other\bigskip |
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179 |
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180 \begin{itemize} |
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181 \item \bl{$A \,\text{sends}\, B : A, N_A$} |
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182 \item \bl{$B\,\text{sends}\, A : \{N_A, K'_{AB}\}_{K_{AB}}$} |
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183 \item \bl{$A \,\text{sends}\, B : \{N_A\}_{K'_{AB}}$} |
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184 \end{itemize} |
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185 \end{frame}} |
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186 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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187 |
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188 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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189 \mode<presentation>{ |
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190 \begin{frame}[c] |
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191 \frametitle{Defeating Challenge-Response} |
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192 |
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193 \noindent |
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194 A \alert{reflection attack}: an intruder \bl{$I$} impersonates \bl{$B$}. |
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195 |
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196 \begin{center} |
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197 \begin{tabular}{@{\hspace{-7mm}}c@{\hspace{1mm}}c@{}} |
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198 \begin{tabular}{@{}l@{}} |
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199 \onslide<1->{\bl{$A \,\text{sends}\, I : A, N_A$}}\\ |
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200 \onslide<4->{\bl{$I \,\text{sends}\, A : \{N_A,\!K'_{\!AB}\}_{K_{\!AB}}$}}\\ |
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201 \onslide<5->{\bl{$A \,\text{sends}\, I : \{N_A\}_{K'_{AB}}$}}\\ |
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202 \end{tabular} |
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203 & |
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204 \begin{tabular}{@{}l@{}} |
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205 \onslide<2->{\bl{$I \,\text{sends}\, A : B, N_A$}}\\ |
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206 \onslide<3->{\bl{$A \,\text{sends}\, I : \{N_A,\!K'_{\!AB}\}_{K_{\!AB}}$}}\\ |
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207 \onslide<6->{\bl{$I \,\text{sends}\, A : \{N_A\}_{K'_{AB}}$}}\\ |
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208 \end{tabular} |
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209 \end{tabular} |
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210 \end{center}\bigskip |
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211 |
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212 \onslide<7->{Sounds stupid: ``\ldots answering a question with a counter question''\medskip\\ |
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213 was originally developed at CMU for terminals to connect to |
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214 workstations (e.g., file servers)} |
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215 |
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216 \end{frame}} |
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217 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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218 |
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219 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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220 \mode<presentation>{ |
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221 \begin{frame}[c] |
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222 \frametitle{Identify Friend or Foe} |
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223 |
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224 \begin{center} |
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225 \onslide<3->{\mbox{}\hspace{3.4cm}\includegraphics[scale=0.55]{pics/MigInMiddle.jpg}} |
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226 \end{center} |
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227 |
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228 \begin{textblock}{6}(0.3,2) |
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229 \onslide<2->{ |
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230 198?: war between Angola (supported by Cuba) |
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231 and Namibia (supported by SA)} |
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232 \end{textblock} |
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233 |
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234 \begin{textblock}{3}(12.5,4.6) |
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235 \onslide<3->{ |
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236 \begin{tikzpicture} |
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237 \node at (0,0) [single arrow, fill=red,text=white, rotate=-50, shape border rotate=180]{``bystander''}; |
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238 \end{tikzpicture}} |
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239 \end{textblock} |
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240 |
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241 \begin{textblock}{3}(10.9,10) |
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242 \onslide<3->{ |
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243 \begin{tikzpicture} |
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244 \node at (0,0) [single arrow, fill=red,text=white, rotate=-40, shape border rotate=180]{attacker}; |
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245 \end{tikzpicture}} |
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246 \end{textblock} |
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247 |
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248 \only<4->{ |
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249 \begin{textblock}{6}(0.3,9) |
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250 being outsmarted by Angola/Cuba |
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251 ended SA involvement (?) |
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252 \end{textblock}} |
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253 \only<5->{ |
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254 \begin{textblock}{6}(0.3,13) |
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255 IFF opened up a nice side-channel attack |
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256 \end{textblock}} |
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257 \end{frame}} |
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258 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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259 |
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260 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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261 \mode<presentation>{ |
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262 \begin{frame}[c] |
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263 \frametitle{Encryption to the Rescue?} |
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264 |
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265 |
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266 \begin{itemize} |
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267 \item \bl{$A \,\text{sends}\, B : \{A, N_A\}_{K_{AB}}$}\hspace{1cm} encrypted\bigskip |
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268 \item \bl{$B\,\text{sends}\, A : \{N_A, K'_{AB}\}_{K_{AB}}$}\bigskip |
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269 \item \bl{$A \,\text{sends}\, B : \{N_A\}_{K'_{AB}}$}\bigskip |
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270 \end{itemize}\pause |
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271 |
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272 means you need to send separate ``Hello'' signals (bad), or worse |
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273 share a single key between many entities |
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274 \end{frame}} |
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275 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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276 |
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277 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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278 \mode<presentation>{ |
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279 \begin{frame}[c] |
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280 \frametitle{Protocol Attacks} |
