(Delphi DLL) A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

Demonstrates how to use an A3 or A4 certificate w/ private key on a smartcard or token to create a PKCS7 opaque signature, and also how to verify an opaque signature.

An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Cert, Crypt2;

...

procedure TForm1.Button1Click(Sender: TObject);
var
crypt: HCkCrypt2;
cert: HCkCert;
success: Boolean;
originalData: PWideChar;
opaqueSig: PWideChar;
vCrypt: HCkCrypt2;
extractedData: PWideChar;

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

crypt := CkCrypt2_Create();

// A certificate and private key is needed to create a signature.
// Chilkat provides many different ways to load a certificate and private key, such
// as from a smartcards and hardware tokens, PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
// This example will load the default certificate from the smartcard that is currently in
// the smartcard reader.

cert := CkCert_Create();

// If the smartcard or token requires a PIN, we can set it here to avoid the dialog...
CkCert_putSmartCardPin(cert,'000000');

success := CkCert_LoadFromSmartcard(cert,'');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

// Tell it to use the cert and private key we've loaded.
success := CkCrypt2_SetSigningCert(crypt,cert);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(crypt));
    Exit;
  end;

// Indicate we want the opaque signature in base64 format:
CkCrypt2_putEncodingMode(crypt,'base64');

// Sign the string using the "utf-8" byte representation:
CkCrypt2_putCharset(crypt,'utf-8');

// Create the opaque signature:
originalData := 'This is the string to be signed.';
opaqueSig := CkCrypt2__opaqueSignStringENC(crypt,originalData);
if (CkCrypt2_getLastMethodSuccess(crypt) <> True) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(crypt));
    Exit;
  end;

Memo1.Lines.Add(opaqueSig);

// The output looks like this:
// MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

// ----------------------------------------------------------------------------------------------
// Now let's verify the signature and retrieve the original data.
// We'll use a new Crypt2 object to keep things completely separate...

vCrypt := CkCrypt2_Create();

// We only need the certificate to verify a signature (and extract the data from
// an opaque signature).  The public key is always embedded within a certificate.
success := CkCrypt2_SetVerifyCert(vCrypt,cert);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(vCrypt));
    Exit;
  end;

CkCrypt2_putEncodingMode(vCrypt,'base64');
CkCrypt2_putCharset(vCrypt,'utf-8');

extractedData := CkCrypt2__opaqueVerifyStringENC(vCrypt,opaqueSig);
if (CkCrypt2_getLastMethodSuccess(vCrypt) <> True) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(vCrypt));
    Exit;
  end;

Memo1.Lines.Add('The extracted data: ' + extractedData);

// The output is:
// The extracted data: This is the string to be signed.

CkCrypt2_Dispose(crypt);
CkCert_Dispose(cert);
CkCrypt2_Dispose(vCrypt);

end;