Re: [math-fun] a simple/stupid point about AES and other block cryptosystems

If you encrypt a character stream (1 char = 1 byte) going block by block (same key each block) then you are going to repeat if and when author repeats a 16-character phrase....

This is a simple/stupid point, but I have not seen it mentioned in crypto manuals!

Then you have been reading the wrong "crypto manuals". It's a very, very standard observation that using a block cipher independently on each block of the message is a Very Bad Idea; see e.g. http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation -- g