Initial commit

1 files changed, 103 insertions, 0 deletions

diff --git a/blowfish.hpp b/blowfish.hpp
new file mode 100644
index 0000000..e0468cd
--- /dev/null
+++ b/blowfish.hpp
@@ -0,0 +1,103 @@
+#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];
+};