[RFC PATCH 2/3] Add API for initializing AEAD modes

Werner Koch wk at gnupg.org
Wed Oct 16 15:18:32 CEST 2013

On Wed, 16 Oct 2013 13:26, jussi.kivilinna at iki.fi said:

> I started writing following example to check is for CCM would work with
> these. Problem here is that CCM needs authentication tag length for
> first CBC-MAC block. Maybe taglen could be given to CCM mode encryption
> with gcry_cipher_settag(hd, NULL, taglen)?

Yes, I think this is okay.

> With OCB, if AAD stays the same between messages, one can reuse the 
> preprocessed HASH(Key, AAD). Following example would process three messages,
> where first two have same AAD and last one has zero length AAD. Does this
> look ok?

Yes.  We may eventually put such examples into the manual.



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