GNUnet  0.11.x
Macros | Functions
crypto_kdf.c File Reference

Key derivation. More...

#include <gcrypt.h>
#include "platform.h"
#include "gnunet_crypto_lib.h"
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Macros

#define LOG(kind, ...)   GNUNET_log_from (kind, "util-crypto-kdf", __VA_ARGS__)
 

Functions

enum GNUNET_GenericReturnValue GNUNET_CRYPTO_kdf_v (void *result, size_t out_len, const void *xts, size_t xts_len, const void *skm, size_t skm_len, va_list argp)
 Derive key. More...
 
enum GNUNET_GenericReturnValue GNUNET_CRYPTO_kdf (void *result, size_t out_len, const void *xts, size_t xts_len, const void *skm, size_t skm_len,...)
 Derive key. More...
 
void GNUNET_CRYPTO_kdf_mod_mpi (gcry_mpi_t *r, gcry_mpi_t n, const void *xts, size_t xts_len, const void *skm, size_t skm_len, const char *ctx)
 Deterministically generate a pseudo-random number uniformly from the integers modulo a libgcrypt mpi. More...
 

Detailed Description

Key derivation.

Author
Nils Durner
Jeffrey Burdges burdg.nosp@m.es@g.nosp@m.nunet.nosp@m..org

Definition in file crypto_kdf.c.

Macro Definition Documentation

◆ LOG

#define LOG (   kind,
  ... 
)    GNUNET_log_from (kind, "util-crypto-kdf", __VA_ARGS__)

Definition at line 33 of file crypto_kdf.c.

Function Documentation

◆ GNUNET_CRYPTO_kdf_v()

enum GNUNET_GenericReturnValue GNUNET_CRYPTO_kdf_v ( void *  result,
size_t  out_len,
const void *  xts,
size_t  xts_len,
const void *  skm,
size_t  skm_len,
va_list  argp 
)

Derive key.

Parameters
resultbuffer for the derived key, allocated by caller
out_lendesired length of the derived key
xtssalt
xts_lenlength of xts
skmsource key material
skm_lenlength of skm
argpva_list of void * & size_t pairs for context chunks
Returns
GNUNET_YES on success

Definition at line 1 of file crypto_kdf.c.

44 {
45  /*
46  * "Finally, we point out to a particularly advantageous instantiation using
47  * HMAC-SHA512 as XTR and HMAC-SHA256 in PRF* (in which case the output from SHA-512 is
48  * truncated to 256 bits). This makes sense in two ways: First, the extraction part is where we need a
49  * stronger hash function due to the unconventional demand from the hash function in the extraction
50  * setting. Second, as shown in Section 6, using HMAC with a truncated output as an extractor
51  * allows to prove the security of HKDF under considerably weaker assumptions on the underlying
52  * hash function."
53  *
54  * http://eprint.iacr.org/2010/264
55  */
57  out_len,
58  GCRY_MD_SHA512,
59  GCRY_MD_SHA256,
60  xts,
61  xts_len,
62  skm,
63  skm_len,
64  argp);
65 }
static int result
Global testing status.
enum GNUNET_GenericReturnValue GNUNET_CRYPTO_hkdf_v(void *result, size_t out_len, int xtr_algo, int prf_algo, const void *xts, size_t xts_len, const void *skm, size_t skm_len, va_list argp)
Derive key.
Definition: crypto_hkdf.c:165

Referenced by GNUNET_CRYPTO_hmac_derive_key_v(), and GNUNET_CRYPTO_symmetric_derive_iv_v().

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◆ GNUNET_CRYPTO_kdf_mod_mpi()

void GNUNET_CRYPTO_kdf_mod_mpi ( gcry_mpi_t *  r,
gcry_mpi_t  n,
const void *  xts,
size_t  xts_len,
const void *  skm,
size_t  skm_len,
const char *  ctx 
)

Deterministically generate a pseudo-random number uniformly from the integers modulo a libgcrypt mpi.

Parameters
[out]rMPI value set to the FDH
nMPI to work modulo
xtssalt
xts_lenlength of xts
skmsource key material
skm_lenlength of skm
ctxcontext string

Definition at line 94 of file crypto_kdf.c.

99 {
100  gcry_error_t rc;
101  unsigned int nbits;
102  size_t rsize;
103  uint16_t ctr;
104 
105  nbits = gcry_mpi_get_nbits (n);
106  /* GNUNET_assert (nbits > 512); */
107  ctr = 0;
108  while (1)
109  {
110  /* Ain't clear if n is always divisible by 8 */
111  size_t bsize = (nbits - 1) / 8 + 1;
112  uint8_t buf[bsize];
113  uint16_t ctr_nbo = htons (ctr);
114 
115  rc = GNUNET_CRYPTO_kdf (buf,
116  bsize,
117  xts, xts_len,
118  skm, skm_len,
119  ctx, strlen (ctx),
120  &ctr_nbo, sizeof(ctr_nbo),
121  NULL, 0);
122  GNUNET_assert (GNUNET_YES == rc);
123  rc = gcry_mpi_scan (r,
124  GCRYMPI_FMT_USG,
125  (const unsigned char *) buf,
126  bsize,
127  &rsize);
128  GNUNET_assert (GPG_ERR_NO_ERROR == rc); /* Allocation error? */
129  GNUNET_assert (rsize == bsize);
130  gcry_mpi_clear_highbit (*r,
131  nbits);
132  GNUNET_assert (0 ==
133  gcry_mpi_test_bit (*r,
134  nbits));
135  ++ctr;
136  /* We reject this FDH if either *r > n and retry with another ctr */
137  if (0 > gcry_mpi_cmp (*r, n))
138  break;
139  gcry_mpi_release (*r);
140  }
141 }
static char buf[2048]
static unsigned int bsize
static struct GNUNET_DNSSTUB_Context * ctx
Context for DNS resolution.
@ GNUNET_YES
Definition: gnunet_common.h:97
enum GNUNET_GenericReturnValue GNUNET_CRYPTO_kdf(void *result, size_t out_len, const void *xts, size_t xts_len, const void *skm, size_t skm_len,...)
Derive key.
Definition: crypto_kdf.c:69
#define GNUNET_assert(cond)
Use this for fatal errors that cannot be handled.

References bsize, buf, ctx, GNUNET_assert, GNUNET_CRYPTO_kdf(), and GNUNET_YES.

Referenced by cs_full_domain_hash(), GNUNET_CRYPTO_rsa_blind(), and rsa_blinding_key_derive().

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