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281 |
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282 \begin{itemize} |
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283 \item replay attacks |
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284 \item reflection attacks |
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285 \item man-in-the-middle attacks |
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286 \item timing attacks |
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287 \item parallel session attacks |
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288 \item binding attacks (public key protocols) |
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289 \item changing environment / changing assumptions\bigskip |
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290 |
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291 \item (social engineering attacks) |
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292 \end{itemize} |
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293 \end{frame}} |
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294 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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295 |
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296 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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297 \mode<presentation>{ |
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298 \begin{frame}[c] |
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299 \frametitle{Replay Attacks} |
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300 |
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301 Schroeder-Needham protocol: exchange of a symmetric key with a trusted 3rd-party \bl{$S$}: |
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302 |
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303 \begin{center} |
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304 \begin{tabular}{r@ {\hspace{1mm}}l} |
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305 \bl{$A \rightarrow S :$} & \bl{$A, B, N_A$}\\ |
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306 \bl{$S \rightarrow A :$} & \bl{$\{N_A, B, K_{AB},\{K_{AB}, A\}_{K_{BS}} \}_{K_{AS}}$}\\ |
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307 \bl{$A \rightarrow B :$} & \bl{$\{K_{AB}, A\}_{K_{BS}} $}\\ |
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308 \bl{$B \rightarrow A :$} & \bl{$\{N_B\}_{K_{AB}}$}\\ |
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309 \bl{$A \rightarrow B :$} & \bl{$\{N_B-1\}_{K_{AB}}$}\\ |
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310 \end{tabular} |
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311 \end{center}\bigskip\pause |
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312 |
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313 at the end of the protocol both \bl{$A$} and \bl{$B$} should be in the possession of the secret key |
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314 \bl{$K_{AB}$} and know that the other principal has the key |
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315 |
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316 \end{frame}} |
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317 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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318 |
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319 |
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320 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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321 \mode<presentation>{ |
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322 \begin{frame}[c] |
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323 \frametitle{Nonces} |
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324 |
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325 \begin{enumerate} |
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326 \item I generate a nonce (random number) and send it to you encrypted with a key we share |
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327 \item you increase it by one, encrypt it under a key I know and send |
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328 it back to me |
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329 \end{enumerate} |
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330 |
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331 |
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332 I can infer: |
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333 |
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334 \begin{itemize} |
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335 \item you must have received my message |
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336 \item you could only have generated your answer after I send you my initial |
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337 message |
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338 \item if only you and me know the key, the message must have come from you |
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339 \end{itemize} |
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340 |
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341 \end{frame}} |
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342 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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343 |
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344 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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345 \mode<presentation>{ |
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346 \begin{frame}[c] |
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347 |
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348 \begin{center} |
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349 \begin{tabular}{l} |
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350 \bl{$A \rightarrow S :$} \bl{$A, B, N_A$}\\ |
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351 \bl{$S \rightarrow A :$} \bl{$\{N_A, B, K_{AB},\{K_{AB}, A\}_{K_{BS}} \}_{K_{AS}}$}\\ |
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352 \bl{$A \rightarrow B :$} \bl{$\{K_{AB}, A\}_{K_{BS}} $}\\ |
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353 \bl{$B \rightarrow A :$} \bl{$\{N_B\}_{K_{AB}}$}\\ |
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354 \bl{$A \rightarrow B :$} \bl{$\{N_B-1\}_{K_{AB}}$}\pause\\ |
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355 \hspace{5cm}compromise \bl{$K_{AB}$}\pause\\ |
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356 \bl{$A \rightarrow S :$} \bl{$A, B, N'_A$}\\ |
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357 \bl{$S \rightarrow A :$} \bl{$\{N'_A, B, K'_{AB},\{K'_{AB}, A\}_{K_{BS}} \}_{K_{AS}}$}\pause\\ |
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358 \bl{$I(A) \rightarrow B :$} \bl{$\{K_{AB}, A\}_{K_{BS}} $}\hspace{0.5cm} replay of older run\pause\\ |
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359 \bl{$B \rightarrow I(A) :$} \bl{$\{N'_B\}_{K_{AB}}$}\\ |
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360 \bl{$I(A) \rightarrow B :$} \bl{$\{N'_B-1\}_{K_{AB}}$}\ |
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361 \end{tabular} |
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362 \end{center}\pause |
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363 |
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364 \bl{$B$} believes it is following the correct protocol, |
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365 intruder \bl{$I$} can form the correct response because it knows \bl{$K_{AB}$} and |
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366 talks to \bl{$B$} masquerading as \bl{$A$} |
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367 \end{frame}} |
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368 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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369 |
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370 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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371 \mode<presentation>{ |
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372 \begin{frame}[c] |
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373 |
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374 \begin{center} |
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375 \includegraphics[scale=0.5]{pics/dogs.jpg} |
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376 \end{center} |
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377 |
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378 \end{frame}} |
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379 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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380 |
