/************************************************* * IDEA Source File * * (C) 1999-2007 The Botan Project * *************************************************/ #include #include namespace Botan { namespace { /************************************************* * Multiplication modulo 65537 * *************************************************/ inline void mul(u16bit& a, u16bit b) { if(a && b) { u32bit temp = static_cast(a) * b; a = static_cast(temp >> 16); b = static_cast(temp & 0xFFFF); a = static_cast(b - a + ((b < a) ? 1 : 0)); } else a = static_cast(1 - a - b); } } /************************************************* * IDEA Encryption * *************************************************/ void IDEA::enc(const byte in[], byte out[]) const { u16bit X1 = load_be(in, 0); u16bit X2 = load_be(in, 1); u16bit X3 = load_be(in, 2); u16bit X4 = load_be(in, 3); for(u32bit j = 0; j != 8; ++j) { mul(X1, EK[6*j+0]); X2 += EK[6*j+1]; X3 += EK[6*j+2]; mul(X4, EK[6*j+3]); u16bit T0 = X3; X3 ^= X1; mul(X3, EK[6*j+4]); u16bit T1 = X2; X2 = static_cast((X2 ^ X4) + X3); mul(X2, EK[6*j+5]); X3 += X2; X1 ^= X2; X4 ^= X3; X2 ^= T0; X3 ^= T1; } mul(X1, EK[48]); X2 += EK[50]; X3 += EK[49]; mul(X4, EK[51]); store_be(out, X1, X3, X2, X4); } /************************************************* * IDEA Decryption * *************************************************/ void IDEA::dec(const byte in[], byte out[]) const { u16bit X1 = load_be(in, 0); u16bit X2 = load_be(in, 1); u16bit X3 = load_be(in, 2); u16bit X4 = load_be(in, 3); for(u32bit j = 0; j != 8; ++j) { mul(X1, DK[6*j+0]); X2 += DK[6*j+1]; X3 += DK[6*j+2]; mul(X4, DK[6*j+3]); u16bit T0 = X3; X3 ^= X1; mul(X3, DK[6*j+4]); u16bit T1 = X2; X2 = static_cast((X2 ^ X4) + X3); mul(X2, DK[6*j+5]); X3 += X2; X1 ^= X2; X4 ^= X3; X2 ^= T0; X3 ^= T1; } mul(X1, DK[48]); X2 += DK[50]; X3 += DK[49]; mul(X4, DK[51]); store_be(out, X1, X3, X2, X4); } /************************************************* * Find multiplicative inverses modulo 65537 * *************************************************/ u16bit IDEA::mul_inv(u16bit x) { if(x <= 1) return x; u16bit t0 = static_cast(65537 / x), t1 = 1; u16bit y = static_cast(65537 % x); while(y != 1) { u16bit q = static_cast(x / y); x %= y; t1 += static_cast(q * t0); if(x == 1) return t1; q = static_cast(y / x); y %= x; t0 += static_cast(q * t1); } return static_cast(1 - t0); } /************************************************* * IDEA Key Schedule * *************************************************/ void IDEA::key(const byte key[], u32bit) { for(u32bit j = 0; j != 8; ++j) EK[j] = load_be(key, j); for(u32bit j = 1, k = 8, offset = 0; k != 52; j %= 8, ++j, ++k) { EK[j+7+offset] = static_cast((EK[(j % 8) + offset] << 9) | (EK[((j+1) % 8) + offset] >> 7)); offset += (j == 8) ? 8 : 0; } DK[51] = mul_inv(EK[3]); DK[50] = -EK[2]; DK[49] = -EK[1]; DK[48] = mul_inv(EK[0]); for(u32bit j = 1, k = 4, counter = 47; j != 8; ++j, k += 6) { DK[counter--] = EK[k+1]; DK[counter--] = EK[k]; DK[counter--] = mul_inv(EK[k+5]); DK[counter--] = -EK[k+3]; DK[counter--] = -EK[k+4]; DK[counter--] = mul_inv(EK[k+2]); } DK[5] = EK[47]; DK[4] = EK[46]; DK[3] = mul_inv(EK[51]); DK[2] = -EK[50]; DK[1] = -EK[49]; DK[0] = mul_inv(EK[48]); } }