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#include "ipcrypt.h"
#define ROTL(X, R) (X) = (unsigned char) ((X) << (R)) | ((X) >> (8 - (R)))
static void
arx_fwd(unsigned char state[4])
{
state[0] += state[1];
state[2] += state[3];
ROTL(state[1], 2);
ROTL(state[3], 5);
state[1] ^= state[0];
state[3] ^= state[2];
ROTL(state[0], 4);
state[0] += state[3];
state[2] += state[1];
ROTL(state[1], 3);
ROTL(state[3], 7);
state[1] ^= state[2];
state[3] ^= state[0];
ROTL(state[2], 4);
}
static void
arx_bwd(unsigned char state[4])
{
ROTL(state[2], 4);
state[1] ^= state[2];
state[3] ^= state[0];
ROTL(state[1], 5);
ROTL(state[3], 1);
state[0] -= state[3];
state[2] -= state[1];
ROTL(state[0], 4);
state[1] ^= state[0];
state[3] ^= state[2];
ROTL(state[1], 6);
ROTL(state[3], 3);
state[0] -= state[1];
state[2] -= state[3];
}
static inline void
xor4(unsigned char *out, const unsigned char *x, const unsigned char *y)
{
out[0] = x[0] ^ y[0];
out[1] = x[1] ^ y[1];
out[2] = x[2] ^ y[2];
out[3] = x[3] ^ y[3];
}
int
ipcrypt_encrypt(unsigned char out[IPCRYPT_BYTES],
const unsigned char in[IPCRYPT_BYTES],
const unsigned char key[IPCRYPT_KEYBYTES])
{
unsigned char state[4];
xor4(state, in, key);
arx_fwd(state);
xor4(state, state, key + 4);
arx_fwd(state);
xor4(state, state, key + 8);
arx_fwd(state);
xor4(out, state, key + 12);
return 0;
}
int
ipcrypt_decrypt(unsigned char out[IPCRYPT_BYTES],
const unsigned char in[IPCRYPT_BYTES],
const unsigned char key[IPCRYPT_KEYBYTES])
{
unsigned char state[4];
xor4(state, in, key + 12);
arx_bwd(state);
xor4(state, state, key + 8);
arx_bwd(state);
xor4(state, state, key + 4);
arx_bwd(state);
xor4(out, state, key);
return 0;
}
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