(Delphi ActiveX) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

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

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

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
pubKey: TPublicKey;
success: Integer;
bdFileData: TChilkatBinData;
bdSig: TChilkatBinData;
rsa: TChilkatRsa;

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

pubKey := TPublicKey.Create(Self);

// Load the public key from an PEM file:
success := pubKey.LoadFromFile('pubKey.pem');
if (success <> 1) then
  begin
    Memo1.Lines.Add(pubKey.LastErrorText);
    Exit;
  end;

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

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

rsa := TChilkatRsa.Create(Self);

// Import the public key into the RSA component:
success := rsa.ImportPublicKeyObj(pubKey.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
    Exit;
  end;

// OpenSSL uses big-endian.
rsa.LittleEndian := 0;

success := rsa.VerifyBd(bdFileData.ControlInterface,'sha256',bdSig.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
    Memo1.Lines.Add('The signature was invalid.');
    Exit;
  end;

Memo1.Lines.Add('The signature was verified.');
end;