/* * Copyright (C) 1995, 1996 Systemics Ltd (http://www.systemics.com/) * All rights reserved. * * This library and applications are FREE FOR COMMERCIAL AND NON-COMMERCIAL USE * as long as the conditions within the COPYRIGHT file are adhered to. * */#include "local.h"#include "idea.h"#define KEYS_PER_ROUND	6#define ROUNDS			8 #define KEYLEN			(KEYS_PER_ROUND*ROUNDS+4)/* *	Multiplication modulo (2**16)+1 */static u_int16_tmul(u_int16_t a, u_int16_t b){	int32_t p;	if (a)	{		if (b)		{			p = a * b;			b = p & 0xFFFF;			a = p >> 16;			return b - a + (b < a);		}		else			return (1 - a);	}	return (1 - b); }/* * Compute inverse of x, modulo (2**16)+1, using Euclidean gcd algorithm */static u_int16_tinv(u_int16_t x){	u_int16_t t0, t1, q, y;	if (x <= 1)	/* Since zero and one are self inverse */		return x;	t1 = 0x10001L / x;	/* Since x >= 2, the result is 16bit */	y = 0x10001L % x;	if (y == 1)		return ((1 - t1) & 0xFFFF);	t0 = 1;	do	{		q = x / y;		x %= y;		t0 += q * t1;		if (x == 1)			return t0;		q = y / x;		y = y % x;		t1 += q * t0;	} while (y != 1);	return (1-t1);}/* *	Encryption and decryption */voididea_crypt(u_int16_t * in, u_int16_t * out, u_int16_t * key){	int i = ROUNDS;	u_int16_t x0, x1, x2, x3, t0, t1;	x0 = *(in++);	x1 = *(in++);	x2 = *(in++);	x3 = *(in);	#ifdef LITTLE_ENDIAN	x0 = SWAP_BYTES(x0);	x1 = SWAP_BYTES(x1);	x2 = SWAP_BYTES(x2);	x3 = SWAP_BYTES(x3);#endif	do {		x0 = mul(x0, *(key++));		x1 += *(key++);		x2 += *(key++);		x3 = mul(x3, *(key++));		t0 = x2;		x2 = mul(x0^x2, *(key++));		t1 = x1;		x1 = mul((x1^x3)+x2, *(key++));		x2 += x1;		x0 ^= x1;		x3 ^= x2;		x1 ^= t0;		x2 ^= t1;	} while (--i);	x0 = mul(x0, *(key++));	t0 = x1;	x1 = x2 + *(key++);	x2 = t0 + *(key++);	x3 = mul(x3, *key);	#ifdef LITTLE_ENDIAN	x0 = SWAP_BYTES(x0);	x1 = SWAP_BYTES(x1);	x2 = SWAP_BYTES(x2);	x3 = SWAP_BYTES(x3);#endif	*(out++) = x0;	*(out++) = x1;	*(out++) = x2;	*(out) = x3;} /* *	Create decryption key */voididea_invert_key(u_int16_t * key, u_int16_t * invKey){	int i;	invKey[KEYS_PER_ROUND * ROUNDS + 0] = inv(*(key++));	invKey[KEYS_PER_ROUND * ROUNDS + 1] = -*(key++);	invKey[KEYS_PER_ROUND * ROUNDS + 2] = -*(key++);	invKey[KEYS_PER_ROUND * ROUNDS + 3] = inv(*(key++));	for (i = KEYS_PER_ROUND * (ROUNDS-1); i >= 0; i -= KEYS_PER_ROUND)	{		invKey[i+4] = *(key++);		invKey[i+5] = *(key++);		invKey[i+0] = inv(*(key++));		if (i > 0)		{			invKey[i+2] = -*(key++);			invKey[i+1] = -*(key++);		}		else		{			invKey[i+1] = -*(key++);			invKey[i+2] = -*(key++);		}		invKey[i+3]=inv(*(key++));	}}/* *	Expand user key of 128 bits to full of 832 bits */voididea_expand_key(u_int16_t * userKey, u_int16_t * key){	int i, j;	for(i = 0; i < 8; i++)		key[i] = SWAP_BYTES(userKey[i]);	j = 0;	for(; i < KEYLEN; i++)	{		j++;		key[j+7] = (key[j & 7] << 9 | key[(j+1) & 7] >> 7);		key += j & 8;		j &= 7;	}}