Dart Requires Chilkat v11.0.0+

RSA Encryption -- Same Key Different Results

See more RSA Examples

The RSA encryption algorithm produces different results for each call, even when encrypting the same data with the same key. Decryption however, will produce the correct results. This example demonstrates.

*** The reason this occurs is that RSA encryption uses PKCS1 v1.5 padding, and this padding scheme uses random bytes. It is random bytes in the padding that causes the result to be different each time.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example assumes the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final rsa = CkRsa();

  final pubKeyXml = '<RSAPublicKey><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent></RSAPublicKey>';

  final privKeyXml = '<RSAKeyValue><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent><P>4cpW9fvG99Jsz8/AO7PDHTl+pPRAglksrR2kClLV2g9DEeFe/bvmCxLUgMCJ+0eGQ1zA6aA7McKr13zTQ7jKpQ==</P><Q>4cCS/kFlq/P1ExF37Fkh4pCodOEGutepLEG7Q/KljT3ZGlAY+2l8fGu4f+hrkUuGoFl7NOMaJflULoPIgQaq/Q==</Q><DP>lkjcSsvzqh3YKRXJiLNkyf3rypV8noYGU4+oEOsDxilkZfFRDafUPUiiQrRk4ui/d/SzvozU+ZDuWfaOk8PatQ==</DP><DQ>SYCD25i7W8Mwdibn3uIecEAdOQDTSh5RjIFSUYs9b8FFYJXXrHPp/jCsf6jS7RmkGa1Iui1/JAIL8KEjtS7QmQ==</DQ><InverseQ>EDAJa3TpNdPQ3GIdBpnTgFTQY5A60DcszsUW/iCYoXQdPVJ9BLBxVTe9jiLzGuNuzLkVBwQlCy0Bf84hACRV9A==</InverseQ><D>cMFdDYKkddlRNczaugOmOH8b1egpx2liSPs6GYZ2gFObAXJiPK8m+r6c2ckls7hrlUP0DZhi4cG6Tn7xANb0Ek17P7QquVhQYOmFy/YHzm+IJbcwwq7pJHhZBhtcjyXqfUZ+BADGE//GQbrSVwVltpOj5KcxG88NAprLn2MMxfE=</D></RSAKeyValue>';

  final pubKey = CkPublicKey();
  try {
    pubKey.loadFromString(pubKeyXml);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final privKey = CkPrivateKey();
  try {
    privKey.loadXml(privKeyXml);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    rsa.usePublicKey(pubKey);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Encrypt a string and return the encrypted data base64-encoded:
  rsa.encodingMode = 'base64';

  final plainText = 'RSA gives different results with each call, weird but OK';

  var usePrivateKey = false;
  final encryptedStr1 = rsa.encryptStringENC(plainText, usePrivateKey);
  print(encryptedStr1);

  // Do it again. The results are different...
  final encryptedStr2 = rsa.encryptStringENC(plainText, usePrivateKey);
  print(encryptedStr2);

  // Now decrypt both strings, and the results are correct
  // in both cases:
  final rsa2 = CkRsa();
  try {
    rsa2.usePrivateKey(privKey);
  } on ChilkatException {
    print(rsa.lastErrorText);
    return;
  }

  rsa2.encodingMode = 'base64';
  usePrivateKey = true;

  final decryptedStr1 = rsa2.decryptStringENC(encryptedStr1, usePrivateKey);
  print(decryptedStr1);

  final decryptedStr2 = rsa2.decryptStringENC(encryptedStr2, usePrivateKey);
  print(decryptedStr2);
}