Add HKDF HMAC_SHA256 L=32 implementations

1 files changed, 25 insertions, 0 deletions

diff --git a/src/crypto/hkdf_sha256_32.h b/src/crypto/hkdf_sha256_32.h
new file mode 100644
index 0000000000..fa1e42aec1
--- /dev/null
+++ b/src/crypto/hkdf_sha256_32.h
@@ -0,0 +1,25 @@
+// Copyright (c) 2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_HKDF_SHA256_32_H
+#define BITCOIN_CRYPTO_HKDF_SHA256_32_H
+
+#include <crypto/hmac_sha256.h>
+
+#include <stdint.h>
+#include <stdlib.h>
+
+/** A rfc5869 HKDF implementation with HMAC_SHA256 and fixed key output length of 32 bytes (L=32) */
+class CHKDF_HMAC_SHA256_L32
+{
+private:
+    unsigned char m_prk[32];
+    static const size_t OUTPUT_SIZE = 32;
+
+public:
+    CHKDF_HMAC_SHA256_L32(const unsigned char* ikm, size_t ikmlen, const std::string& salt);
+    void Expand32(const std::string& info, unsigned char hash[OUTPUT_SIZE]);
+};
+
+#endif // BITCOIN_CRYPTO_HKDF_SHA256_32_H