Lazarus Pascal Requires Chilkat v11.0.0+

Verify an RSA Signature Against the Signed Hash

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the hash that was signed. Lazarus Pascal

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;
  sha256_base64: string;
  base64_rsa_sig: string;
  pubKey: TPublicKey;
  rsa: TRsa;

begin
  success := False;

  bd := TBinData.Create;

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

  sha256_base64 := bd.GetHash('sha256','base64');
  WriteLn('sha256 hash in base64 format: ' + sha256_base64);

  base64_rsa_sig := 'AwF2BbOvL6jA5DwmMAc9n6J2Cc8PI6Rj5W079+aKJcIEtPWRzHor0Bvc3aftGM3Jbgj6SXlIC3M3RYS7UZOnfiHKFNZgbxaNT5WwsWooK42ZkC8DBZl0p7OunBUKd5SciUo+TKilioeUkriN3L1Zl9hwi3HVDVqgVo3XXskwIftSqLSFlepTLTmOWj9Y93dp8J4D9RyLtNgFQBc0WB22tyJTsuY56mLcWe1AMF3LizB9OrbwjynF2u16xWlrJdugccz795fJBUV9aQSD+8S3KeqwQhoi8RK1uhD68aGCyaSpBq0NZ8COAkn7MXaF4POxrAAt8udfHM+PRfSOptcH/w==';

  //  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 against the signature.
  rsa.EncodingMode := 'base64';
  success := rsa.VerifyHashENC(sha256_base64,'sha256',base64_rsa_sig);

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


  bd.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.