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381 |
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382 |
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383 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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384 \mode<presentation>{ |
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385 \begin{frame}[c] |
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386 \frametitle{Replay Attacks} |
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387 |
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388 Andrew Secure RPC protocol: exchanging a new key |
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389 between \bl{$A$} and \bl{$B$} |
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390 |
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391 \begin{center} |
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392 \begin{tabular}{l} |
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393 \bl{$A \rightarrow B :$} \bl{$A, \{N_A\}_{K_{AB}}$}\\ |
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394 \bl{$B \rightarrow A :$} \bl{$\{N_A+1, N_B\}_{K_{AB}}$}\\ |
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395 \bl{$A \rightarrow B :$} \bl{$\{N_B+1\}_{K_{AB}}$}\\ |
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396 \bl{$B \rightarrow A :$} \bl{$\{K^{new}_{AB}, N^{new}_B\}_{K_{AB}}$}\\ |
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397 \end{tabular} |
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398 \end{center}\bigskip\pause |
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399 |
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400 Assume nonces are represented as bit-sequences of the same length as keys |
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401 \begin{center} |
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402 \begin{tabular}{@{}l@{}} |
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403 \bl{$A \rightarrow B :$} \bl{$A, \{N_A\}_{K_{AB}}$}\\ |
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404 \bl{$B \rightarrow A :$} \bl{$\{N_A+1, N_B\}_{K_{AB}}$}\\ |
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405 \bl{$A \rightarrow I(B) :$} \bl{$\{N_B+1\}_{K_{AB}}$}\hspace{0.5mm}intercepts\\ |
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406 \bl{$I(B) \rightarrow A :$} \bl{$\{N_A+1, N_B\}_{K_{AB}}$}\hspace{0.5mm}resend 2nd msg\\ |
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407 \end{tabular} |
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408 \end{center} |
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409 \end{frame}} |
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410 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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411 |
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412 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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413 \mode<presentation>{ |
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414 \begin{frame}[c] |
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415 \frametitle{Time-Stamps} |
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416 |
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417 The Schroeder-Needham protocol can be fixed by including a time-stamp (e.g., in Kerberos): |
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418 |
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419 \begin{center} |
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420 \begin{tabular}{r@ {\hspace{1mm}}l} |
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421 \bl{$A \rightarrow S :$} & \bl{$A, B, N_A$}\\ |
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422 \bl{$S \rightarrow A :$} & \bl{$\{N_A, B, K_{AB},\{K_{AB}, A, T_S\}_{K_{BS}} \}_{K_{AS}}$}\\ |
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423 \bl{$A \rightarrow B :$} & \bl{$\{K_{AB}, A, T_S\}_{K_{BS}} $}\\ |
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424 \bl{$B \rightarrow A :$} & \bl{$\{N_B\}_{K_{AB}}$}\\ |
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425 \bl{$A \rightarrow B :$} & \bl{$\{N_B-1\}_{K_{AB}}$}\\ |
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426 \end{tabular} |
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427 \end{center}\bigskip\pause |
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428 |
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429 but nothing is for free: then you need to synchronise time and possibly become a victim to |
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430 timing attacks |
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431 |
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432 \end{frame}} |
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433 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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434 |
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435 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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436 \mode<presentation>{ |
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437 \begin{frame}[c] |
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438 |
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439 It can also be fixed by including another nonce: |
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440 |
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441 \begin{center} |
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442 \begin{tabular}{r@ {\hspace{1mm}}l} |
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443 \bl{$A \rightarrow B :$} & \bl{$A$}\\ |
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444 \bl{$B \rightarrow A :$} & \bl{$\{A, N_B\}_{K_{BS}}$}\\ |
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445 \bl{$A \rightarrow S :$} & \bl{$A, B, N_A, \{A, N_B\}_{K_{BS}}$}\\ |
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446 \bl{$S \rightarrow A :$} & \bl{$\{N_A, B, K_{AB},\{K_{AB}, A, N_B\}_{K_{BS}} \}_{K_{AS}}$}\\ |
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447 \bl{$A \rightarrow B :$} & \bl{$\{K_{AB}, A, N_B\}_{K_{BS}} $}\\ |
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448 \bl{$B \rightarrow A :$} & \bl{$\{N_B\}_{K_{AB}}$}\\ |
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449 \bl{$A \rightarrow B :$} & \bl{$\{N_B-1\}_{K_{AB}}$}\\ |
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450 \end{tabular} |
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451 \end{center}\bigskip\pause |
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452 |
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453 but nothing is for free: then you need to synchronise time and possibly become victim to |
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454 timing attacks |
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455 |
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456 \end{frame}} |
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457 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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458 |
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459 |
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460 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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461 \mode<presentation>{ |
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462 \begin{frame}[c] |
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463 \frametitle{Binding Attacks} |
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464 |
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465 with public-private keys it is important that the public key is \alert{bound} |
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466 to the right owner (verified by a certification authority \bl{$CA$}) |
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467 |
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468 \begin{center} |
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469 \begin{tabular}{l} |
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470 \bl{$A \rightarrow CA :$} \bl{$A, B, N_A$}\\ |
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471 \bl{$CA \rightarrow A :$} \bl{$CA, \{CA, A, N_A, K^{pub}_{B}\}_{K^{pub}_{A}}$}\\ |
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472 \end{tabular} |
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473 \end{center}\bigskip |
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474 |
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475 \bl{$A$} knows \bl{$K^{priv}_A$} and can verify the message came from \bl{$CA$} |
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476 in response to \bl{$A$}'s message and trusts \bl{$K^{pub}_{B}$} is \bl{$B$}'s public key |
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477 |
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478 |
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479 \end{frame}} |
