Delphi DLL

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.

Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, BinData, Rsa, PublicKey;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
pubKey: HCkPublicKey;
bdFileData: HCkBinData;
bdSig: HCkBinData;
rsa: HCkRsa;

begin
success := False;

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

pubKey := CkPublicKey_Create();

// Load the public key from an PEM file:
success := CkPublicKey_LoadFromFile(pubKey,'pubKey.pem');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey));
    Exit;
  end;

// Load the data of the original file that was signed.
bdFileData := CkBinData_Create();
success := CkBinData_LoadFile(bdFileData,'in.dat');

// Load the signature.
bdSig := CkBinData_Create();
success := CkBinData_LoadFile(bdSig,'signature.sig');

rsa := CkRsa_Create();

// Import the public key into the RSA component:
success := CkRsa_UsePublicKey(rsa,pubKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

// OpenSSL uses big-endian.
CkRsa_putLittleEndian(rsa,False);

success := CkRsa_VerifyBd(rsa,bdFileData,'sha256',bdSig);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Memo1.Lines.Add('The signature was invalid.');
    Exit;
  end;

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

CkPublicKey_Dispose(pubKey);
CkBinData_Dispose(bdFileData);
CkBinData_Dispose(bdSig);
CkRsa_Dispose(rsa);

end;