PureBasic

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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IncludeFile "CkEmail.pb"
IncludeFile "CkCert.pb"

Procedure ChilkatExample()

    success.i = 0

    ;  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.i = CkEmail::ckCreate()
    If email.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkEmail::setCkSubject(email, "Signed email")
    CkEmail::setCkBody(email, "This message will be sent with a digital signature.")
    CkEmail::setCkFrom(email, "alice@example.com")
    CkEmail::ckAddTo(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.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkCert::ckLoadPfxFile(cert,"qa_data/certs/signer.pfx","pfx_password")
    If success = 0
        Debug CkCert::ckLastErrorText(cert)
        CkEmail::ckDispose(email)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ;  Provide the signing certificate.
    success = CkEmail::ckSetSigningCert(email,cert)
    If success = 0
        Debug CkEmail::ckLastErrorText(email)
        CkEmail::ckDispose(email)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ;  Request that the email be sent with a digital signature.
    CkEmail::setCkSendSigned(email, 1)

    Debug "SendSigned = " + Str(CkEmail::ckSendSigned(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::ckDispose(email)
    CkCert::ckDispose(cert)


    ProcedureReturn
EndProcedure