void rc4_set_key(RC4_CTX *ctx, unsigned char *key, int key_len)
{
int i = 0;
unsigned char x = 0, y = 0;
unsigned char *S = ctx->S;
ctx->x = x = 0;
ctx->y = y = 0;
for (i = 0; i < 256; i++)
{
S[i] = (unsigned char)i;
}
for (i = 0; i < 256; i++)
{
y = (y + S[i] + key[x]) & 0xff;
rc4_swap(&S[i], &S[y]);
if (++x >= key_len)
{
x = 0;
}
}
}
void rc4_encrypt(RC4_CTX *ctx, uint8_t *buffer, size_t length) {
for (size_t idx = 0; idx < length; idx++) {
ctx->i++;
ctx->j += ctx->S[ctx->i];
rc4_swap(ctx, ctx->i, ctx->j);
uint8_t K = ctx->S[(ctx->S[ctx->i] + ctx->S[ctx->j]) % 256];
buffer[idx] ^= K;
}
}
void rc4_init(RC4_CTX *ctx, const uint8_t *key, size_t length) {
ctx->i = 0;
ctx->j = 0;
for (size_t i = 0; i < 256; i++) {
ctx->S[i] = i;
}
uint8_t j = 0;
for (size_t i = 0; i < 256; i++) {
j += ctx->S[i] + key[i % length];
rc4_swap(ctx, i, j);
}
}
void
rc4_transform(rc4_sbox_t *rc4_sbox, unsigned char *buffer_ptr, unsigned int buffer_len)
{
unsigned int i;
for(i = 0; i < buffer_len; i ++)
{
// The pseudo-random generation algorithm
rc4_sbox->x = (rc4_sbox->x + 1) & 0xff;
rc4_sbox->y = (rc4_sbox->y + rc4_sbox->state[rc4_sbox->x]) & 0xff;
rc4_swap(rc4_sbox->state[rc4_sbox->x], rc4_sbox->state[rc4_sbox->y]);
unsigned char keyChar = rc4_sbox->state[(rc4_sbox->state[rc4_sbox->x] + rc4_sbox->state[rc4_sbox->y]) & 0xff];
if(buffer_ptr) // NULL when seeking
buffer_ptr[i] ^= keyChar;
}
}
void rc4_crypt(RC4_CTX *ctx, unsigned char *data, int data_len)
{
int i = 0;
unsigned char x = 0, y = 0;
unsigned char *S = ctx->S;
for (i = 0; i < data_len; i++)
{
x = (x + 1) & 0xff;
y = (y + S[x]) & 0xff;
rc4_swap(&S[x], &S[y]);
data[i] ^= S[(S[x] + S[y]) & 0xff];
}
ctx->x = x;
ctx->y = y;
}
void
rc4_init(rc4_sbox_t *rc4_sbox, const unsigned char *key_ptr, unsigned int key_len)
{
rc4_sbox->x = 0;
rc4_sbox->y = 0;
// Initialisation of the permutation
unsigned int i;
for(i = 0; i < 256; i++)
rc4_sbox->state[i] = (char)i;
// Mixing permutation
unsigned int j = 0;
unsigned int k;
for(i = 0; i < 256; i++)
{
k = i % key_len;
j = (key_ptr[k] + rc4_sbox->state[i] + j) & 0xff;
rc4_swap(rc4_sbox->state[i], rc4_sbox->state[j]);
}
}
