diff --git a/hkdf.h b/hkdf.h
new file mode 100644
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--- /dev/null
+++ b/hkdf.h
@@ -0,0 +1,87 @@
+// hkdf.h - written and placed in public domain by Jeffrey Walton. Copyright assigned to Crypto++ project
+
+#ifndef CRYPTOPP_HASH_KEY_DERIVATION_FUNCTION_H
+#define CRYPTOPP_HASH_KEY_DERIVATION_FUNCTION_H
+
+#include "cryptlib.h"
+#include "hmac.h"
+#include "hrtimer.h"
+#include "secblock.h"
+
+#include <cstring>
+
+NAMESPACE_BEGIN(CryptoPP)
+
+//! abstract base class for key derivation function
+class KeyDerivationFunction
+{
+public:
+	virtual size_t MaxDerivedKeyLength() const =0;
+	virtual bool UsesContext() const =0;
+	//! derive key from secret
+	virtual unsigned int DeriveKey(byte *derived, size_t derivedLen, const byte *secret, size_t secretLen, const byte *salt, size_t saltLen, const byte* context=NULL, size_t contextLen=0) const =0;
+	
+	// If salt is missing, then use the NULL vector. The length depends on the Hash function.
+	static const byte s_NullVector[64];
+};
+
+const byte KeyDerivationFunction::s_NullVector[64] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
+
+//! HKDF from RFC 5869, T should be a HashTransformation class
+template <class T>
+class CRYPTOPP_DLL HKDF : public KeyDerivationFunction
+{
+public:
+	size_t MaxDerivedKeyLength() const {return static_cast<size_t>(T::DIGESTSIZE) * 255;}
+	bool UsesContext() const {return true;}
+	unsigned int DeriveKey(byte *derived, size_t derivedLen, const byte *secret, size_t secretLen, const byte *salt, size_t saltLen, const byte* context, size_t contextLen) const;
+};
+
+template <class T>
+unsigned int HKDF<T>::DeriveKey(byte *derived, size_t derivedLen, const byte *secret, size_t secretLen, const byte *salt, size_t saltLen, const byte* context, size_t contextLen) const
+{
+	static const size_t DIGEST_SIZE = static_cast<size_t>(T::DIGESTSIZE);
+	CRYPTOPP_COMPILE_ASSERT(DIGEST_SIZE <= COUNTOF(s_NullVector));
+	const unsigned int req = static_cast<unsigned int>(derivedLen);
+	
+	assert(secret && secretLen);
+	assert(derived && derivedLen);
+	assert(derivedLen <= MaxDerivedKeyLength());
+
+	if(derivedLen > MaxDerivedKeyLength())
+		throw InvalidArgument("HKDF: derivedLen must be less than or equal to MaxDerivedKeyLength");
+
+	HMAC<T> hmac;
+	FixedSizeSecBlock<byte, DIGEST_SIZE> prk, buffer;
+
+	// Extract
+	const byte* key = (salt ? salt : s_NullVector);
+	const size_t klen = (salt ? saltLen : DIGEST_SIZE);
+
+	hmac.SetKey(key, klen);
+	hmac.CalculateDigest(prk, secret, secretLen);
+
+	// Expand
+	hmac.SetKey(prk.data(), prk.size());
+	byte block = 0;
+
+	while (derivedLen > 0)
+	{
+		if(block++) {hmac.Update(buffer, buffer.size());}
+		if(context && contextLen) {hmac.Update(context, contextLen);}
+		hmac.CalculateDigest(buffer, &block, 1);
+
+		size_t segmentLen = STDMIN(derivedLen, DIGEST_SIZE);
+		std::memcpy(derived, buffer, segmentLen);
+
+		derived += segmentLen;
+		derivedLen -= segmentLen;
+	}
+
+	return req;
+}
+
+NAMESPACE_END
+
+#endif // CRYPTOPP_HASH_KEY_DERIVATION_FUNCTION_H
+