Pascal (Lazarus/Delphi)

Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

See more OpenSSL Examples

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

The in.dat file contains the original data that was signed, and can contain text or binary data of any type. The above OpenSSL command does the following:

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

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;
  pubKey: TPublicKey;
  bdFileData: TBinData;
  bdSig: TBinData;
  rsa: TRsa;

begin
  success := False;

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

  pubKey := TPublicKey.Create;

  //  Load the public key from an PEM file:
  success := pubKey.LoadFromFile('pubKey.pem');
  if (success = False) then
    begin
      WriteLn(pubKey.LastErrorText);
      Exit;
    end;

  //  Load the data of the original file that was signed.
  bdFileData := TBinData.Create;
  success := bdFileData.LoadFile('in.dat');

  //  Load the signature.
  bdSig := TBinData.Create;
  success := bdSig.LoadFile('signature.sig');

  rsa := TRsa.Create;

  //  Import the public key into the RSA component:
  success := rsa.UsePublicKey(pubKey);
  if (success = False) then
    begin
      WriteLn(rsa.LastErrorText);
      Exit;
    end;

  //  OpenSSL uses big-endian.
  rsa.LittleEndian := False;

  success := rsa.VerifyBd(bdFileData,'sha256',bdSig);
  if (success <> True) then
    begin
      WriteLn(rsa.LastErrorText);
      WriteLn('The signature was invalid.');
      Exit;
    end;

  WriteLn('The signature was verified.');


  pubKey.Free;
  bdFileData.Free;
  bdSig.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.