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package kcp
import (
"crypto/aes"
"crypto/cipher"
"crypto/md5"
"crypto/rand"
"io"
)
// Entropy defines a entropy source
type Entropy interface {
Init()
Fill(nonce []byte)
}
// nonceMD5 nonce generator for packet header
type nonceMD5 struct {
seed [md5.Size]byte
}
func (n *nonceMD5) Init() { /*nothing required*/ }
func (n *nonceMD5) Fill(nonce []byte) {
if n.seed[0] == 0 { // entropy update
io.ReadFull(rand.Reader, n.seed[:])
}
n.seed = md5.Sum(n.seed[:])
copy(nonce, n.seed[:])
}
// nonceAES128 nonce generator for packet headers
type nonceAES128 struct {
seed [aes.BlockSize]byte
block cipher.Block
}
func (n *nonceAES128) Init() {
var key [16]byte //aes-128
io.ReadFull(rand.Reader, key[:])
io.ReadFull(rand.Reader, n.seed[:])
block, _ := aes.NewCipher(key[:])
n.block = block
}
func (n *nonceAES128) Fill(nonce []byte) {
if n.seed[0] == 0 { // entropy update
io.ReadFull(rand.Reader, n.seed[:])
}
n.block.Encrypt(n.seed[:], n.seed[:])
copy(nonce, n.seed[:])
}
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