Re: IPSec hmac(sha256) truncation bits length

Hi Nicolae,

up to the Linux 2.6.32 kernel the SHA256 hash was erroneously truncated
to 96 bits. With Linux 2.6.33 the correct truncation to 128 bits
was introduce as well as the SHA384_192 and SHA512_256 data integrity
algorithms. If you want to apply the correct SHA2 truncation, use
XFRMA_ALG_AUTH_TRUNC instead of XFRMA_ALG_AUTH.

Best regards

Andreas

On 03/04/2015 06:13 PM, Nicolae Rosia wrote:

Hello,

I'm trying to understand why icv_truncbits is set to 96 for
hmac(sha256) in xfrm_algo.c because
RFC4868 [1] says that the truncation length for HMAC-SHA256 should be 128.
Am I looking in the wrong place?

[1] https://tools.ietf.org/html/rfc4868#section-2.6

Best regards,
Nicolae Rosia
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Andreas Steffen                         andreas.steffen@strongswan.org
strongSwan - the Open Source VPN Solution!          www.strongswan.org
Institute for Internet Technologies and Applications
University of Applied Sciences Rapperswil
CH-8640 Rapperswil (Switzerland)
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