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encryption.go
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encryption.go
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package node
import (
"crypto/rand"
"errors"
"fmt"
"golang.org/x/crypto/nacl/box"
)
// for encryption
const (
nonceSize = 24
SharedKeySize = 32
)
var EmptyNonce [nonceSize]byte
func EncryptMessage(message []byte, sharedKey *[SharedKeySize]byte) []byte {
if sharedKey == nil {
return append(EmptyNonce[:], message...)
}
var nonce [nonceSize]byte
_, err := rand.Read(nonce[:])
if err != nil {
return nil
}
encrypted := make([]byte, len(message)+box.Overhead+nonceSize)
copy(encrypted[:nonceSize], nonce[:])
box.SealAfterPrecomputation(encrypted[nonceSize:nonceSize], message, &nonce, sharedKey)
return encrypted
}
func DecryptMessage(message []byte, sharedKey *[SharedKeySize]byte) ([]byte, bool, error) {
if len(message) < nonceSize {
return nil, false, fmt.Errorf("encrypted message should have at least %d bytes", nonceSize)
}
var nonce [nonceSize]byte
copy(nonce[:], message[:nonceSize])
if nonce == EmptyNonce {
return message[nonceSize:], false, nil
}
if sharedKey == nil {
return nil, false, errors.New("cannot decrypt message: no shared key yet")
}
if len(message) < nonceSize+box.Overhead {
return nil, false, fmt.Errorf("encrypted message should have at least %d bytes", nonceSize+box.Overhead)
}
decrypted := make([]byte, len(message)-nonceSize-box.Overhead)
_, ok := box.OpenAfterPrecomputation(decrypted[:0], message[nonceSize:], &nonce, sharedKey)
if !ok {
return nil, false, errors.New("decrypt message failed")
}
return decrypted, true, nil
}