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package crypto | ||
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import ( | ||
"bytes" | ||
"crypto/aes" | ||
"crypto/cipher" | ||
"crypto/rand" | ||
"crypto/sha256" | ||
"fmt" | ||
"math/big" | ||
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"github.com/btcsuite/btcd/btcec/v2" | ||
) | ||
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// Encrypt encrypts a message using a public key, returning the encrypted message or an error. | ||
// It generates an ephemeral key, derives a shared secret and an encryption key, then encrypts the message using AES-GCM. | ||
// The ephemeral public key, nonce, tag and encrypted message are then combined and returned as a single byte slice. | ||
func Encrypt(pubKey *btcec.PublicKey, msg []byte) ([]byte, error) { | ||
var pt bytes.Buffer | ||
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ephemeral, err := btcec.NewPrivateKey() | ||
if err != nil { | ||
return nil, fmt.Errorf("failed to generate private key: %v", err) | ||
} | ||
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pt.Write(ephemeral.PubKey().SerializeUncompressed()) | ||
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ecdhKey := btcec.GenerateSharedSecret(ephemeral, pubKey) | ||
hashedSecret := sha256.Sum256(ecdhKey) | ||
encryptionKey := hashedSecret[:16] | ||
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block, err := aes.NewCipher(encryptionKey) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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nonce := make([]byte, 16) | ||
if _, err := rand.Read(nonce); err != nil { | ||
return nil, err | ||
} | ||
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pt.Write(nonce) | ||
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gcm, err := cipher.NewGCMWithNonceSize(block, 16) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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ciphertext := gcm.Seal(nil, nonce, msg, nil) | ||
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tag := ciphertext[len(ciphertext)-gcm.NonceSize():] | ||
pt.Write(tag) | ||
ciphertext = ciphertext[:len(ciphertext)-len(tag)] | ||
pt.Write(ciphertext) | ||
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return pt.Bytes(), nil | ||
} | ||
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// Decrypt decrypts data that was encrypted using the Encrypt function. | ||
// The decrypted message is returned if the decryption is successful, or an error is returned if there are any issues. | ||
func Decrypt(privkey *btcec.PrivateKey, msg []byte) ([]byte, error) { | ||
// Message cannot be less than length of public key (65) + nonce (16) + tag (16) | ||
if len(msg) <= (1 + 32 + 32 + 16 + 16) { | ||
return nil, fmt.Errorf("invalid length of message") | ||
} | ||
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pb := new(big.Int).SetBytes(msg[:65]).Bytes() | ||
pubKey, err := btcec.ParsePubKey(pb) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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ecdhKey := btcec.GenerateSharedSecret(privkey, pubKey) | ||
hashedSecret := sha256.Sum256(ecdhKey) | ||
encryptionKey := hashedSecret[:16] | ||
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msg = msg[65:] | ||
nonce := msg[:16] | ||
tag := msg[16:32] | ||
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ciphertext := bytes.Join([][]byte{msg[32:], tag}, nil) | ||
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block, err := aes.NewCipher(encryptionKey) | ||
if err != nil { | ||
return nil, fmt.Errorf("cannot create new aes block: %w", err) | ||
} | ||
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gcm, err := cipher.NewGCMWithNonceSize(block, 16) | ||
if err != nil { | ||
return nil, fmt.Errorf("cannot create gcm cipher: %w", err) | ||
} | ||
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plaintext, err := gcm.Open(nil, nonce, ciphertext, nil) | ||
if err != nil { | ||
return nil, fmt.Errorf("cannot decrypt ciphertext: %w", err) | ||
} | ||
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return plaintext, nil | ||
} |
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@@ -0,0 +1,30 @@ | ||
package crypto | ||
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import ( | ||
"encoding/hex" | ||
"fmt" | ||
"testing" | ||
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"github.com/btcsuite/btcd/btcec/v2" | ||
"github.com/cometbft/cometbft/crypto/secp256k1" | ||
"github.com/stretchr/testify/assert" | ||
) | ||
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func TestEncryptAndDecrypt(t *testing.T) { | ||
secret := []byte("secret") | ||
privateKey := secp256k1.GenPrivKeySecp256k1(secret) | ||
priv, _ := btcec.PrivKeyFromBytes(privateKey) | ||
publicKey := priv.PubKey() | ||
message := []byte("Hello, this is a test message.") | ||
encryptedMessage, err := Encrypt(publicKey, message) | ||
if !assert.NoError(t, err) { | ||
return | ||
} | ||
fmt.Println("Encrypted Message:", hex.EncodeToString(encryptedMessage)) | ||
decryptedMessage, err := Decrypt(priv, encryptedMessage) | ||
if !assert.NoError(t, err) { | ||
return | ||
} | ||
fmt.Println("Decrypted Message:", string(decryptedMessage)) | ||
assert.Equal(t, string(message), string(decryptedMessage)) | ||
} |