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480 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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481 |
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482 |
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483 |
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484 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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485 \mode<presentation>{ |
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486 \begin{frame}[c] |
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487 \frametitle{Binding Attacks} |
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488 |
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489 \begin{center} |
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490 \begin{tabular}{l} |
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491 \bl{$A \rightarrow I(CA) :$} \bl{$A, B, N_A$}\\ |
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492 \bl{$I(A) \rightarrow CA :$} \bl{$A, I, N_A$}\\ |
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493 \bl{$CA \rightarrow I(A) :$} \bl{$CA, \{CA, A, N_A, K^{pub}_{I}\}_{K^{pub}_{A}}$}\\ |
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494 \bl{$I(CA) \rightarrow A :$} \bl{$CA, \{CA, A, N_A, K^{pub}_{I}\}_{K^{pub}_{A}}$}\\ |
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495 \end{tabular} |
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496 \end{center}\pause |
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497 |
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498 \bl{$A$} now encrypts messages for \bl{$B$} with the public key of \bl{$I$} |
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499 (which happily decrypts them with its private key) |
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500 |
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501 \end{frame}} |
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502 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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503 |
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504 |
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505 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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506 \mode<presentation>{ |
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507 \begin{frame}[c] |
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508 |
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509 There are plenty of other protocols and attacks. This could go on ``forever''.\pause\bigskip |
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510 |
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511 We look here on one more kind of attacks that are because of a changing environment. |
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512 |
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513 \end{frame}} |
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514 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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515 |
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516 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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517 \mode<presentation>{ |
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518 \begin{frame}[t] |
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519 \frametitle{Changing Environment Attacks} |
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520 |
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521 \begin{itemize} |
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522 \item all protocols rely on some assumptions about the environment |
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523 (e.g., cryptographic keys cannot be broken)\bigskip\pause |
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524 \end{itemize} |
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525 |
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526 \only<2>{ |
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527 \begin{itemize} |
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528 \item in the ``good olden days'' (1960/70) rail transport was cheap, so fraud was not |
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529 worthwhile |
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530 \end{itemize}} |
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531 |
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532 \only<3>{ |
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533 \begin{itemize} |
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534 \item when it got expensive, some people bought cheaper monthly tickets for a suburban |
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535 station and a nearby one, and one for the destination and a nearby one |
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536 \item a large investment later all barriers were automatic and tickets could record state |
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537 \end{itemize}} |
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538 |
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539 \only<4>{ |
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540 \begin{itemize} |
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541 \item but suddenly the environment changed: rail transport got privatised creating many |
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542 competing companies |
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543 potentially cheating each other |
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544 \item revenue from monthly tickets was distributed according to a formula involving where the ticket was bought\ldots |
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545 \end{itemize}} |
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546 |
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547 \only<5>{ |
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548 \begin{itemize} |
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549 \item apart from bad outsiders (passengers), you also had bad insiders (rail companies) |
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550 \item chaos and litigation ensued |
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551 \end{itemize}} |
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552 |
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553 \end{frame}} |
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554 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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555 |
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556 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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557 \mode<presentation>{ |
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558 \begin{frame}[c] |
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559 |
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560 A Man-in-the-middle attack in real life: |
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561 |
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562 \begin{itemize} |
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563 \item the card only says yes or no to the terminal if the PIN is correct |
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564 \item trick the card in thinking transaction is verified by signature |
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565 \item trick the terminal in thinking the transaction was verified by PIN |
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566 \end{itemize} |
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567 |
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568 \begin{minipage}{1.1\textwidth} |
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569 \begin{center} |
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570 \mbox{}\hspace{-6mm}\includegraphics[scale=0.5]{pics/chip-attack.png} |
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571 \includegraphics[scale=0.3]{pics/chipnpinflaw.png} |
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572 \end{center} |
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573 \end{minipage} |
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574 |
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575 \end{frame}} |
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576 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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577 |
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578 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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579 \mode<presentation>{ |
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580 \begin{frame}[c] |
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581 \frametitle{Problems with EMV} |
