RSA Encryption -- Same Key Different Results

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.

Download Chilkat RSA Public-Key Encryption ActiveX

uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, StdCtrls,
    CHILKATRSALib_TLB,
    OleCtrls;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rsa: TChilkatRsa;
success: Integer;
publicKey: String;
privateKey: String;
plainText: String;
usePrivateKey: Integer;
encryptedStr1: String;
encryptedStr2: String;
rsa2: TChilkatRsa;
decryptedStr1: String;
decryptedStr2: String;

begin
rsa := TChilkatRsa.Create(Self);

success := rsa.UnlockComponent('Anything for 30-day trial');
if (success <> 1) then
  begin
    ShowMessage('RSA component unlock failed');

  end;

//  RSA public key in XML format:
publicKey := '<RSAKeyValue><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>';

privateKey := '<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>';

rsa.ImportPublicKey(publicKey);

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

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

usePrivateKey := 0;
encryptedStr1 := rsa.EncryptStringENC(plainText,usePrivateKey);
Memo1.Lines.Add(encryptedStr1);

//  Do it again. The results are different...
encryptedStr2 := rsa.EncryptStringENC(plainText,usePrivateKey);
Memo1.Lines.Add(encryptedStr2);

//  Now decrypt both strings, and the results are correct
//  in both cases:
rsa2 := TChilkatRsa.Create(Self);
rsa2.ImportPrivateKey(privateKey);
rsa2.EncodingMode := 'base64';
usePrivateKey := 1;

decryptedStr1 := rsa2.DecryptStringENC(encryptedStr1,usePrivateKey);
Memo1.Lines.Add(decryptedStr1);

decryptedStr2 := rsa2.DecryptStringENC(encryptedStr2,usePrivateKey);
Memo1.Lines.Add(decryptedStr2);


end;