看了下NewCipher:
// NewCipher creates and returns a new Cipher. The key argument should be the
// RC4 key, at least 1 byte and at most 256 bytes.
func NewCipher(key []byte) (*Cipher, error) {
k := len(key)
if k < 1 || k > 256 {
return nil, KeySizeError(k)
}
var c Cipher
for i := 0; i < 256; i++ {
c.s[i] = uint8(i)
}
var j uint8 = 0
for i := 0; i < 256; i++ {
j += c.s[i] + key[i%k]
c.s[i], c.s[j] = c.s[j], c.s[i]
}
return &c, nil
}
XORKeyStream:
// XORKeyStream sets dst to the result of XORing src with the key stream.
// Dst and src may be the same slice but otherwise should not overlap.
func (c *Cipher) XORKeyStream(dst, src []byte) {
for i := range src {
c.i += 1
c.j += c.s[c.i]
c.s[c.i], c.s[c.j] = c.s[c.j], c.s[c.i]
dst[i] = src[i] ^ c.s[c.s[c.i]+c.s[c.j]]
}
}
这里并不是简单的异或运算,所以执行两次以后不会有xor运算的性质