29 lines
797 B
Go
29 lines
797 B
Go
package engine
|
|
|
|
import (
|
|
"crypto/sha256"
|
|
"fmt"
|
|
"io"
|
|
|
|
"golang.org/x/crypto/hkdf"
|
|
)
|
|
|
|
// deriveKey derives a symmetric key from two shared secrets using HKDF-SHA256
|
|
func deriveKey(ss1, ss2, salt []byte) ([]byte, error) {
|
|
ikm := append(ss1, ss2...)
|
|
kdf := hkdf.New(sha256.New, ikm, salt, []byte(HKDFInfo))
|
|
symmetricKey := make([]byte, KeySize)
|
|
if _, err := io.ReadFull(kdf, symmetricKey); err != nil {
|
|
return nil, fmt.Errorf("key derivation failed: %w", err)
|
|
}
|
|
return symmetricKey, nil
|
|
}
|
|
|
|
// buildAAD constructs the associated authenticated data from public keys
|
|
func buildAAD(ephemeralPubBytes, senderPubBytes []byte) []byte {
|
|
aad := make([]byte, 0, len(ephemeralPubBytes)+len(senderPubBytes))
|
|
aad = append(aad, ephemeralPubBytes...)
|
|
aad = append(aad, senderPubBytes...)
|
|
return aad
|
|
}
|