encryptAES method
Implementation
Uint8List encryptAES(Uint8List key) {
var aesCrypt = AesCryptRaw(key: key, padding: PaddingAES.pkcs7);
var iv = Uint8List.fromList(List<int>.generate(IV_BYTE_LENGTH, (i) => random.nextInt(256)));
return (BytesBuilder()
..add(iv)
..add(aesCrypt.cbc.encrypt(inp: this, iv: iv)))
.toBytes();
}