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582 |
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583 \begin{itemize} |
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584 \item it is a wrapper for many protocols |
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585 \item specification by consensus (resulted unmanageable complexity) |
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586 \item its specification is 700 pages in English plus 2000+ pages for testing, additionally some |
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587 further parts are secret |
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588 \item other attacks have been found |
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589 |
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590 \item one solution might be to require always online verification of the PIN with the bank |
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591 \end{itemize} |
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592 |
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593 \end{frame}} |
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594 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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595 |
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596 |
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597 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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598 \mode<presentation>{ |
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599 \begin{frame}[c] |
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600 \frametitle{Problems with WEP (Wifi)} |
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601 |
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602 \begin{itemize} |
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603 \item a standard ratified in 1999 |
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604 \item the protocol was designed by a committee not including cryptographers |
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605 \item it used the RC4 encryption algorithm which is a stream cipher requiring a unique nonce |
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606 \item WEP did not allocate enough bits for the nonce |
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607 \item for authenticating packets it used CRC checksum which can be easily broken |
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608 \item the network password was used to directly encrypt packages (instead of a key negotiation protocol)\bigskip |
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609 \item encryption was turned of by default |
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610 \end{itemize} |
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611 |
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612 \end{frame}} |
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613 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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614 |
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615 |
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616 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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617 \mode<presentation>{ |
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618 \begin{frame}[c] |
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619 \frametitle{Protocols are Difficult} |
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620 |
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621 \begin{itemize} |
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622 \item even the systems designed by experts regularly fail\medskip |
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623 \item try to make everything explicit (you need to authenticate all data you might rely on)\medskip |
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624 \item the one who can fix a system should also be liable for the losses\medskip |
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625 \item cryptography is often not {\bf the} answer\bigskip\bigskip |
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626 \end{itemize} |
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627 |
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628 logic is one way protocols are studied in academia |
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629 (you can use computers to search for attacks) |
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630 |
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631 \end{frame}} |
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632 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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633 |
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634 |
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635 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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636 \mode<presentation>{ |
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637 \begin{frame}[c] |
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638 \frametitle{Public-Key Infrastructure} |
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639 |
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640 \begin{itemize} |
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641 \item the idea is to have a certificate authority (CA) |
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642 \item you go to the CA to identify yourself |
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643 \item CA: ``I, the CA, have verified that public key \bl{$P^{pub}_{Bob}$} belongs to Bob''\bigskip |
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644 \item CA must be trusted by everybody |
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645 \item What happens if CA issues a false certificate? Who pays in case of loss? (VeriSign |
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646 explicitly limits liability to \$100.) |
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647 \end{itemize} |
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648 |
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649 \end{frame}} |
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650 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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651 |
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652 |
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653 |
148 |
654 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
149 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
655 \mode<presentation>{ |
150 \mode<presentation>{ |
656 \begin{frame}[c] |
151 \begin{frame}[c] |
657 \frametitle{Privacy, Anonymity et al} |
152 \frametitle{Privacy, Anonymity et al} |
735 \end{textblock} |
230 \end{textblock} |
736 |
231 |
737 \end{frame}} |
232 \end{frame}} |
738 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
233 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
739 |
234 |
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235 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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236 \mode<presentation>{ |
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237 \begin{frame}[t] |
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238 \frametitle{Privacy} |
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239 |
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240 \begin{minipage}{1.05\textwidth} |
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241 \begin{itemize} |
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242 \item we \alert{do} want that government data is made public (free maps for example) |
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243 \item we \alert{do not} want that medical data becomes public (similarly tax data, school |
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244 records, job offers)\bigskip |
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245 \item personal information can potentially lead to fraud |
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246 (identity theft) |
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247 \end{itemize}\pause |
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248 |
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249 {\bf ``The reality'':} |
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250 \only<2>{\begin{itemize} |
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251 \item London Health Programmes lost in June last year unencrypted details of more than 8 million people |
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252 (no names, but postcodes and details such as gender, age and ethnic origin) |
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253 \end{itemize}} |
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254 \only<3>{\begin{itemize} |
