ref: 86e0099835f99de6ccc3bee33a297387993aa037
dir: /sys/src/libsec/port/rc4.c/
#include "os.h" #include <libsec.h> void setupRC4state(RC4state *key, uchar *start, int n) { int t; int index2; uchar *state; uchar *p, *e, *sp, *se; state = key->state; se = &state[256]; for(sp = state; sp < se; sp++) *sp = sp - state; key->x = 0; key->y = 0; index2 = 0; e = start + n; p = start; for(sp = state; sp < se; sp++) { t = *sp; index2 = (*p + t + index2) & 255; *sp = state[index2]; state[index2] = t; if(++p >= e) p = start; } } void rc4(RC4state *key, uchar *p, int len) { int tx, ty; int x, y; uchar *state; uchar *e; x = key->x; y = key->y; state = &key->state[0]; for(e = p + len; p < e; p++) { x = (x+1)&255; tx = state[x]; y = (y+tx)&255; ty = state[y]; state[x] = ty; state[y] = tx; *p ^= state[(tx+ty)&255]; } key->x = x; key->y = y; } void rc4skip(RC4state *key, int len) { int tx, ty; int x, y; uchar *state; int i; x = key->x; y = key->y; state = &key->state[0]; for(i=0; i<len; i++) { x = (x+1)&255; tx = state[x]; y = (y+tx)&255; ty = state[y]; state[x] = ty; state[y] = tx; } key->x = x; key->y = y; } void rc4back(RC4state *key, int len) { int tx, ty; int x, y; uchar *state; int i; x = key->x; y = key->y; state = &key->state[0]; for(i=0; i<len; i++) { ty = state[x]; tx = state[y]; state[y] = ty; state[x] = tx; y = (y-tx)&255; x = (x-1)&255; } key->x = x; key->y = y; }