Initial revision

1 files changed, 114 insertions, 0 deletions

diff --git a/dsa.cpp b/dsa.cpp
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index 00000000..4bdbae61
--- /dev/null
+++ b/dsa.cpp
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+// dsa.cpp - written and placed in the public domain by Wei Dai
+
+#include "pch.h"
+#include "dsa.h"
+#include "nbtheory.h"
+
+NAMESPACE_BEGIN(CryptoPP)
+
+unsigned int DSAConvertSignatureFormat(byte *buffer, unsigned int bufferSize, DSASignatureFormat toFormat, const byte *signature, unsigned int signatureLen, DSASignatureFormat fromFormat)
+{
+	Integer r, s;
+	StringStore store(signature, signatureLen);
+	ArraySink sink(buffer, bufferSize);
+
+	switch (fromFormat)
+	{
+	case DSA_P1363:
+		r.Decode(store, signatureLen/2);
+		s.Decode(store, signatureLen/2);
+		break;
+	case DSA_DER:
+	{
+		BERSequenceDecoder seq(store);
+		r.BERDecode(seq);
+		s.BERDecode(seq);
+		seq.MessageEnd();
+		break;
+	}
+	case DSA_OPENPGP:
+		r.OpenPGPDecode(store);
+		s.OpenPGPDecode(store);
+		break;
+	}
+
+	switch (toFormat)
+	{
+	case DSA_P1363:
+		r.Encode(sink, bufferSize/2);
+		s.Encode(sink, bufferSize/2);
+		break;
+	case DSA_DER:
+	{
+		DERSequenceEncoder seq(sink);
+		r.DEREncode(seq);
+		s.DEREncode(seq);
+		seq.MessageEnd();
+		break;
+	}
+	case DSA_OPENPGP:
+		r.OpenPGPEncode(sink);
+		s.OpenPGPEncode(sink);
+		break;
+	}
+
+	return sink.TotalPutLength();
+}
+
+bool DSA::GeneratePrimes(const byte *seedIn, unsigned int g, int &counter,
+						  Integer &p, unsigned int L, Integer &q, bool useInputCounterValue)
+{
+	assert(g%8 == 0);
+
+	SHA sha;
+	SecByteBlock seed(seedIn, g/8);
+	SecByteBlock U(SHA::DIGESTSIZE);
+	SecByteBlock temp(SHA::DIGESTSIZE);
+	SecByteBlock W(((L-1)/160+1) * SHA::DIGESTSIZE);
+	const int n = (L-1) / 160;
+	const int b = (L-1) % 160;
+	Integer X;
+
+	sha.CalculateDigest(U, seed, g/8);
+
+	for (int i=g/8-1, carry=true; i>=0 && carry; i--)
+		carry=!++seed[i];
+
+	sha.CalculateDigest(temp, seed, g/8);
+	xorbuf(U, temp, SHA::DIGESTSIZE);
+
+	U[0] |= 0x80;
+	U[SHA::DIGESTSIZE-1] |= 1;
+	q.Decode(U, SHA::DIGESTSIZE);
+
+	if (!IsPrime(q))
+		return false;
+
+	int counterEnd = useInputCounterValue ? counter+1 : 4096;
+
+	for (int c = 0; c < counterEnd; c++)
+	{
+		for (int k=0; k<=n; k++)
+		{
+			for (int i=g/8-1, carry=true; i>=0 && carry; i--)
+				carry=!++seed[i];
+			if (!useInputCounterValue || c == counter)
+				sha.CalculateDigest(W+(n-k)*SHA::DIGESTSIZE, seed, g/8);
+		}
+		if (!useInputCounterValue || c == counter)
+		{
+			W[SHA::DIGESTSIZE - 1 - b/8] |= 0x80;
+			X.Decode(W + SHA::DIGESTSIZE - 1 - b/8, L/8);
+			p = X-((X % (2*q))-1);
+
+			if (p.GetBit(L-1) && IsPrime(p))
+			{
+				counter = c;
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
+NAMESPACE_END