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255 \item also in June last year, Sony got hacked: over 1M users' personal information, including passwords, email addresses, home addresses, dates of birth, and all Sony opt-in data associated with their accounts. |
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256 \end{itemize}} |
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257 \end{minipage} |
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258 |
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259 \end{frame}} |
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260 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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261 |
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262 |
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263 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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264 \mode<presentation>{ |
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265 \begin{frame}[c] |
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266 \frametitle{Privacy and Big Data} |
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267 |
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268 Selected sources of ``Big Data'':\smallskip{} |
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269 |
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270 \begin{itemize} |
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271 \item Facebook |
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272 \begin{itemize} |
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273 \item 40+ Billion photos (100 PB) |
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274 \item 6 Billion messages daily (5 - 10 TB) |
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275 \item 900 Million users |
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276 \end{itemize} |
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277 \item Common Crawl |
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278 \begin{itemize} |
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279 \item covers 3.8 Billion webpages (2012 dataset) |
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280 \item 50 TB of data |
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281 \end{itemize} |
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282 \item Google |
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283 \begin{itemize} |
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284 \item 20 PB daily (2008) |
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285 \end{itemize} |
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286 \item Twitter |
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287 \begin{itemize} |
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288 \item 7 Million users in the UK |
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289 \item a company called Datasift is allowed to mine all tweets since 2010 |
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290 \item they charge 10k per month for other companies to target advertisement |
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291 \end{itemize} |
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292 \end{itemize}\pause |
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293 |
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294 |
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295 \end{frame}} |
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296 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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297 |
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298 |
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299 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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300 \mode<presentation>{ |
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301 \begin{frame}[c] |
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302 \frametitle{Cookies\ldots} |
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303 |
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304 ``We have published a new cookie policy. It explains what cookies are |
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305 and how we use them on our site. To learn more about cookies and |
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306 their benefits, please view our cookie policy.\medskip |
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307 |
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308 If you'd like to disable cookies on this device, please view our information |
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309 pages on 'How to manage cookies'. Please be aware that parts of the |
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310 site will not function correctly if you disable cookies. \medskip |
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311 |
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312 By closing this |
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313 message, you consent to our use of cookies on this device in accordance |
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314 with our cookie policy unless you have disabled them.'' |
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315 |
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316 |
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317 \end{frame}} |
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318 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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319 |
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320 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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321 \mode<presentation>{ |
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322 \begin{frame}[c] |
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323 \frametitle{Scare Tactics} |
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324 |
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325 The actual policy reads:\bigskip |
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326 |
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327 ``As we explain in our Cookie Policy, cookies help you to get the most |
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328 out of our websites.\medskip |
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329 |
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330 If you do disable our cookies you may find that certain sections of our |
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331 website do not work. For example, you may have difficulties logging in |
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332 or viewing articles.'' |
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333 |
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334 |
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335 |
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336 |
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337 \end{frame}} |
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338 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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339 |
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340 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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341 \mode<presentation>{ |
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342 \begin{frame}[c] |
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343 \frametitle{Netflix Prize} |
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344 |
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345 Anonymity is \alert{necessary} for privacy, but \alert{not} enough!\bigskip |
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346 |
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347 \begin{itemize} |
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348 \item Netflix offered in 2006 (and every year until 2010) a 1 Mio \$ prize for improving their movie rating algorithm |
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349 \item dataset contained 10\% of all Netflix users (appr.~500K) |
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350 \item names were removed, but included numerical ratings as well as times of rating |
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351 \item some information was \alert{perturbed} (i.e., slightly modified) |
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352 \end{itemize} |
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353 |
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354 \hfill{\bf\alert{All OK?}} |
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355 |
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356 \end{frame}} |
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357 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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358 |
