/************************************************* * RC5 Source File * * (C) 1999-2008 The Botan Project * *************************************************/ #include #include #include #include #include namespace Botan { /************************************************* * RC5 Encryption * *************************************************/ void RC5::enc(const byte in[], byte out[]) const { u32bit A = load_le(in, 0), B = load_le(in, 1); A += S[0]; B += S[1]; for(u32bit j = 0; j != ROUNDS; j += 4) { A = rotate_left(A ^ B, B % 32) + S[2*j+2]; B = rotate_left(B ^ A, A % 32) + S[2*j+3]; A = rotate_left(A ^ B, B % 32) + S[2*j+4]; B = rotate_left(B ^ A, A % 32) + S[2*j+5]; A = rotate_left(A ^ B, B % 32) + S[2*j+6]; B = rotate_left(B ^ A, A % 32) + S[2*j+7]; A = rotate_left(A ^ B, B % 32) + S[2*j+8]; B = rotate_left(B ^ A, A % 32) + S[2*j+9]; } store_le(out, A, B); } /************************************************* * RC5 Decryption * *************************************************/ void RC5::dec(const byte in[], byte out[]) const { u32bit A = load_le(in, 0), B = load_le(in, 1); for(u32bit j = ROUNDS; j != 0; j -= 4) { B = rotate_right(B - S[2*j+1], A % 32) ^ A; A = rotate_right(A - S[2*j ], B % 32) ^ B; B = rotate_right(B - S[2*j-1], A % 32) ^ A; A = rotate_right(A - S[2*j-2], B % 32) ^ B; B = rotate_right(B - S[2*j-3], A % 32) ^ A; A = rotate_right(A - S[2*j-4], B % 32) ^ B; B = rotate_right(B - S[2*j-5], A % 32) ^ A; A = rotate_right(A - S[2*j-6], B % 32) ^ B; } B -= S[1]; A -= S[0]; store_le(out, A, B); } /************************************************* * RC5 Key Schedule * *************************************************/ void RC5::key(const byte key[], u32bit length) { const u32bit WORD_KEYLENGTH = (((length - 1) / 4) + 1), MIX_ROUNDS = 3*std::max(WORD_KEYLENGTH, S.size()); S[0] = 0xB7E15163; for(u32bit j = 1; j != S.size(); ++j) S[j] = S[j-1] + 0x9E3779B9; SecureBuffer K; for(s32bit j = length-1; j >= 0; --j) K[j/4] = (K[j/4] << 8) + key[j]; for(u32bit j = 0, A = 0, B = 0; j != MIX_ROUNDS; ++j) { A = rotate_left(S[j % S.size()] + A + B, 3); B = rotate_left(K[j % WORD_KEYLENGTH] + A + B, (A + B) % 32); S[j % S.size()] = A; K[j % WORD_KEYLENGTH] = B; } } /************************************************* * Return the name of this type * *************************************************/ std::string RC5::name() const { return "RC5(" + to_string(ROUNDS) + ")"; } /************************************************* * RC5 Constructor * *************************************************/ RC5::RC5(u32bit r) : BlockCipher(8, 1, 32), ROUNDS(r) { if(ROUNDS < 8 || ROUNDS > 32 || (ROUNDS % 4 != 0)) throw Invalid_Argument(name() + ": Invalid number of rounds"); S.create(2*ROUNDS + 2); } }