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-rw-r--r--modules/cipher/idea/idea.cpp172
1 files changed, 172 insertions, 0 deletions
diff --git a/modules/cipher/idea/idea.cpp b/modules/cipher/idea/idea.cpp
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+/*************************************************
+* IDEA Source File *
+* (C) 1999-2007 Jack Lloyd *
+*************************************************/
+
+#include <botan/idea.h>
+#include <botan/loadstor.h>
+
+namespace Botan {
+
+namespace {
+
+/*************************************************
+* Multiplication modulo 65537 *
+*************************************************/
+inline u16bit mul(u16bit x, u16bit y)
+ {
+ if(x && y)
+ {
+ u32bit T = static_cast<u32bit>(x) * y;
+ x = static_cast<u16bit>(T >> 16);
+ y = static_cast<u16bit>(T & 0xFFFF);
+ return static_cast<u16bit>(y - x + ((y < x) ? 1 : 0));
+ }
+ else
+ return static_cast<u16bit>(1 - x - y);
+ }
+
+/*************************************************
+* Find multiplicative inverses modulo 65537 *
+*************************************************/
+u16bit mul_inv(u16bit x)
+ {
+ if(x <= 1)
+ return x;
+
+ u16bit t0 = static_cast<u16bit>(65537 / x), t1 = 1;
+ u16bit y = static_cast<u16bit>(65537 % x);
+
+ while(y != 1)
+ {
+ u16bit q = x / y;
+ x %= y;
+ t1 += q * t0;
+
+ if(x == 1)
+ return t1;
+
+ q = y / x;
+ y %= x;
+ t0 += q * t1;
+ }
+ return (1 - t0);
+ }
+
+}
+
+/*************************************************
+* IDEA Encryption *
+*************************************************/
+void IDEA::enc(const byte in[], byte out[]) const
+ {
+ u16bit X1 = load_be<u16bit>(in, 0);
+ u16bit X2 = load_be<u16bit>(in, 1);
+ u16bit X3 = load_be<u16bit>(in, 2);
+ u16bit X4 = load_be<u16bit>(in, 3);
+
+ for(u32bit j = 0; j != 8; ++j)
+ {
+ X1 = mul(X1, EK[6*j+0]);
+ X2 += EK[6*j+1];
+ X3 += EK[6*j+2];
+ X4 = mul(X4, EK[6*j+3]);
+
+ u16bit T0 = X3;
+ X3 = mul(X3 ^ X1, EK[6*j+4]);
+
+ u16bit T1 = X2;
+ X2 = mul((X2 ^ X4) + X3, EK[6*j+5]);
+ X3 += X2;
+
+ X1 ^= X2;
+ X4 ^= X3;
+ X2 ^= T0;
+ X3 ^= T1;
+ }
+
+ X1 = mul(X1, EK[48]);
+ X2 += EK[50];
+ X3 += EK[49];
+ X4 = 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<u16bit>(in, 0);
+ u16bit X2 = load_be<u16bit>(in, 1);
+ u16bit X3 = load_be<u16bit>(in, 2);
+ u16bit X4 = load_be<u16bit>(in, 3);
+
+ for(u32bit j = 0; j != 8; ++j)
+ {
+ X1 = mul(X1, DK[6*j+0]);
+ X2 += DK[6*j+1];
+ X3 += DK[6*j+2];
+ X4 = mul(X4, DK[6*j+3]);
+
+ u16bit T0 = X3;
+ X3 = mul(X3 ^ X1, DK[6*j+4]);
+
+ u16bit T1 = X2;
+ X2 = mul((X2 ^ X4) + X3, DK[6*j+5]);
+ X3 += X2;
+
+ X1 ^= X2;
+ X4 ^= X3;
+ X2 ^= T0;
+ X3 ^= T1;
+ }
+
+ X1 = mul(X1, DK[48]);
+ X2 += DK[50];
+ X3 += DK[49];
+ X4 = mul(X4, DK[51]);
+
+ store_be(out, X1, X3, X2, X4);
+ }
+
+/*************************************************
+* IDEA Key Schedule *
+*************************************************/
+void IDEA::key(const byte key[], u32bit)
+ {
+ for(u32bit j = 0; j != 8; ++j)
+ EK[j] = load_be<u16bit>(key, j);
+
+ for(u32bit j = 1, k = 8, offset = 0; k != 52; j %= 8, ++j, ++k)
+ {
+ EK[j+7+offset] = static_cast<u16bit>((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]);
+ }
+
+}