選択できるのは25トピックまでです。
トピックは、先頭が英数字で、英数字とダッシュ('-')を使用した35文字以内のものにしてください。
133 行
2.8 KiB
133 行
2.8 KiB
#pragma once
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#include <stdint.h>
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#include <stddef.h>
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#include <algorithm>
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#include <array>
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template<typename word_t>
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size_t lg(word_t v);
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/**
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Sean Eron Anderson
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seander@cs.stanford.edu
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**/
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template<>
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size_t lg<uint32_t>(uint32_t v)
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{
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static const int MultiplyDeBruijnBitPosition[32] =
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{
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0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30,
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8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31
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};
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v |= v >> 1;
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v |= v >> 2;
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v |= v >> 4;
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v |= v >> 8;
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v |= v >> 16;
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return MultiplyDeBruijnBitPosition[(uint32_t)(v * 0x07C4ACDDU) >> 27];
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}
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template<>
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size_t lg<uint64_t>(uint64_t v)
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{
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static const int MultiplyDeBruijnBitPosition[64] =
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{
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0, 58, 1, 59, 47, 53, 2, 60, 39, 48, 27, 54, 33, 42, 3, 61,
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51, 37, 40, 49, 18, 28, 20, 55, 30, 34, 11, 43, 14, 22, 4, 62,
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57, 46, 52, 38, 26, 32, 41, 50, 36, 17, 19, 29, 10, 13, 21, 56,
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45, 25, 31, 35, 16, 9, 12, 44, 24, 15, 8, 23, 7, 6, 5, 63
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};
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v |= v >> 1;
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v |= v >> 2;
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v |= v >> 4;
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v |= v >> 8;
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v |= v >> 16;
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v |= v >> 32;
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return MultiplyDeBruijnBitPosition[(uint64_t)(v * 0x03f6eaf2cd271461) >> 58];
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}
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template<typename word_t = uint32_t, size_t r = 20, size_t b = 128, word_t P = 0xB7E15163, word_t Q = 0x9E3779B9>
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class RC6 {
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static constexpr size_t word_size = 8*sizeof(word_t);
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static word_t r_l(const word_t& w, size_t v) {
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return (w << v) | ( w >> (sizeof(w)-v));
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}
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static word_t r_r(const word_t& w, size_t v) {
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return (w >> v) | ( w << (sizeof(w)-v));
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}
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class RC6_KeySched {
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public:
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static constexpr size_t c = (b+word_size-1)/word_size;
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static constexpr size_t v_3 = std::max(c, 2*r+4);
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static constexpr size_t v = v_3*3;
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private:
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std::array<word_t, 2*r+4> S;
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public:
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RC6_KeySched(std::array<word_t, c> L)
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{
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S[0] = P;
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for(auto it = S.begin()+1; it < S.end(); ++it)
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{
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*it = *(it-1) + Q;
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}
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word_t A = 0;
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word_t B = 0;
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word_t i = 0;
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word_t j = 0;
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for(size_t s = 0; s < v; ++s)
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{
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i = s % (2*r+4);
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j = s % c;
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A = S[i] = r_l( S[i] + A + B, 3 );
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B = L[j] = r_l( L[j] + A + B, (A + B)%(word_size));
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}
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}
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const word_t& operator[](const size_t pos) {
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return S[pos];
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}
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};
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RC6_KeySched S;
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public:
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typedef std::array<word_t, RC6_KeySched::c> key_type;
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typedef std::array<word_t, 4> block_type;
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RC6(const key_type& key)
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: S(key)
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{}
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void encrypt(block_type& plaintext) {
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auto& A = plaintext[0];
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auto& B = plaintext[1];
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auto& C = plaintext[2];
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auto& D = plaintext[3];
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B += S[0];
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D += S[1];
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for(size_t i = 1; i <= r; ++i)
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{
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auto t = r_l( B * ( 2 * B + 1 ), 5);
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auto u = r_l( D * ( 2 * D + 1 ), 5);
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A = r_l((A ^ t), u % word_size) + S[ 2 * i ];
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C = r_l((C ^ u), t % word_size) + S[ 2 * i + 1 ];
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auto tmp = A; A = B; B = C; C = D; D = tmp;
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}
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A += S[2*r+2];
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C += S[2*r+3];
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}
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};
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