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359 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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360 \mode<presentation>{ |
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361 \begin{frame}[c] |
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362 \frametitle{Re-identification Attack} |
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363 |
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364 Two researchers analysed the data: |
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365 |
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366 \begin{itemize} |
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367 \item with 8 ratings (2 of them can be wrong) and corresponding dates that can have a margin 14-day error, 98\% of the |
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368 records can be identified |
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369 \item for 68\% only two ratings and dates are sufficient (for movie ratings outside the top 500)\bigskip\pause |
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370 \item they took 50 samples from IMDb (where people can reveal their identity) |
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371 \item 2 of them uniquely identified entries in the Netflix database (either by movie rating or by dates) |
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372 \end{itemize} |
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373 |
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374 \end{frame}} |
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375 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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376 |
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377 |
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378 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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379 \mode<presentation>{ |
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380 \begin{frame}[c] |
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381 \frametitle{} |
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382 |
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383 \begin{itemize} |
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384 \item Birth data, postcode and gender (unique for\\ 87\% of the US population) |
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385 \item Preferences in movies (99\% of 500K for 8 ratings) |
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386 \end{itemize}\bigskip |
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387 |
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388 Therefore best practices / or even law (HIPAA, EU): |
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389 |
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390 \begin{itemize} |
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391 \item only year dates (age group for 90 years or over), |
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392 \item no postcodes (sector data is OK, similarly in the US)\\ |
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393 \textcolor{gray}{no names, addresses, account numbers, licence plates} |
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394 \item disclosure information needs to be retained for 5 years |
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395 \end{itemize} |
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396 |
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397 \end{frame}} |
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398 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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399 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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400 \mode<presentation>{ |
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401 \begin{frame}<2>[c] |
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402 \frametitle{How to Safely Disclose Information?} |
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403 |
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404 \only<1>{ |
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405 \begin{itemize} |
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406 \item Assume you make a survey of 100 randomly chosen people. |
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407 \item Say 99\% of the surveyed people in the 10 - 40 age group have seen the |
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408 Gangnam video on youtube.\bigskip |
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409 |
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410 \item What can you infer about the rest of the population? |
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411 \end{itemize}} |
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412 \only<2>{ |
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413 \begin{itemize} |
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414 \item Is it possible to re-identify data later, if more data is released. \bigskip\bigskip\pause |
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415 |
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416 \item Not even releasing only aggregate information prevents re-identification attacks. |
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417 (GWAS was a public database of gene-frequency studies linked to diseases; |
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418 you only needed partial DNA information in order |
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419 to identify whether an individual was part of the study --- DB closed in 2008) |
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420 \end{itemize}} |
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421 |
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422 \end{frame}} |
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423 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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424 |
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425 |
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426 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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427 \mode<presentation>{ |
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428 \begin{frame}[c] |
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429 \frametitle{Differential Privacy} |
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430 |
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431 \begin{center} |
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432 User\;\;\;\; |
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433 \begin{tabular}{c} |
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434 tell me \bl{$f(x)$} $\Rightarrow$\\ |
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435 $\Leftarrow$ \bl{$f(x) + \text{noise}$} |
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436 \end{tabular} |
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437 \;\;\;\;\begin{tabular}{@{}c} |
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438 Database\\ |
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439 \bl{$x_1, \ldots, x_n$} |
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440 \end{tabular} |
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441 \end{center} |
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442 |
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443 |
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444 \begin{itemize} |
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445 \item \bl{$f(x)$} can be released, if \bl{$f$} is insensitive to |
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446 individual entries \bl{$x_1, \ldots, x_n$}\\ |
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447 \item Intuition: whatever is learned from the dataset would be learned regardless of whether |
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448 \bl{$x_i$} participates\bigskip\pause |
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449 |
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450 \item Noised needed in order to prevent queries:\\ Christian's salary $=$ |
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451 \begin{center} |
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452 \bl{\large$\Sigma$} all staff $-$ \bl{\large$\Sigma$} all staff $\backslash$ Christian |
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453 \end{center} |
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454 \end{itemize} |
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455 |
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456 \end{frame}} |
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457 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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458 |
