keeloq.c

/*\从PAWN虚拟机原码中提取的 KeeLoq 算法：
 *  Corrected KeeLoq Encryption and Decryption functions by Ruptor.
 *  Use at your own risk! This source is not copyrighted.
 *  Encoder encrypts an all-0 block, decoder decrypts it.
 *  KeeLoq cipher encrypts 32-bit blocks with 64-bit keys.
 *  Key is XORed with a 32-bit IV incremented on each use.
 *  See http://www.keeloq.boom.ru/decryption.pdf for more details.
 *  KeeLoq algorithm itself is not patented.
\*/
#include "amx.h"

#define KeeLoq_NLF		0x3A5C742E
#define bit(x,n)		(((x)>>(n))&1)
#define g5(x,a,b,c,d,e)	(bit(x,a)+bit(x,b)*2+bit(x,c)*4+bit(x,d)*8+bit(x,e)*16)

uint32_t	KeeLoq_Encrypt (const uint32_t data, const uint64_t key)
{
	uint32_t	x = data, r;

	for (r = 0; r < 528; r++)
	{
		x = (x>>1)^((bit(x,0)^bit(x,16)^(uint32_t)bit(key,r&63)^bit(KeeLoq_NLF,g5(x,1,9,20,26,31)))<<31);
	}
	return x;
}

uint32_t	KeeLoq_Decrypt (const uint32_t data, const uint64_t key)
{
	uint32_t	x = data, r;

	for (r = 0; r < 528; r++)
	{
		x = (x<<1)^bit(x,31)^bit(x,15)^(uint32_t)bit(key,(15-r)&63)^bit(KeeLoq_NLF,g5(x,0,8,19,25,30));
	}
	return x;
}