decrypt method
Implementation
Map<String, dynamic> decrypt(String base64Encrypted) {
if (privateKey == null) {
throw ArgumentError("Private key required for decryption.");
}
final encryptedBytes = base64Decode(base64Encrypted);
final decryptor = OAEPEncoding(RSAEngine())
..init(false, PrivateKeyParameter<RSAPrivateKey>(privateKey!));
final decryptedBytes = decryptor.process(encryptedBytes);
final jsonString = utf8.decode(decryptedBytes);
return json.decode(jsonString);
}