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459 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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460 \mode<presentation>{ |
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461 \begin{frame}[c] |
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462 \frametitle{Adding Noise} |
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463 |
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464 Adding noise is not as trivial as one would wish: |
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465 |
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466 \begin{itemize} |
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467 \item If I ask how many of three have seen the Gangnam video and get a result |
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468 as follows |
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469 |
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470 \begin{center} |
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471 \begin{tabular}{l|c} |
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472 Alice & yes\\ |
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473 Bob & no\\ |
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474 Charlie & yes\\ |
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475 \end{tabular} |
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476 \end{center} |
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477 |
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478 then I have to add a noise of \bl{$1$}. So answers would be in the |
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479 range of \bl{$1$} to \bl{$3$} |
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480 |
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481 \bigskip |
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482 \item But if I ask five questions for all the dataset (has seen Gangnam video, is male, below 30, \ldots), |
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483 then one individual can change the dataset by \bl{$5$} |
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484 \end{itemize} |
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485 |
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486 \end{frame}} |
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487 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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488 |
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489 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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490 \mode<presentation>{ |
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491 \begin{frame}[t] |
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492 \frametitle{\begin{tabular}{@{}c@{}}Tor\end{tabular}} |
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493 |
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494 \begin{itemize} |
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495 \item initially developed by US Navy Labs, but then opened up to the world |
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496 \item network of proxy nodes |
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497 \item a Tor client establishes a ``random'' path to the destination server (you cannot trace back where the information came from)\bigskip\pause |
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498 \end{itemize} |
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499 |
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500 \only<2>{ |
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501 \begin{itemize} |
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502 \item malicious exit node attack: someone set up 5 Tor exit nodes and monitored the traffic: |
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503 \begin{itemize} |
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504 \item a number of logons and passwords used by embassies (Usbekistan `s1e7u0l7c', while |
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505 Tunesia `Tunesia' and India `1234') |
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506 \end{itemize} |
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507 \end{itemize}} |
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508 \only<3>{ |
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509 \begin{itemize} |
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510 \item bad apple attack: if you have one insecure application, your IP can be tracked through Tor |
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511 \begin{itemize} |
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512 \item background: 40\% of traffic on Tor is generated by BitTorrent |
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513 \end{itemize} |
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514 \end{itemize}} |
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515 |
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516 |
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517 \end{frame}} |
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518 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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519 |
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520 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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521 \mode<presentation>{ |
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522 \begin{frame}[t] |
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523 \frametitle{\begin{tabular}{@{}c@{}}Skype\end{tabular}} |
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524 |
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525 \begin{itemize} |
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526 \item Skype used to be known as a secure online communication (encryption cannot be disabled), |
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527 but \ldots\medskip |
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528 |
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529 \item it is impossible to verify whether crypto algorithms are correctly used, or whether there are backdoors.\bigskip |
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530 |
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531 \item recently someone found out that you can reset the password of somebody else's |
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532 account, only knowing their email address (needed to suspended the password reset feature temporarily) |
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533 \end{itemize} |
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534 |
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535 |
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536 \end{frame}} |
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537 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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538 |
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539 |
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540 |
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541 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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542 \mode<presentation>{ |
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543 \begin{frame}[c] |
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544 \frametitle{\begin{tabular}{@{}c@{}}Take Home Point\end{tabular}} |
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545 |
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546 According to Ross Anderson: \bigskip |
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547 \begin{itemize} |
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548 \item Privacy in a big hospital is just about doable.\medskip |
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549 \item How do you enforce privacy in something as big as Google |
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550 or complex as Facebook? No body knows.\bigskip |
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551 |
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552 Similarly, big databases imposed by government |
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553 \end{itemize} |
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554 |
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555 |
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556 \end{frame}} |
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557 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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558 |
740 |
559 |
741 \end{document} |
560 \end{document} |
742 |
561 |
743 %%% Local Variables: |
562 %%% Local Variables: |
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563 %%% mode: latex |