(Delphi ActiveX) RSA Signature/Verify with .key and .cer

See more RSA Examples

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

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Chilkat ActiveX DLL for Delphi

Chilkat non-ActiveX DLL for Delphi

* The examples here use the ActiveX DLL.

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

...

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

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

privKey := TPrivateKey.Create(Self);

// Load the private key from an RSA .key file:
success := privKey.LoadPemFile('privateKey.key');
if (success <> 1) then
  begin
    Memo1.Lines.Add(privKey.LastErrorText);
    Exit;
  end;

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

rsa := TChilkatRsa.Create(Self);

// Import the private key into the RSA component:
success := rsa.ImportPrivateKey(privKeyXml);
if (success <> 1) then
  begin
    Memo1.Lines.Add(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", "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
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

pubKey := cert.ExportPublicKey();

// 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
    Memo1.Lines.Add(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
    Memo1.Lines.Add(rsa2.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Success.');
end;