Add HMAC-SHA256

src/crypto/hmac_sha256.h

@@ -0,0 +1,32 @@
+// 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.
+
+#ifndef BITCOIN_HMAC_SHA256_H
+#define BITCOIN_HMAC_SHA256_H
+
+#include "crypto/sha256.h"
+
+#include <stdint.h>
+#include <stdlib.h>
+
+/** A hasher class for HMAC-SHA-512. */
+class CHMAC_SHA256
+{
+private:
+    CSHA256 outer;
+    CSHA256 inner;
+
+public:
+    static const size_t OUTPUT_SIZE = 32;
+
+    CHMAC_SHA256(const unsigned char* key, size_t keylen);
+    CHMAC_SHA256& Write(const unsigned char* data, size_t len)
+    {
+        inner.Write(data, len);
+        return *this;
+    }
+    void Finalize(unsigned char hash[OUTPUT_SIZE]);
+};
+
+#endif // BITCOIN_SHA256_H