26 lines
644 B
Go
26 lines
644 B
Go
package kcp
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import (
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"crypto/md5"
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"crypto/rand"
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"io"
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)
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// nonceMD5 is a nonce generator for each packet header
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// which took the advantages of both MD5 and CSPRNG(like /dev/urandom).
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// The benchmark shows it's faster than previous CSPRNG only method.
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type nonceMD5 struct {
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data [md5.Size]byte
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}
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// Nonce fills a nonce into the provided slice with no more than md5.Size bytes
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// the entropy will be updated whenever a leading 0 appears
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func (n *nonceMD5) Fill(nonce []byte) {
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if n.data[0] == 0 { // 1/256 chance for entropy update
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io.ReadFull(rand.Reader, n.data[:])
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}
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n.data = md5.Sum(n.data[:])
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copy(nonce, n.data[:])
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return
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}
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