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