Initial revision

1 files changed, 46 insertions, 0 deletions

diff --git a/trunhash.h b/trunhash.h
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+++ b/trunhash.h
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+#ifndef CRYPTOPP_TRUNHASH_H
+#define CRYPTOPP_TRUNHASH_H
+
+#include "cryptlib.h"
+
+NAMESPACE_BEGIN(CryptoPP)
+
+class NullHash : public HashTransformation
+{
+public:
+	void Update(const byte *input, unsigned int length) {}
+	unsigned int DigestSize() const {return 0;}
+	void TruncatedFinal(byte *digest, unsigned int digestSize) {}
+	bool TruncatedVerify(const byte *digest, unsigned int digestLength) {return true;}
+};
+
+//! construct new HashModule with smaller DigestSize() from existing one
+template <class T>
+class TruncatedHashTemplate : public HashTransformation
+{
+public:
+	TruncatedHashTemplate(T hm, unsigned int digestSize)
+		: m_hm(hm), m_digestSize(digestSize) {}
+	TruncatedHashTemplate(const byte *key, unsigned int keyLength, unsigned int digestSize)
+		: m_hm(key, keyLength), m_digestSize(digestSize) {}
+	TruncatedHashTemplate(unsigned int digestSize)
+		: m_digestSize(digestSize) {}
+
+	void Update(const byte *input, unsigned int length)
+		{m_hm.Update(input, length);}
+	unsigned int DigestSize() const {return m_digestSize;}
+	void TruncatedFinal(byte *digest, unsigned int digestSize)
+		{m_hm.TruncatedFinal(digest, digestSize);}
+	bool TruncatedVerify(const byte *digest, unsigned int digestLength)
+		{return m_hm.TruncatedVerify(digest, digestLength);}
+
+private:
+	T m_hm;
+	unsigned int m_digestSize;
+};
+
+typedef TruncatedHashTemplate<HashTransformation &> TruncatedHashModule;
+
+NAMESPACE_END
+
+#endif