Externalize the state of a RFC 6979 nonce computation.

This lets you amortize quite a few memory allocations (RNG, various
BigInts, etc) over many nonce generations.

Change generate_rfc6979_nonce to just instantiate one of these states,
call the function once, and return. This doesn't have any additional
overhead versus the previous implementation of this function.

Fix HMAC_DRBG to correctly reset its state to its starting position
when you call clear() on it.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/lib/rng/hmac_drbg/hmac_drbg.h b/src/lib/rng/hmac_drbg/hmac_drbg.h
index b56e90fc4..979b754b2 100644
--- a/src/lib/rng/hmac_drbg/hmac_drbg.h
+++ b/src/lib/rng/hmac_drbg/hmac_drbg.h
@@ -1,6 +1,6 @@
 /*
 * HMAC_DRBG (SP800-90A)
-* (C) 2014 Jack Lloyd
+* (C) 2014,2015 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -33,7 +33,7 @@ class BOTAN_DLL HMAC_DRBG : public RandomNumberGenerator
       * @param underlying_rng RNG used generating inputs (eg HMAC_RNG)
       */
       HMAC_DRBG(MessageAuthenticationCode* mac,
-                RandomNumberGenerator* underlying_rng);
+                RandomNumberGenerator* underlying_rng = nullptr);
 
    private:
       void update(const byte input[], size_t input_len);