First Commit

externals/cryptopp/pssr.cpp

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+// pssr.cpp - originally written and placed in the public domain by Wei Dai
+
+#include "pch.h"
+#include "pssr.h"
+#include "emsa2.h"
+#include "ripemd.h"
+#include "whrlpool.h"
+#include "misc.h"
+
+#include <functional>
+
+NAMESPACE_BEGIN(CryptoPP)
+
+template<> const byte EMSA2HashId<RIPEMD160>::id = 0x31;
+template<> const byte EMSA2HashId<RIPEMD128>::id = 0x32;
+template<> const byte EMSA2HashId<Whirlpool>::id = 0x37;
+
+#ifndef CRYPTOPP_IMPORTS
+
+size_t PSSR_MEM_Base::MinRepresentativeBitLength(size_t hashIdentifierLength, size_t digestLength) const
+{
+	size_t saltLen = SaltLen(digestLength);
+	size_t minPadLen = MinPadLen(digestLength);
+	return 9 + 8*(minPadLen + saltLen + digestLength + hashIdentifierLength);
+}
+
+size_t PSSR_MEM_Base::MaxRecoverableLength(size_t representativeBitLength, size_t hashIdentifierLength, size_t digestLength) const
+{
+	if (AllowRecovery())
+		return SaturatingSubtract(representativeBitLength, MinRepresentativeBitLength(hashIdentifierLength, digestLength)) / 8;
+	return 0;
+}
+
+bool PSSR_MEM_Base::IsProbabilistic() const
+{
+	return SaltLen(1) > 0;
+}
+
+bool PSSR_MEM_Base::AllowNonrecoverablePart() const
+{
+	return true;
+}
+
+bool PSSR_MEM_Base::RecoverablePartFirst() const
+{
+	return false;
+}
+
+void PSSR_MEM_Base::ComputeMessageRepresentative(RandomNumberGenerator &rng,
+	const byte *recoverableMessage, size_t recoverableMessageLength,
+	HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
+	byte *representative, size_t representativeBitLength) const
+{
+	CRYPTOPP_UNUSED(rng), CRYPTOPP_UNUSED(recoverableMessage), CRYPTOPP_UNUSED(recoverableMessageLength);
+	CRYPTOPP_UNUSED(messageEmpty), CRYPTOPP_UNUSED(hashIdentifier);
+	CRYPTOPP_ASSERT(representativeBitLength >= MinRepresentativeBitLength(hashIdentifier.second, hash.DigestSize()));
+
+	const size_t u = hashIdentifier.second + 1;
+	const size_t representativeByteLength = BitsToBytes(representativeBitLength);
+	const size_t digestSize = hash.DigestSize();
+	const size_t saltSize = SaltLen(digestSize);
+	byte *const h = representative + representativeByteLength - u - digestSize;
+
+	SecByteBlock digest(digestSize), salt(saltSize);
+	hash.Final(digest);
+	rng.GenerateBlock(salt, saltSize);
+
+	// compute H = hash of M'
+	byte c[8];
+	PutWord(false, BIG_ENDIAN_ORDER, c, (word32)SafeRightShift<29>(recoverableMessageLength));
+	PutWord(false, BIG_ENDIAN_ORDER, c+4, word32(recoverableMessageLength << 3));
+	hash.Update(c, 8);
+	hash.Update(recoverableMessage, recoverableMessageLength);
+	hash.Update(digest, digestSize);
+	hash.Update(salt, saltSize);
+	hash.Final(h);
+
+	// compute representative
+	GetMGF().GenerateAndMask(hash, representative, representativeByteLength - u - digestSize, h, digestSize, false);
+	byte *xorStart = representative + representativeByteLength - u - digestSize - salt.size() - recoverableMessageLength - 1;
+	xorStart[0] ^= 1;
+	if (recoverableMessage && recoverableMessageLength)
+		xorbuf(xorStart + 1, recoverableMessage, recoverableMessageLength);
+	xorbuf(xorStart + 1 + recoverableMessageLength, salt, salt.size());
