Add the RFC6979 PRNG

src/crypto/rfc6979_hmac_sha256.cpp

@@ -0,0 +1,47 @@
+// Copyright (c) 2014 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "crypto/rfc6979_hmac_sha256.h"
+
+#include <string.h>
+
+#include <algorithm>
+
+static const unsigned char zero[1] = {0x00};
+static const unsigned char one[1] = {0x01};
+
+RFC6979_HMAC_SHA256::RFC6979_HMAC_SHA256(const unsigned char* key, size_t keylen, const unsigned char* msg, size_t msglen) : retry(false)
+{
+    memset(V, 0x01, sizeof(V));
+    memset(K, 0x00, sizeof(K));
+
+    CHMAC_SHA256(K, sizeof(K)).Write(V, sizeof(V)).Write(zero, sizeof(zero)).Write(key, keylen).Write(msg, msglen).Finalize(K);
+    CHMAC_SHA256(K, sizeof(K)).Write(V, sizeof(V)).Finalize(V);
+    CHMAC_SHA256(K, sizeof(K)).Write(V, sizeof(V)).Write(one, sizeof(one)).Write(key, keylen).Write(msg, msglen).Finalize(K);
+    CHMAC_SHA256(K, sizeof(K)).Write(V, sizeof(V)).Finalize(V);
+}
+
+RFC6979_HMAC_SHA256::~RFC6979_HMAC_SHA256()
+{
+    memset(V, 0x01, sizeof(V));
+    memset(K, 0x00, sizeof(K));
+}
+
+void RFC6979_HMAC_SHA256::Generate(unsigned char* output, size_t outputlen)
+{
+    if (retry) {
+        CHMAC_SHA256(K, sizeof(K)).Write(V, sizeof(V)).Write(zero, sizeof(zero)).Finalize(K);
+        CHMAC_SHA256(K, sizeof(K)).Write(V, sizeof(V)).Finalize(V);
+    }
+
+    while (outputlen > 0) {
+        CHMAC_SHA256(K, sizeof(K)).Write(V, sizeof(V)).Finalize(V);
+        size_t len = std::min(outputlen, sizeof(V));
+        memcpy(output, V, len);
+        output += len;
+        outputlen -= len;
+    }
+
+    retry = true;
+}