Pascal (Lazarus/Delphi)

RSA Sign with PKCS8 Encrypted Key

See more RSA Examples

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

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.PublicKey,
  Chilkat.PrivateKey,
  Chilkat.Rsa,
  Chilkat.Cert;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  privKey: TPrivateKey;
  rsa: TRsa;
  strData: string;
  hexSig: string;
  cert: TCert;
  pubKey: TPublicKey;
  rsa2: TRsa;

begin
  success := False;

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

  privKey := TPrivateKey.Create;

  //  Load the private key from an RSA PEM file:
  success := privKey.LoadAnyFormatFile('raul_privateKey.key','a0123456789');
  if (success = False) then
    begin
      WriteLn(privKey.LastErrorText);
      Exit;
    end;

  rsa := TRsa.Create;

  //  Import the private key into the RSA component:
  success := rsa.UsePrivateKey(privKey);
  if (success = False) then
    begin
      WriteLn(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 = False) then
    begin
      WriteLn(rsa.LastErrorText);
      Exit;
    end;

  WriteLn(hexSig);

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

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

  rsa2 := TRsa.Create;
  success := rsa2.UsePublicKey(pubKey);
  if (success = False) then
    begin
      WriteLn(rsa2.LastErrorText);
      Exit;
    end;

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

  WriteLn('Signature verified!');

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


  privKey.Free;
  rsa.Free;
  cert.Free;
  pubKey.Free;
  rsa2.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.