diff --git a/crypto/encrypt.go b/crypto/encrypt.go
deleted file mode 100644
index bf13054..0000000
--- a/crypto/encrypt.go
+++ /dev/null
@@ -1,59 +0,0 @@
-package crypto
-
-import (
-	"crypto/aes"
-	"crypto/cipher"
-	"crypto/rand"
-	"fmt"
-	"io"
-)
-
-// EncryptWithAES256 encrypts data using a AES256 cryptography.
-func EncryptWithAES256(secretKey, data []byte) ([]byte, error) {
-	if len(secretKey) != 32 {
-		return nil, fmt.Errorf("secret key is not for AES-256: total %d bits", 8*len(secretKey))
-	}
-
-	block, err := aes.NewCipher(secretKey)
-	if err != nil {
-		return nil, err
-	}
-
-	aesGCM, err := cipher.NewGCM(block)
-	if err != nil {
-		return nil, err
-	}
-
-	nonce := make([]byte, aesGCM.NonceSize())
-	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
-		return nil, err
-	}
-
-	cipherText := aesGCM.Seal(nonce, nonce, data, nil)
-
-	return cipherText, nil
-}
-
-// DecryptWithAES256 decrypts data using a AES256 cryptography.
-func DecryptWithAES256(secretKey, ciphertext []byte) ([]byte, error) {
-	if len(secretKey) != 32 {
-		return nil, fmt.Errorf("secret key is not for AES-256: total %d bits", 8*len(secretKey))
-	}
-
-	block, err := aes.NewCipher(secretKey)
-	if err != nil {
-		return nil, err
-	}
-
-	aesgcm, err := cipher.NewGCM(block)
-	if err != nil {
-		return nil, err
-	}
-
-	plainText, err := aesgcm.Open(nil, ciphertext[:aesgcm.NonceSize()], ciphertext[aesgcm.NonceSize():], nil)
-	if err != nil {
-		return nil, err
-	}
-
-	return plainText, nil
-}
diff --git a/event/oracle/event.go b/event/oracle/event.go
index fde70d0..731f5a5 100644
--- a/event/oracle/event.go
+++ b/event/oracle/event.go
@@ -20,7 +20,7 @@ func makeMsgApproveOracleRegistration(uniqueID, approverAddr, targetAddr string,
 	}
 
 	shareKey := crypto.DeriveSharedKey(privKey, pubKey, crypto.KDFSHA256)
-	encryptedOraclePrivKey, err := crypto.EncryptWithAES256(shareKey, oraclePrivKey)
+	encryptedOraclePrivKey, err := crypto.Encrypt(shareKey, nil, oraclePrivKey)
 	if err != nil {
 		return nil, err
 	}