2 This file is part of GNUnet.
3 (C) 2010 Christian Grothoff (and other contributing authors)
5 GNUnet is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 2, or (at your
8 option) any later version.
10 GNUnet is distributed in the hope that it will be useful, but
11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with GNUnet; see the file COPYING. If not, write to the
17 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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22 * @file src/util/crypto_kdf.c
23 * @brief Key derivation
30 #include "gnunet_crypto_lib.h"
34 * @param result buffer for the derived key, allocated by caller
35 * @param out_len desired length of the derived key
37 * @param xts_len length of xts
38 * @param skm source key material
39 * @param skm_len length of skm
40 * @param argp va_list of void * & size_t pairs for context chunks
41 * @return GNUNET_YES on success
44 GNUNET_CRYPTO_kdf_v (void *result, const unsigned long long out_len,
45 const void *xts, const size_t xts_len, const void *skm,
46 const size_t skm_len, const va_list argp)
49 "Finally, we point out to a particularly advantageous instantiation using
50 HMAC-SHA512 as XTR and HMAC-SHA256 in PRF* (in which case the output from SHA-512 is
51 truncated to 256 bits). This makes sense in two ways: First, the extraction part is where we need a
52 stronger hash function due to the unconventional demand from the hash function in the extraction
53 setting. Second, as shown in Section 6, using HMAC with a truncated output as an extractor
54 allows to prove the security of HKDF under considerably weaker assumptions on the underlying
57 http://eprint.iacr.org/2010/264
60 return GNUNET_CRYPTO_hkdf_v (result, out_len, GCRY_MD_SHA512, GCRY_MD_SHA256,
61 xts, xts_len, skm, skm_len, argp);
66 * @param result buffer for the derived key, allocated by caller
67 * @param out_len desired length of the derived key
69 * @param xts_len length of xts
70 * @param skm source key material
71 * @param skm_len length of skm
72 * @param ... void * & size_t pairs for context chunks
73 * @return GNUNET_YES on success
76 GNUNET_CRYPTO_kdf (void *result, const unsigned long long out_len,
77 const void *xts, const size_t xts_len, const void *skm,
78 const size_t skm_len, ...)
83 va_start(argp, skm_len);
84 ret = GNUNET_CRYPTO_kdf_v (result, out_len, xts, xts_len, skm, skm_len, argp);