On Apr 11, 2013, at 8:37 PM, "Manger, James H" 
<[email protected]> wrote:

> Karen,
> I think this poll conflates 2 issues: a) making the integrity check value 
> part of the ciphertext (as per RFC 5116); and b) not treating the IV in 
> CBC-HMAC as an (app-supplied) AEAD nonce, but as part of the randomized 
> (crypto-library-supplied) ciphertext (as per 
> draft-mcgrew-aead-aes-cbc-hmac-sha2).
> 
> RFC 5116 “An interface and algorithms for authenticated encryption” has a 
> nonce (N) and a separate field to the ciphertext. N is a separate input to 
> the encryption and decryption operations.
> draft-mcgrew-aead-aes-cbc-hmac-sha2 defines AEAD algorithms that take a 
> zero-length nonce, but prefix the ciphertext with a random IV.
> 
> 
> So my answer to the poll:
> 
> 2b.
> Switch to using RFC 5116.
> A JWE should have separate nonce and ciphertext fields (but no separate 
> integrity value field).
> JWE should use the term “nonce”, instead of “initialization vector”.
> Any integrity value that an algorithm creates should be part of the 
> ciphertext.
> When draft-mcgrew-aead-aes-cbc-hmac-sha2 is used as the AEAD algorithm the 
> nonce field will be empty, and the ciphertext field will be a concatenation 
> of an IV, AES output, and the truncated HMAC output.
> 

My preference is also this 2b (or would it be 3?).


- m&m

Matt Miller < [email protected] >
Cisco Systems, Inc.

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