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#pragma once
// https://www.schneier.com/academic/archives/1994/09/description_of_a_new.html
#include "blowfish_init.hpp"
#include <algorithm>
class Blowfish {
public:
struct Block {
constexpr Block(uint64_t x) {
L = x >> 32;
R = x & 0xffffffff;
}
constexpr Block(uint32_t l, uint32_t r) : L(l), R(r) {}
constexpr operator uint64_t() const {
return (static_cast<uint64_t>(L) << 32) + R;
}
uint32_t L;
uint32_t R;
};
constexpr Blowfish(const uint8_t key[], size_t keylen) {
for (size_t i = 0; i < BOXES; ++i) {
for (size_t j = 0; j < ENTRIES; ++j) {
S[i][j] = S_INIT[i][j];
}
}
//
size_t k = 0;
for (size_t i = 0; i < SUBKEYS; ++i) {
uint32_t qk = 0;
for (size_t j = 0; j < 4; ++j) {
qk = (qk << 8) | key[k];
++k;
if (k >= keylen) {
k = 0;
}
}
P[i] = P_INIT[i] ^ qk;
}
Block x(0, 0);
for (size_t i = 0; i < SUBKEYS; i += 2) {
x = encrypt(x);
P[i] = x.L;
P[i + 1] = x.R;
}
for (size_t i = 0; i < BOXES; ++i) {
for (size_t j = 0; j < ENTRIES; j += 2) {
x = encrypt(x);
S[i][j] = x.L;
S[i][j + 1] = x.R;
}
}
}
constexpr Block encrypt(const Block &x) const {
Block y(x);
for (size_t i = 0; i < ROUNDS; ++i) {
y.L = y.L ^ P[i];
y.R = F(y.L) ^ y.R;
std::swap(y.L, y.R);
}
std::swap(y.L, y.R);
y.R = y.R ^ P[16];
y.L = y.L ^ P[17];
return y;
}
constexpr Block decrypt(const Block &x) const {
Block y(x);
for (size_t i = ROUNDS + 1; i > 1; --i) {
y.L = y.L ^ P[i];
y.R = F(y.L) ^ y.R;
std::swap(y.L, y.R);
}
std::swap(y.L, y.R);
y.R = y.R ^ P[1];
y.L = y.L ^ P[0];
return y;
}
private:
constexpr uint32_t F(uint32_t x) const {
const uint8_t a = (x >> 24) & 0xff;
const uint8_t b = (x >> 16) & 0xff;
const uint8_t c = (x >> 8) & 0xff;
const uint8_t d = x & 0xff;
uint32_t y = S[0][a] + S[1][b];
y = y ^ S[2][c];
y = y + S[3][d];
return y;
}
uint32_t P[SUBKEYS];
uint32_t S[BOXES][ENTRIES];
};
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