Delphi DLL

Add an S/MIME Detached Signature

Demonstrates the Chilkat Mime.AddDetachedSignature method, which creates an S/MIME detached signature. The only argument is the signing Cert, which must have access to its private key. On success the entity becomes a multipart/signed with the content and a separate signature part.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A detached signature (multipart/signed) keeps the original content readable alongside a separate signature part — so recipients whose software does not understand S/MIME still see the message, they just cannot verify it. That backward compatibility makes detached the usual choice for signed email. The signer proves authorship with a certificate that carries its private key.

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Delphi DLL

var
success: Boolean;
mime: HCkMime;
pfxPassword: PWideChar;
cert: HCkCert;

begin
success := False;

mime := CkMime_Create();
success := CkMime_SetBodyFromPlainText(mime,'This message will be signed.');
if (success = False) then
  begin
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;
//  Load the signing certificate (which must have access to its private key) from a PFX file.
//  The PFX password should come from a secure source rather than being hard-coded.
pfxPassword := 'myPfxPassword';
cert := CkCert_Create();
success := CkCert_LoadPfxFile(cert,'qa_data/signer.pfx',pfxPassword);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

//  Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
//  original content and a separate signature part.
success := CkMime_AddDetachedSignature(mime,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;

success := CkMime_SaveMime(mime,'qa_output/signed.eml');
if (success = False) then
  begin
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;
Memo1.Lines.Add('Detached signature added.');

CkMime_Dispose(mime);
CkCert_Dispose(cert);