> > Essentially this is a way of turning a block cipher into a stream > > cipher. > This isn't standard CFB, its a variation using a block-cipher as a > keystream generator. And it just...might...work <insert evil laugh>.
This is pretty standard, really. It represents the situation where the "character size" is the same as the block size, which is a well defined case in standard CFB. Think of your message as being composed of 64 bit characters and doing CFB with a 64 bit block cipher. You seed the process with a 64 bit IV. Then as each 64 bit plaintext character comes in, you XOR with the encryption of the previous 64-bit ciphertext character to produce the new ciphertext character. Now, because of the order in which these operations are done, you can actually incrementally process each bit of the 64 bits of the plaintext character, since that is just an XOR with the encryption of the previous 64-bit ciphertext character. There is no need to buffer up 64 bits before handing them to the cipher. This is the procedure I outlined in my previous message. The result is exactly the same this way as if you did the buffering (except that the last block may be short). But it allows you to process things a character at a time, which gives you much more flexibility. Hal _______________________________________________ Freenet-dev mailing list Freenet-dev at lists.sourceforge.net http://lists.sourceforge.net/mailman/listinfo/freenet-dev
