Objective C - Encryption with AES256 GCM - ios

Question

Currently I'm using the below method for Encryption
+ (NSData*) encrypt:(NSData*)plainText key:(NSData*)key iv:(NSData*)iv {
NSUInteger dataLength = [plainText length];
size_t buffSize = dataLength + kCCBlockSizeAES128;
void *buff = malloc(buffSize);
size_t numBytesEncrypted = 0;
CCCryptorStatus status = CCCrypt(kCCEncrypt, /* kCCEncrypt, etc. */
kCCAlgorithmAES128, /* kCCAlgorithmAES128, etc. */
kCCOptionPKCS7Padding, /* kCCOptionPKCS7Padding, etc. */
key.bytes, kCCKeySizeAES256, /* key and its length */
iv.bytes, /* initialization vector - use random IV everytime */
[plainText bytes], [plainText length], /* input */
buff, buffSize,/* data RETURNED */
&numBytesEncrypted);
if (status == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buff length:numBytesEncrypted];
} else {
// Encryption Failed
}
free(buff);
return nil;
}
I need to use now AES256 GCM for encrypting, I don't see kCCAlgorithmAES256 in CCCrypt. Someone please guide me, I'm using the framework pod 'RNCryptor-objc'.
Below is the decrypt logic handled in backend.
public static byte[] decrypt(byte[] key, byte[] data) {
// TODO utilize GCMAES#decrypt method
try {
if (data.length < NONCE_LENGTH + TAG_LENGTH) {
throw new IllegalArgumentException("data packet too short");
}
int cipherTextLength = data.length - NONCE_LENGTH - TAG_LENGTH;
byte[] nonce = Arrays.copyOf(data, NONCE_LENGTH);
GCMBlockCipher cipher = new GCMBlockCipher(new AESFastEngine());
AEADParameters parameters = new AEADParameters(new KeyParameter(key), TAG_LENGTH * 8, nonce);
cipher.init(false, parameters);
byte[] out = new byte[cipher.getOutputSize(cipherTextLength + TAG_LENGTH)];
int pos = cipher.processBytes(data, NONCE_LENGTH, data.length - NONCE_LENGTH, out, 0);
pos += cipher.doFinal(out, pos);
return Arrays.copyOf(out, pos);
} catch (IllegalStateException | InvalidCipherTextException ex) {
throw new IllegalArgumentException(ex);
}}}