(Delphi ActiveX) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat for Delphi Downloads 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
success: Integer;
privKey: TPrivateKey;
rsa: TChilkatRsa;
strData: WideString;
hexSig: WideString;
cert: TChilkatCert;
pubKey: TPublicKey;
rsa2: TChilkatRsa;

begin
success := 0;

// 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 PEM file:
success := privKey.LoadAnyFormatFile('raul_privateKey.key','a0123456789');
if (success = 0) then
  begin
    Memo1.Lines.Add(privKey.LastErrorText);
    Exit;
  end;

rsa := TChilkatRsa.Create(Self);

// Import the private key into the RSA component:
success := rsa.UsePrivateKey(privKey.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
    Exit;
  end;

// This example will sign a string, and receive the signature
// in a hex-encoded string.  Therefore, set the encoding mode
// to "hex":
rsa.EncodingMode := 'hex';

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

// Sign the string using the sha256 hash algorithm.
// Other valid choices are sha1, sha384, sha512 and others.
hexSig := rsa.SignStringENC(strData,'sha256');
if (rsa.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add(hexSig);

// Now verify with the public key.
// This example shows how to use the public key from 
// a digital certificate (.cer file)
cert := TChilkatCert.Create(Self);
success := cert.LoadFromFile('raul_publicKey.cer');
if (success = 0) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

pubKey := TPublicKey.Create(Self);
cert.GetPublicKey(pubKey.ControlInterface);

rsa2 := TChilkatRsa.Create(Self);
success := rsa2.UsePublicKey(pubKey.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(rsa2.LastErrorText);
    Exit;
  end;

// Verify the signature against the original data:
rsa2.EncodingMode := 'hex';
success := rsa2.VerifyStringENC(strData,'sha256',hexSig);
if (success = 0) then
  begin
    Memo1.Lines.Add(rsa2.LastErrorText);
    Exit;
  end;

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

// Verify with incorrect data:
success := rsa2.VerifyStringENC('something else','sha256',hexSig);
if (success <> 1) then
  begin
    Memo1.Lines.Add('Signature not verified! (which was expected in this case)');
  end
else
  begin
    Memo1.Lines.Add('Hmmm... that''s not right...');
  end;
end;