General Purpose library for Freestanding C++ and POSIX systems
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#pragma once
#include <stdint.h>
#include <stddef.h>
#include <algorithm>
#include <array>
template<typename word_t>
size_t lg(word_t v);
/**
Sean Eron Anderson
seander@cs.stanford.edu
**/
template<>
size_t lg<uint32_t>(uint32_t v)
{
static const int MultiplyDeBruijnBitPosition[32] =
{
0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30,
8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31
};
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
return MultiplyDeBruijnBitPosition[(uint32_t)(v * 0x07C4ACDDU) >> 27];
}
template<>
size_t lg<uint64_t>(uint64_t v)
{
static const int MultiplyDeBruijnBitPosition[64] =
{
0, 58, 1, 59, 47, 53, 2, 60, 39, 48, 27, 54, 33, 42, 3, 61,
51, 37, 40, 49, 18, 28, 20, 55, 30, 34, 11, 43, 14, 22, 4, 62,
57, 46, 52, 38, 26, 32, 41, 50, 36, 17, 19, 29, 10, 13, 21, 56,
45, 25, 31, 35, 16, 9, 12, 44, 24, 15, 8, 23, 7, 6, 5, 63
};
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v |= v >> 32;
return MultiplyDeBruijnBitPosition[(uint64_t)(v * 0x03f6eaf2cd271461) >> 58];
}
template<typename word_t = uint32_t, size_t r = 20, size_t b = 128, word_t P = 0xB7E15163, word_t Q = 0x9E3779B9>
class RC6 {
static word_t r_l(const word_t& w, size_t v) {
return (w << v) | ( w >> (sizeof(w)-v));
}
static word_t r_r(const word_t& w, size_t v) {
return (w >> v) | ( w << (sizeof(w)-v));
}
class RC6_KeySched {
public:
static constexpr size_t c = b/sizeof(word_t)/8;
static constexpr size_t v_3 = std::max(c, 2*r+4);
static constexpr size_t v = v_3*3;
private:
std::array<word_t, v_3> S;
public:
RC6_KeySched(std::array<word_t, c> L)
{
S[0] = P;
for(size_t i = 1; i < 2*r+3; ++i)
{
S[i] = S[i - 1] + Q;
}
word_t A = 0;
word_t B = 0;
word_t i = 0;
word_t j = 0;
for(size_t s = 1; s < v; ++s)
{
A = S[i] = r_l( S[i] + A + B, 3 );
B = L[j] = r_l( L[j] + A + B, (A + B)%(8*sizeof(word_t)));
i = (i + 1) % (2*r+4);
j = (j + 1) % c;
}
}
const word_t& operator[](const size_t pos) {
return S[pos];
}
};
RC6_KeySched S;
public:
typedef std::array<word_t, RC6_KeySched::c> key_type;
typedef std::array<word_t, 4> block_type;
RC6(const key_type& key)
: S(key)
{}
void encrypt(block_type& plaintext) {
auto& A = plaintext[0];
auto& B = plaintext[1];
auto& C = plaintext[2];
auto& D = plaintext[3];
B += S[0];
D += S[1];
for(size_t i = 1; i < r; ++i)
{
auto t = r_l( B * ( 2 * B + 1 ), 5);
auto u = r_l( D * ( 2 * D + 1 ), 5);
A = ((A ^ t) << u%(8*sizeof(word_t))) + S[2*i];
C = ((C ^ u) << t%(8*sizeof(word_t))) + S[2*i+1];
std::rotate(plaintext.begin(), plaintext.begin()+1, plaintext.end());
}
A += S[2*r+3];
C += S[2*r+2];
}
};