Re: Electronic Codebook

 <s_4@wp.pl> wrote:
>Some criminal, who can modifity content of incrypted messages (banks'
>transfers), make a 17 transfers to his own bank account, allways on the
>same amount (sum). Then he searching in sending messages, such
>incrypted number of bank account, which were send exactly 17 times and
>on the same amount (sum). He recognize incrypted version of his no.
>bank account, despite he doesn't know the key. Why he have to make 17
>transfers?

You have not given enough information to answer the questions
(especially about the number 17). What is the format of the messages
sent, what is the block size, etc.

My guess is that if you clearly spell out what the messages are and
how they are encrypted, you will see the answer yourself.

-- 
Kristian Gjøsteen