64 lines
1.3 KiB
C++
64 lines
1.3 KiB
C++
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// blumshub.cpp - written and placed in the public domain by Wei Dai
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#include "pch.h"
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#include "blumshub.h"
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NAMESPACE_BEGIN(CryptoPP)
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PublicBlumBlumShub::PublicBlumBlumShub(const Integer &n, const Integer &seed)
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: modn(n),
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maxBits(BitPrecision(n.BitCount())-1)
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{
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current = modn.Square(modn.Square(seed));
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bitsLeft = maxBits;
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}
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unsigned int PublicBlumBlumShub::GenerateBit()
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{
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if (bitsLeft==0)
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{
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current = modn.Square(current);
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bitsLeft = maxBits;
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}
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return current.GetBit(--bitsLeft);
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}
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byte PublicBlumBlumShub::GenerateByte()
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{
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byte b=0;
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for (int i=0; i<8; i++)
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b = (b << 1) | PublicBlumBlumShub::GenerateBit();
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return b;
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}
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void PublicBlumBlumShub::GenerateBlock(byte *output, size_t size)
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{
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while (size--)
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*output++ = PublicBlumBlumShub::GenerateByte();
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}
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void PublicBlumBlumShub::ProcessData(byte *outString, const byte *inString, size_t length)
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{
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while (length--)
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*outString++ = *inString++ ^ PublicBlumBlumShub::GenerateByte();
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}
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BlumBlumShub::BlumBlumShub(const Integer &p, const Integer &q, const Integer &seed)
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: PublicBlumBlumShub(p*q, seed),
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p(p), q(q),
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x0(modn.Square(seed))
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{
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}
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void BlumBlumShub::Seek(lword index)
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{
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Integer i(Integer::POSITIVE, index);
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i *= 8;
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Integer e = a_exp_b_mod_c (2, i / maxBits + 1, (p-1)*(q-1));
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current = modn.Exponentiate(x0, e);
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bitsLeft = maxBits - i % maxBits;
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}
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NAMESPACE_END
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