Hi Kim: I'm trying to convert the caam driver to the new AEAD interface. I've run into some weird code in the GCM implementation. The function gcm_set_sh_desc handles generic GCM and it does some pretty hairy stuff with respect to zero-length AD and zero-length cryptlen. It appears to be avoiding doing a zero-length seq fifo load by checking the length before each operation. So my question is is it forbidden to do a zero-length seq fifo load? If so what happens when you do it? This is important because none of the other AEAD implementations (e.g., RFC4543) check for zero lengths. With the new AEAD user-space interface it is quite easy to give a zero-length request to any AEAD algorithm. Also it appears that in caamhash we don't avoid doing zero-length seq fifo loads at all. And they obviously work because our very first selftest for SHA is a zero-length digest. So could it be that zero-length seq fifo loads do work but only work once? Or is it that seq fifo loads stop working after a previous seq fifo load reaches length zero? If so can you get around this by always adding some extra pading after the end of the sequence? Thanks, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- 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
