(Delphi DLL) Duplicate Java Verify RSA Signature

Demonstrates how to duplicate a snippet of Java code that verifies an RSA signature.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Cert, Rsa;

...

procedure TForm1.Button1Click(Sender: TObject);
var
base64DataToBeSigned: PWideChar;
base64Certificate: PWideChar;
base64Signature: PWideChar;
cert: HCkCert;
success: Boolean;
rsa: HCkRsa;

begin
// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// This example duplicates the following Java code:

// import com.sun.org.apache.xml.internal.security.utils.Base64;  
// import java.io.ByteArrayInputStream;  
// import java.security.PublicKey;  
// import java.security.Signature;  
// import java.security.cert.CertificateFactory;  
// import java.security.cert.X509Certificate;  
// public class validateSazetak {  
//   public static void main(String[] args) {  
//   String signatureAlgorithm = "SHA256withRSA";  
//   String base64DataToBeSigned = "Hlp...LE4=";  
//   String base64Certificate = "MII...TlQ==";  
//   String base64Signature = "I00...pZA==";  
//   try {  
//       CertificateFactory cf;  
//       X509Certificate certificate = null;  
//       cf = CertificateFactory.getInstance("X.509");  
//       certificate = (X509Certificate) cf.generateCertificate(new 
//       ByteArrayInputStream(Base64.decode(base64Certificate)));  
//        
//       Signature signature = Signature.getInstance(signatureAlgorithm, "SunRsaSign");  
//       PublicKey pk = (PublicKey) certificate.getPublicKey();  
//       signature.initVerify(pk);  
//        
//       byte[] hashBytes = Base64.decode(base64DataToBeSigned);  
//       signature.update(hashBytes);  
//        
//       byte[] sigBytes = Base64.decode(base64Signature);  
//       boolean validity = signature.verify(sigBytes);  
//       System.out.println("Is valid signature:" + validity);  
//     } catch (Exception e) {  
//         System.out.println(e);  
//     }  
// } 

base64DataToBeSigned := 'Hlp...LE4=';
base64Certificate := 'MII...TlQ==';
base64Signature := 'I00...pZA==';

cert := CkCert_Create();
success := CkCert_LoadFromBase64(cert,base64Certificate);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

rsa := CkRsa_Create();

success := CkRsa_SetX509Cert(rsa,cert,False);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

CkRsa_putEncodingMode(rsa,'base64');
success := CkRsa_VerifyStringENC(rsa,base64DataToBeSigned,'sha256',base64Signature);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

Memo1.Lines.Add('Signature verified.');

CkCert_Dispose(cert);
CkRsa_Dispose(rsa);

end;