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 32-bit Chilkat RSA ActiveX (.msi)

Download All 32-bit Chilkat ActiveX Components (.zip)

Download All 64-bit Chilkat ActiveX Components (.zip)

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';

//  If some other non-Chilkat application or web service is going to be verifying
//  the signature, it is important to match the byte-ordering.
//  The LittleEndian property may be set to 1
//  for little-endian byte ordering,
//  or 0  for big-endian byte ordering.
//  Microsoft apps typically use little-endian, while
//  OpenSSL and other services (such as Amazon CloudFront)
//  use big-endian.
rsa.LittleEndian := 0;

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

//  Sign the string using the sha-1 hash algorithm.
//  Other valid choices are "md2", "sha256", "sha384",
//  "sha512", 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;