Pascal (Lazarus/Delphi)

Verfies an RSA Signature

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Verifies an RSA signature against the original data. 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.BinData,
  Chilkat.Rsa,
  Chilkat.PublicKey;

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

procedure RunDemo;
var
  success: Boolean;
  bd: TBinData;
  i: Integer;
  bdSig: TBinData;
  pubKey: TPublicKey;
  rsa: TRsa;

begin
  success := False;

  //  The following data was signed by the following example:
  //  RSA Sign using a Private Key on a USB Token or Smartcard
  bd := TBinData.Create;

  for i := 0 to 100 do
    begin
      bd.AppendEncoded('000102030405060708090A0B0C0D0E0F','hex');
    end;

  //  Load the signature
  bdSig := TBinData.Create;
  success := bdSig.LoadFile('rsaSignatures/test1.sig');
  if (success = False) then
    begin
      WriteLn('Failed to load the RSA signature');
      Exit;
    end;

  //  Get the public key to be used for signature verification.
  pubKey := TPublicKey.Create;
  success := pubKey.LoadFromFile('rsaKeys/chilkat-rsa-2048.pem');
  if (success = False) then
    begin
      WriteLn(pubKey.LastErrorText);
      Exit;
    end;

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

  //  Verify the hash of the data against the signature.
  //  We pass in the original data.  Internally, the hash is generated
  //  and used to validate the signature.
  //  Validating the RSA signature means two things:  
  //  (1) the original data is exactly what was signed, and 
  //  (2) it was signed by the owner of the RSA private key.
  success := rsa.VerifyBd(bd,'sha256',bdSig);

  if (success = False) then
    begin
      WriteLn(rsa.LastErrorText);
      WriteLn('Signature invalid.');
    end
  else
    begin
      WriteLn('Signature valid.');
    end;


  bd.Free;
  bdSig.Free;
  pubKey.Free;
  rsa.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.