+	if (hashIdentifier.first && hashIdentifier.second)
+	{
+		std::memcpy(representative + representativeByteLength - u, hashIdentifier.first, hashIdentifier.second);
+		representative[representativeByteLength - 1] = 0xcc;
+	}
+	else
+	{
+		representative[representativeByteLength - 1] = 0xbc;
+	}
+	if (representativeBitLength % 8 != 0)
+		representative[0] = (byte)Crop(representative[0], representativeBitLength % 8);
+}
+
+DecodingResult PSSR_MEM_Base::RecoverMessageFromRepresentative(
+	HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
+	byte *representative, size_t representativeBitLength,
+	byte *recoverableMessage) const
+{
+	CRYPTOPP_UNUSED(recoverableMessage), CRYPTOPP_UNUSED(messageEmpty), CRYPTOPP_UNUSED(hashIdentifier);
+	CRYPTOPP_ASSERT(representativeBitLength >= MinRepresentativeBitLength(hashIdentifier.second, hash.DigestSize()));
+
+	const size_t u = hashIdentifier.second + 1;
+	const size_t representativeByteLength = BitsToBytes(representativeBitLength);
+	const size_t digestSize = hash.DigestSize();
+	const size_t saltSize = SaltLen(digestSize);
+	const byte *const h = representative + representativeByteLength - u - digestSize;
+
+	SecByteBlock digest(digestSize);
+	hash.Final(digest);
+
+	DecodingResult result(0);
+	bool &valid = result.isValidCoding;
+	size_t &recoverableMessageLength = result.messageLength;
+
+	valid = (representative[representativeByteLength - 1] == (hashIdentifier.second ? 0xcc : 0xbc)) && valid;
+
+	if (hashIdentifier.first && hashIdentifier.second)
+		valid = VerifyBufsEqual(representative + representativeByteLength - u, hashIdentifier.first, hashIdentifier.second) && valid;
+
+	GetMGF().GenerateAndMask(hash, representative, representativeByteLength - u - digestSize, h, digestSize);
+	if (representativeBitLength % 8 != 0)
+		representative[0] = (byte)Crop(representative[0], representativeBitLength % 8);
+
+	// extract salt and recoverableMessage from DB = 00 ... || 01 || M || salt
+	byte *salt = representative + representativeByteLength - u - digestSize - saltSize;
+	byte *M = FindIfNot(representative, salt-1, byte(0));
+	recoverableMessageLength = salt-M-1;
+	if (*M == 0x01 &&
+	   (size_t)(M - representative - (representativeBitLength % 8 != 0)) >= MinPadLen(digestSize) &&
+	   recoverableMessageLength <= MaxRecoverableLength(representativeBitLength, hashIdentifier.second, digestSize))
+	{
+		if (recoverableMessage)
+			std::memcpy(recoverableMessage, M+1, recoverableMessageLength);
+	}
+	else
+	{
+		recoverableMessageLength = 0;
+		valid = false;
+	}
+
+	// verify H = hash of M'
+	byte c[8];
+	PutWord(false, BIG_ENDIAN_ORDER, c, (word32)SafeRightShift<29>(recoverableMessageLength));
+	PutWord(false, BIG_ENDIAN_ORDER, c+4, word32(recoverableMessageLength << 3));
+	hash.Update(c, 8);
+	hash.Update(recoverableMessage, recoverableMessageLength);
+	hash.Update(digest, digestSize);
+	hash.Update(salt, saltSize);
+	valid = hash.Verify(h) && valid;
+
+	if (!AllowRecovery() && valid && recoverableMessageLength != 0)
+		{throw NotImplemented("PSSR_MEM: message recovery disabled");}
+
+	return result;
+}
+
+#endif
+
+NAMESPACE_END