Lua

Add a Detached Signature with a Separate Private Key

Demonstrates the Chilkat Mime.AddDetachedSignaturePk method, which creates a detached signature using a signer certificate and its separately supplied private key. The first argument is the Cert and the second is the PrivateKey.

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: Sometimes the certificate and its private key live apart — a .cer alongside a PEM key file, for instance — rather than bundled in a single PFX. This method pairs them explicitly for signing, whereas AddDetachedSignature expects a Cert that already provides its key. The result is the same multipart/signed message.

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Lua

local chilkat = require("chilkat")

local mime = chilkat.Mime.new()
local success = mime:set_body_from_plain_text("This message will be signed.")
if not success then
    print(mime.last_error_text)
    return
end

-- Load the certificate and its private key separately.
local cert = chilkat.Cert.new()
success = cert:load_from_file("qa_data/signer.cer")
if not success then
    print(cert.last_error_text)
    return
end

local privKey = chilkat.PrivateKey.new()
success = privKey:load_pem_file("qa_data/signer_privkey.pem")
if not success then
    print(privKey.last_error_text)
    return
end

-- Create a detached signature when the certificate and private key are supplied separately.  The
-- 1st argument is the signer certificate and the 2nd is its private key.
success = mime:add_detached_signature_pk(cert, privKey)
if not success then
    print(mime.last_error_text)
    return
end

success = mime:save_mime("qa_output/signed.eml")
if not success then
    print(mime.last_error_text)
    return
end

print("Detached signature added.")