[git] GCRYPT - branch, master, updated. libgcrypt-1.5.0-380-g7d91e99

[by Christian Grothoff]

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- Log -----------------------------------------------------------------
commit 7d91e99bcd30a463dd4faed014b8521a663d8316
Author: Christian Grothoff <christian at grothoff.org>
Date:   Mon Nov 11 16:04:30 2013 +0100

    ecc: Fix key generation for a plain Ed25519 key.
    
    * cipher/ecc.c (nist_generate_key): Use custom code for ED25519.
    --
    
    I wish there would a an RFC for Curve25519 - the description in the
    paper is easy to misunderstand for a non-mathematician.  Source code
    and a paper are nice but a proper description (like those in the HAC)
    would be better.  Problem spotted by Florian Dold.
    
    Signed-off-by: Werner Koch <wk at gnupg.org>

diff --git a/cipher/ecc.c b/cipher/ecc.c
index 9135b68..72ca726 100644
--- a/cipher/ecc.c
+++ b/cipher/ecc.c
@@ -145,7 +145,21 @@ nist_generate_key (ECC_secret_key *sk, elliptic_curve_t *E, mpi_ec_t ctx,
   point_init (&Q);
 
   /* Generate a secret.  */
-  sk->d = _gcry_dsa_gen_k (E->n, random_level);
+  if (ctx->dialect == ECC_DIALECT_ED25519)
+    {
+      char *rndbuf;
+
+      sk->d = mpi_snew (256);
+      rndbuf = gcry_random_bytes_secure (32, random_level);
+      rndbuf[0] &= 0x7f;  /* Clear bit 255. */
+      rndbuf[0] |= 0x40;  /* Set bit 254.   */
+      rndbuf[31] &= 0xf8; /* Clear bits 2..0 so that d mod 8 == 0  */
+      _gcry_mpi_set_buffer (sk->d, rndbuf, 32, 0);
+      gcry_free (rndbuf);
+    }
+  else
+    sk->d = _gcry_dsa_gen_k (E->n, random_level);
+
 
   /* Compute Q.  */
   _gcry_mpi_ec_mul_point (&Q, sk->d, &E->G, ctx);

-----------------------------------------------------------------------

Summary of changes:
 cipher/ecc.c |   16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)


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