RSA Signature/Verify with .key and .cer

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

Download Chilkat RSA ActiveX

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
privKey: CHILKATCERTIFICATELib_TLB.IPrivateKey;
success: Integer;
privKeyXml: String;
rsa: TChilkatRsa;
strData: String;
hexSig: String;
cert: TChilkatCert;
pubKey: CHILKATCERTIFICATELib_TLB.IPublicKey;
rsa2: TChilkatRsa;

begin
privKey := TprivateKey.Create(Self).ControlInterface;

//  Load the private key from an RSA .key file:
success := privKey.LoadPemFile('privateKey.key');
if (success <> 1) then
  begin
    ShowMessage(privKey.LastErrorText);
    Exit;
  end;

//  Get the private key in XML format:
privKeyXml := privKey.GetXml();

rsa := TChilkatRsa.Create(Self);

//  Any string argument automatically begins the 30-day trial.
success := rsa.UnlockComponent('30-day trial');
if (success <> 1) then
  begin
    ShowMessage(rsa.LastErrorText);
    Exit;
  end;

//  Import the private key into the RSA component:
success := rsa.ImportPrivateKey(privKeyXml);
if (success <> 1) then
  begin
    ShowMessage(rsa.LastErrorText);
    Exit;
  end;

//  Create the signature as a hex string:
rsa.EncodingMode := 'hex';

strData := 'This is the string to be signed.';

//  Sign the string using the sha-1 hash algorithm.
//  Other valid choices are "md2" and "md5".
hexSig := rsa.SignStringENC(strData,'sha-1');

Memo1.Lines.Add(hexSig);

//  Load a digital certificate from a .cer file:
cert := TChilkatCert.Create(Self);

success := cert.LoadFromFile('myCert.cer');
if (success <> 1) then
  begin
    ShowMessage(cert.LastErrorText);
    Exit;
  end;

pubKey := cert.ExportPublicKey() As CHILKATCERTIFICATELib_TLB.IPublicKey;

//  Now verify using a separate instance of the RSA object:
rsa2 := TChilkatRsa.Create(Self);

//  Import the public key into the RSA object:
success := rsa2.ImportPublicKey(pubKey.GetXml());
if (success <> 1) then
  begin
    ShowMessage(rsa2.LastErrorText);
    Exit;
  end;

//  The signature is a hex string, so make sure the EncodingMode is correct:
rsa2.EncodingMode := 'hex';

//  Verify the signature:
success := rsa2.VerifyStringENC(strData,'sha-1',hexSig);
if (success <> 1) then
  begin
    ShowMessage(rsa2.LastErrorText);
    Exit;
  end;

ShowMessage('Success.');


end;