Add HMAC-SHA256

src/crypto/hmac_sha256.cpp

@@ -0,0 +1,34 @@
+// 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/hmac_sha256.h"
+
+#include <string.h>
+
+CHMAC_SHA256::CHMAC_SHA256(const unsigned char* key, size_t keylen)
+{
+    unsigned char rkey[64];
+    if (keylen <= 64) {
+        memcpy(rkey, key, keylen);
+        memset(rkey + keylen, 0, 64 - keylen);
+    } else {
+        CSHA256().Write(key, keylen).Finalize(rkey);
+        memset(rkey + 32, 0, 32);
+    }
+
+    for (int n = 0; n < 64; n++)
+        rkey[n] ^= 0x5c;
+    outer.Write(rkey, 64);
+
+    for (int n = 0; n < 64; n++)
+        rkey[n] ^= 0x5c ^ 0x36;
+    inner.Write(rkey, 64);
+}
+
+void CHMAC_SHA256::Finalize(unsigned char hash[OUTPUT_SIZE])
+{
+    unsigned char temp[32];
+    inner.Finalize(temp);
+    outer.Write(temp, 32).Finalize(hash);
+}