mirror of
https://github.com/SamTherapy/dnscrypt.git
synced 2024-12-22 17:00:43 +00:00
24 lines
597 B
Go
24 lines
597 B
Go
package xsecretbox
|
|
|
|
import (
|
|
"errors"
|
|
|
|
"github.com/aead/chacha20/chacha"
|
|
"golang.org/x/crypto/curve25519"
|
|
)
|
|
|
|
// SharedKey computes a shared secret compatible with the one used by `crypto_box_xchacha20poly1305``
|
|
func SharedKey(secretKey [32]byte, publicKey [32]byte) ([32]byte, error) {
|
|
var sharedKey [32]byte
|
|
curve25519.ScalarMult(&sharedKey, &secretKey, &publicKey)
|
|
c := byte(0)
|
|
for i := 0; i < 32; i++ {
|
|
c |= sharedKey[i]
|
|
}
|
|
if c == 0 {
|
|
return sharedKey, errors.New("weak public key")
|
|
}
|
|
var nonce [16]byte
|
|
chacha.HChaCha20(&sharedKey, &nonce, &sharedKey)
|
|
return sharedKey, nil
|
|
}
|