Add HKDF HMAC_SHA256 L=32 implementations

1 files changed, 21 insertions, 0 deletions

diff --git a/src/crypto/hkdf_sha256_32.cpp b/src/crypto/hkdf_sha256_32.cpp
new file mode 100644
index 0000000000..9cea5995ec
--- /dev/null
+++ b/src/crypto/hkdf_sha256_32.cpp
@@ -0,0 +1,21 @@
+// 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.
+
+#include <crypto/hkdf_sha256_32.h>
+
+#include <assert.h>
+#include <string.h>
+
+CHKDF_HMAC_SHA256_L32::CHKDF_HMAC_SHA256_L32(const unsigned char* ikm, size_t ikmlen, const std::string& salt)
+{
+    CHMAC_SHA256((const unsigned char*)salt.c_str(), salt.size()).Write(ikm, ikmlen).Finalize(m_prk);
+}
+
+void CHKDF_HMAC_SHA256_L32::Expand32(const std::string& info, unsigned char hash[OUTPUT_SIZE])
+{
+    // expand a 32byte key (single round)
+    assert(info.size() <= 128);
+    static const unsigned char one[1] = {1};
+    CHMAC_SHA256(m_prk, 32).Write((const unsigned char*)info.data(), info.size()).Write(one, 1).Finalize(hash);
+}