Lua

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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Lua

local chilkat = require("chilkat")

-- 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.

local email = chilkat.Email.new()
email.subject = "Signed email"
email.body = "This message will be sent with a digital signature."
email.from = "alice@example.com"
email:add_to("Bob", "bob@example.com")

-- Load the signing certificate (including its private key) from a PFX file.
-- The 2nd argument is the PFX password.
local cert = chilkat.Cert.new()
local success = cert:load_pfx_file("qa_data/certs/signer.pfx", "pfx_password")
if not success then
    print(cert.last_error_text)
    return
end

-- Provide the signing certificate.
success = email:set_signing_cert(cert)
if not success then
    print(email.last_error_text)
    return
end

-- Request that the email be sent with a digital signature.
email.send_signed = true

print("SendSigned = " .. tostring(email.send_signed))

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