diff --git a/src/Makefile.am b/src/Makefile.am
index e1e6915185..1a5c57a3fa 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -205,11 +205,13 @@ crypto_libbitcoin_crypto_a_SOURCES = \
   crypto/sha1.cpp \
   crypto/sha256.cpp \
   crypto/sha512.cpp \
+  crypto/hmac_sha256.cpp \
   crypto/hmac_sha512.cpp \
   crypto/ripemd160.cpp \
   crypto/common.h \
   crypto/sha256.h \
   crypto/sha512.h \
+  crypto/hmac_sha256.h \
   crypto/hmac_sha512.h \
   crypto/sha1.h \
   crypto/ripemd160.h
diff --git a/src/crypto/hmac_sha256.cpp b/src/crypto/hmac_sha256.cpp
new file mode 100644
index 0000000000..435896538b
--- /dev/null
+++ b/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);
+}
diff --git a/src/crypto/hmac_sha256.h b/src/crypto/hmac_sha256.h
new file mode 100644
index 0000000000..4ceac70944
--- /dev/null
+++ b/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
diff --git a/src/test/crypto_tests.cpp b/src/test/crypto_tests.cpp
index b3783133d5..466b38fca9 100644
--- a/src/test/crypto_tests.cpp
+++ b/src/test/crypto_tests.cpp
@@ -6,6 +6,7 @@
 #include "crypto/sha1.h"
 #include "crypto/sha256.h"
 #include "crypto/sha512.h"
+#include "crypto/hmac_sha256.h"
 #include "crypto/hmac_sha512.h"
 #include "random.h"
 #include "utilstrencodings.h"
@@ -50,6 +51,11 @@ void TestSHA256(const std::string &in, const std::string &hexout) { TestVector(C
 void TestSHA512(const std::string &in, const std::string &hexout) { TestVector(CSHA512(), in, ParseHex(hexout));}
 void TestRIPEMD160(const std::string &in, const std::string &hexout) { TestVector(CRIPEMD160(), in, ParseHex(hexout));}
 
+void TestHMACSHA256(const std::string &hexkey, const std::string &hexin, const std::string &hexout) {
+    std::vector<unsigned char> key = ParseHex(hexkey);
+    TestVector(CHMAC_SHA256(&key[0], key.size()), ParseHex(hexin), ParseHex(hexout));
+}
+
 void TestHMACSHA512(const std::string &hexkey, const std::string &hexin, const std::string &hexout) {
     std::vector<unsigned char> key = ParseHex(hexkey);
     TestVector(CHMAC_SHA512(&key[0], key.size()), ParseHex(hexin), ParseHex(hexout));
@@ -160,6 +166,43 @@ BOOST_AUTO_TEST_CASE(sha512_testvectors) {
                "37de8c3ef5459d76a52cedc02dc499a3c9ed9dedbfb3281afd9653b8a112fafc");
 }
 
+BOOST_AUTO_TEST_CASE(hmac_sha256_testvectors) {
+    // test cases 1, 2, 3, 4, 6 and 7 of RFC 4231
+    TestHMACSHA256("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b",
+                   "4869205468657265",
+                   "b0344c61d8db38535ca8afceaf0bf12b881dc200c9833da726e9376c2e32cff7");
+    TestHMACSHA256("4a656665",
+                   "7768617420646f2079612077616e7420666f72206e6f7468696e673f",
+                   "5bdcc146bf60754e6a042426089575c75a003f089d2739839dec58b964ec3843");
+    TestHMACSHA256("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+                   "dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd"
+                   "dddddddddddddddddddddddddddddddddddd",
+                   "773ea91e36800e46854db8ebd09181a72959098b3ef8c122d9635514ced565fe");
+    TestHMACSHA256("0102030405060708090a0b0c0d0e0f10111213141516171819",
+                   "cdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcd"
+                   "cdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcd",
+                   "82558a389a443c0ea4cc819899f2083a85f0faa3e578f8077a2e3ff46729665b");
+    TestHMACSHA256("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaa",
+                   "54657374205573696e67204c6172676572205468616e20426c6f636b2d53697a"
+                   "65204b6579202d2048617368204b6579204669727374",
+                   "60e431591ee0b67f0d8a26aacbf5b77f8e0bc6213728c5140546040f0ee37f54");
+    TestHMACSHA256("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+                   "aaaaaa",
+                   "5468697320697320612074657374207573696e672061206c6172676572207468"
+                   "616e20626c6f636b2d73697a65206b657920616e642061206c61726765722074"
+                   "68616e20626c6f636b2d73697a6520646174612e20546865206b6579206e6565"
+                   "647320746f20626520686173686564206265666f7265206265696e6720757365"
+                   "642062792074686520484d414320616c676f726974686d2e",
+                   "9b09ffa71b942fcb27635fbcd5b0e944bfdc63644f0713938a7f51535c3a35e2");
+}
+
 BOOST_AUTO_TEST_CASE(hmac_sha512_testvectors) {
     // test cases 1, 2, 3, 4, 6 and 7 of RFC 4231
     TestHMACSHA512("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b",