From: Herbert Xu <herbert@gondor.apana.org.au>
To: Stephan Mueller <smueller@chronox.de>
Cc: linux-crypto@vger.kernel.org, David Howells <dhowells@redhat.com>,
Mat Martineau <mathew.j.martineau@linux.intel.com>,
keyrings@vger.kernel.org
Subject: Re: [PATCH v2 3/4] crypto: kdf - SP800-108 Key Derivation Function
Date: Thu, 2 Jun 2016 16:55:26 +0800 [thread overview]
Message-ID: <20160602085526.GA15919@gondor.apana.org.au> (raw)
In-Reply-To: <4593825.q48Y9K9RSZ@positron.chronox.de>
On Tue, May 31, 2016 at 01:52:32PM +0200, Stephan Mueller wrote:
>
> + * NOTE: Technically you can use one buffer for holding the label_context and
> + * the outbuf in the example above. Howerver, multiple rounds of the
> + * KDF are to be expected with the input must always be the same.
> + * The first round would replace the input in case of one buffer, and the
> + * KDF would calculate a cryptographically strong result which, however,
> + * is not portable to other KDF implementations! Thus, always use
> + * different buffers for the label_context and the outbuf. A safe
> + * in-place operation can only be done when only one round of the KDF
> + * is executed (i.e. the size of the requested buffer is equal to the
> + * digestsize of the used MAC).
Why don't you put the result in a temporary buffer and then copy
it? These things are tiny, right?
Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2016-06-02 8:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-31 11:50 [PATCH v2 0/4] crypto: Key Derivation Function (SP800-108) Stephan Mueller
2016-05-31 11:51 ` [PATCH v2 1/4] crypto: add template handling for RNGs Stephan Mueller
2016-05-31 11:52 ` [PATCH v2 2/4] crypto: kdf - add known answer tests Stephan Mueller
2016-05-31 11:52 ` [PATCH v2 3/4] crypto: kdf - SP800-108 Key Derivation Function Stephan Mueller
2016-06-02 8:55 ` Herbert Xu [this message]
2016-06-02 15:12 ` Stephan Mueller
2016-06-08 3:13 ` Herbert Xu
2016-06-08 4:58 ` Stephan Mueller
2016-05-31 11:53 ` [PATCH v2 4/4] crypto: kdf - enable compilation Stephan Mueller
2016-06-02 8:56 ` [PATCH v2 0/4] crypto: Key Derivation Function (SP800-108) Herbert Xu
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