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Date: Wed, 8 Jul 2015 14:00:57 +0530 From: Lokesh Vutla <lokeshvutla@...com> To: Herbert Xu <herbert@...dor.apana.org.au> CC: <linux-crypto@...r.kernel.org>, <davem@...emloft.net>, <linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <t-kristo@...com>, <nsekhar@...com> Subject: Re: [PATCH v2 6/7] crypto: omap-aes: Add support for GCM mode On Wednesday 08 July 2015 01:23 PM, Herbert Xu wrote: > On Wed, Jul 08, 2015 at 03:48:05PM +0800, Herbert Xu wrote: >> On Wed, Jul 08, 2015 at 12:29:47PM +0530, Lokesh Vutla wrote: >>> >>>>> + if (req->assoclen + req->cryptlen == 0) { >>>>> + scatterwalk_map_and_copy(ctx->auth_tag, req->dst, 0, authlen, >>>>> + 1); >>>>> + return 0; >>>>> + } >>>> >>>> How can this be right? Did you enable the selftest? >>> Why not? Self tests are passed for this case. >>> >>> As per the equation given in GCM spec[1], we can see that >>> if assoclen and cryptlen is 0, then output of GCM is just E(K, Y0) >>> where Y0 = IV||(0^31)1 >>> I have E(K, Y0) calculated in previous step. And copying it >>> to destination if assoclen and cryptlen is 0. >>> >>> Correct me if I am wrong. >> >> It should be E(K, Y0) ^ GHASH(0). So unless GHASH(0) == 0, your >> code doesn't work. > > OK, GHASH(0) is indeed zero so I guess your code does work after > all. Sorry. I did not see this message and replied on the other thread. Thanks and regards, Lokesh > > Cheers, > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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