On Fri, 2007-08-17 at 10:19 +0800, Herbert Xu wrote: > Joy Latten <latten@xxxxxxxxxxxxxx> wrote: > > I am in learning mode and have been looking into CTR. > > Based on the fact that CTR does not require the plaintext to > > be a multiple of the blocksize nor is padding required, > > should I use cipher.c routines (as xcbc does) instead > > of blkcipher.c routines (as cbc does)? > > (I've been referencing rfc 3686.) > > CBC is the correct model to follow. For our purposes you > will only get multiples of blocks. The only difference > is that unlike CBC you can chop bits off the last block > of plain text and the same bits will be chopped off in > the cipher text. > ok, that is good, I started out following CBC model and will continue. Just to make sure I understand correctly, our plaintext will be a multiple of the blocksize, therefore it may be padded, right? Also, since it is a multiple, I don't have to worry about last block of plaintext being less than blocksize and truncating the keystream or ciphertext, right? Thanks. Joy > With CBC chopping off bits in either changes the other one > entirely. > > Cheers, - To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
