(Delphi ActiveX) Create PKCS7 Attached/Opaque Signature (S/MIME)

Create an S/MIME message with a PKCS7 attached/opaque signature.

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
mime: TChilkatMime;
cert: TChilkatCert;
pfxFilepath: WideString;
pfxPassword: WideString;
success: Integer;

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

mime := TChilkatMime.Create(Self);

// Load a certificate w/ private key for signing.
// There are many ways of getting a certificate object:
// from a pfx file, from .cer and private-key files, from the
// Windows registry-based certificate stores, etc.
// Load a PFX file into a certificate object.
cert := TChilkatCert.Create(Self);
pfxFilepath := 'pfxFiles/something.pfx';
pfxPassword := 'secret';
success := cert.LoadPfxFile(pfxFilepath,pfxPassword);
if (success = 0) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

// Create a very simple MIME message to be signed:
success := mime.AddHeaderField('Subject','This is a test');
success := mime.AddHeaderField('MyCustomHeader','abc123');
mime.ContentType := 'text/plain';
mime.SetBody('This is a plain-text body.');

// Examine the MIME prior to signing:
Memo1.Lines.Add('--- MIME prior to signing ---');
Memo1.Lines.Add(mime.GetMime());

// The MIME prior to signing looks like this:
// -------------------------------------------------------------------------------

// Subject: This is a test
// MyCustomHeader: abc123
// Content-Type: text/plain
// 
// This is a plain-text body.

// -------------------------------------------------------------------------------

// The default hash algorithm used in the signing process is "SHA1".
// To change it, set the SigningHashAlg property:
mime.SigningHashAlg := 'SHA256';

// Convert the MIME to PKCS7 signed-data.
success := mime.ConvertToSigned(cert.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(mime.LastErrorText);
    Exit;
  end;

// Examine the signed MIME
Memo1.Lines.Add('--- MIME converted to PKCS7 signed-data ---');
Memo1.Lines.Add(mime.GetMime());

// The MIME after signing looks like this:
// -------------------------------------------------------------------------------

// Subject: This is a test
// MyCustomHeader: abc123
// Content-Disposition: attachment; filename="smime.p7m"
// Content-Transfer-Encoding: base64
// Content-Type: application/x-pkcs7-mime;
//  name="smime.p7m"; smime-type="signed-data"
// 
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// 

// ------------------------------------------------------------------------------
end;