Re: [Cfrg] Use of authenticated encryption for key wrapping
"David McGrew (mcgrew)" <mcgrew@cisco.com> Mon, 18 March 2013 13:24 UTC
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From: "David McGrew (mcgrew)" <mcgrew@cisco.com>
To: "Brian Weis (bew)" <bew@cisco.com>, "jose@ietf.org" <jose@ietf.org>, "cfrg@ietf.org" <cfrg@ietf.org>
Thread-Topic: [Cfrg] Use of authenticated encryption for key wrapping
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Date: Mon, 18 Mar 2013 13:24:13 +0000
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Subject: Re: [Cfrg] Use of authenticated encryption for key wrapping
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Hi Brian, On 3/15/13 11:42 AM, "Brian Weis (bew)" <bew@cisco.com> wrote: >Jim Schaad gave a presentation on JOSE to CFRG today >(<http://www.ietf.org/proceedings/86/slides/slides-86-cfrg-5.pdf>). The >question came up as to whether AES key wrap was necessarily the only >method that was safe for key wrapping in JOSE. The other algorithm under >consideration is AES-GCM. > >Section 3.1 of NIST 800-38F (Methods for Key Wrapping) says: > >"Previously approved authenticated-encryption modes‹as well as >combinations of an approved encryption mode with an approved >authentication method‹are approved for the protection of cryptographic >keys, in addition to general data." > >So if one considers that to be good enough advice, AES-GCM would indeed >be an acceptable method of key wrapping. The chairs asked me to >cross-post this for discussion. Thanks for sending out the pointer. I think the biggest negative with using AES-GCM for key wrapping is that GCM is not designed to be misuse-resistant. In contrast, the AES-KW algorithm does provide some misuse resistance: the AES-KW encryption algorithm does not require that the caller provide a distinct nonce for each invocation. The biggest negative with requiring the use of AES-KW for key wrapping is that, it requires the implementation of the AES decryption operation (unlike GCM), it is yet another algorithm to implement/test/validate, and it takes up space that is precious in a constrained environment. NIST is right to allow other authenticated encryption methods than AES-KW to be used for key wrapping. But if AES-KW is available for JOSE, then it makes sense to use it for key wrapping. My $0.02. David > >Brian >_______________________________________________ >Cfrg mailing list >Cfrg@irtf.org >http://www.irtf.org/mailman/listinfo/cfrg
- [Cfrg] Use of authenticated encryption for key wr… Brian Weis
- Re: [Cfrg] [jose] Use of authenticated encryption… Russ Housley
- Re: [Cfrg] [jose] Use of authenticated encryption… John Bradley
- Re: [Cfrg] Use of authenticated encryption for ke… David McGrew (mcgrew)
- Re: [Cfrg] Use of authenticated encryption for ke… Dan Harkins