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64 lines
1.4 KiB
64 lines
1.4 KiB
// 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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#include "integer.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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current(modn.Square(modn.Square(seed))), |
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maxBits(BitPrecision(n.BitCount())-1), |
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bitsLeft(maxBits) |
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{ |
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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 = byte((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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