Delphi DLL

Send an Email with a Digital Signature

Demonstrates the Chilkat Email.SendSigned property. Set it to true to have the email sent with a digital signature (the default is false). Signing also requires a certificate with access to its private key. This example loads that certificate (and its private key) from a PFX file with Cert.LoadPfxFile, supplies it via SetSigningCert, and enables signed sending.

Background: Signing is the mirror image of encrypting. To encrypt for a recipient you use their public certificate; to sign you use your own private key, and recipients verify with your public certificate. A signature does not hide the message — a signed email is still readable by anyone — but it proves who sent it and guarantees the content was not tampered with. A PFX (also called PKCS#12, .pfx or .p12) is a password-protected file that bundles a certificate together with its private key, making it a convenient single-file source for signing credentials.

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var
success: Boolean;
email: HCkEmail;
cert: HCkCert;

begin
success := False;

//  Demonstrates the Email.SendSigned property with a full signing setup.  Set SendSigned
//  to true to have the email sent with a digital signature.  Signing requires a certificate
//  with access to its private key, which we load here from a PFX (.pfx / .p12) file.

email := CkEmail_Create();
CkEmail_putSubject(email,'Signed email');
CkEmail_putBody(email,'This message will be sent with a digital signature.');
CkEmail_putFrom(email,'alice@example.com');
CkEmail_AddTo(email,'Bob','bob@example.com');

//  Load the signing certificate (including its private key) from a PFX file.
//  The 2nd argument is the PFX password.
cert := CkCert_Create();
success := CkCert_LoadPfxFile(cert,'qa_data/certs/signer.pfx','pfx_password');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

//  Provide the signing certificate.
success := CkEmail_SetSigningCert(email,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkEmail__lastErrorText(email));
    Exit;
  end;

//  Request that the email be sent with a digital signature.
CkEmail_putSendSigned(email,True);

Memo1.Lines.Add('SendSigned = ' + IntToStr(Ord(CkEmail_getSendSigned(email))));

//  Note: The path "qa_data/certs/signer.pfx" is a relative local filesystem path,
//  relative to the current working directory of the running application.

CkEmail_Dispose(email);
CkCert_Dispose(cert);