13 \item Imagine you have an completely `innocent' email message, 

    13 \item Imagine you have an completely `innocent' email message,

    14   like birthday wishes to your grandmother? Why should you

    14       like birthday wishes to your grandmother? Why should you

    15   still encrypt this message and your grandmother take the

    15       still encrypt this message and your grandmother take the

    16     effort to decrypt it? 

    16       effort to decrypt it? 

    17 

    18 \item One part of achieving privacy (but not the only one) is

    19       to properly encrypt your conversations on the Internet.

    20       But this is fiercely resisted by some spy agencies.

    21       These agencies (and some politicians for that

    22       matter) argue that, for example, ISIL's recruiters

    23       broadcast messages on, say, Twitter, and get people to

    24       follow them. Then they move potential recruits to

    25       Twitter Direct Messaging to evaluate if they are a

    26       legitimate recruit. If yes, they move them to an

    27       encrypted mobile-messaging app. The spy agencies argue

    28       that although they can follow the conversations on

    29       Twitter, they ``go dark'' on the encrypted message

    30       app. To counter this ``going-dark problem'', the spy

    31       agencies push for the implementation of back-doors in

    32       iMessage and Facebook and Skype and everything else UK

    33       or US-made, which they can use eavesdrop on

    34       conversations without the conversants' knowledge or

    35       consent.\medskip

    36    

    37       What is the fallacy in the spy agencies going-dark

    38       argument? (Hint: Think what would happen if the spy

    39       agencies and certain politicians get their wish.)

    40