XChaCha20-Poly1305: encryption with nonce appended to ciphertext

Author: pilinux

_example/xchacha20poly1305/main.go

@@ -45,4 +45,20 @@ func main() {
 		return
 	}
 	fmt.Println("plaintext:", plaintext)
+
+	// encrypt the data using EncryptXChacha20poly1305WithNonceAppended function
+	ciphertext, err = crypt.EncryptXChacha20poly1305WithNonceAppended(key, text)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Println("ciphertext:", ciphertext)
+
+	// decrypt the data using DecryptXChacha20poly1305WithNonceAppended function
+	plaintext, err = crypt.DecryptXChacha20poly1305WithNonceAppended(key, ciphertext)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Println("plaintext:", plaintext)
 }

chaCha20.go

@@ -129,3 +129,29 @@ func DecryptXChacha20poly1305(key, nonce, ciphertext []byte) (text string, err e
 
 	return
 }
+
+// EncryptXChacha20poly1305WithNonceAppended encrypts and authenticates the given message with
+// XChaCha20-Poly1305 AEAD using the given 256-bit key and 192-bit nonce.
+// It appends the ciphertext to the nonce [ciphertext = nonce + ciphertext].
+func EncryptXChacha20poly1305WithNonceAppended(key []byte, text string) (ciphertext []byte, err error) {
+	ciphertext, nonce, err := EncryptXChacha20poly1305(key, text)
+	if err != nil {
+		return
+	}
+	ciphertext = append(nonce, ciphertext...)
+	return
+}
+
+// DecryptXChacha20poly1305WithNonceAppended decrypts and authenticates the given message with
+// XChaCha20-Poly1305 AEAD using the given 256-bit key and 192-bit nonce.
+// It expects the ciphertext along with the nonce [ciphertext = nonce + ciphertext].
+func DecryptXChacha20poly1305WithNonceAppended(key, ciphertext []byte) (text string, err error) {
+	nonceSize := chacha20poly1305.NonceSizeX
+	if len(ciphertext) < nonceSize {
+		err = errors.New("ciphertext is too short")
+		return
+	}
+	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
+	text, err = DecryptXChacha20poly1305(key, nonce, ciphertext)
+	return
+}