Lua

Encrypt MIME for a Recipient Certificate

Demonstrates encrypting the current MIME entity for a single recipient using the Mime.Encrypt method. The entity is replaced with CMS/PKCS #7 encrypted S/MIME that only the holder of the recipient's private key can read.

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. S/MIME encryption uses the recipient's public certificate to protect a message so that only the matching private key can recover it. The recipient certificate must be RSA-based. Only the recipient's public key is needed to encrypt—the private key is required to decrypt.

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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 encrypted.")
if not success then
    print(mime.last_error_text)
    return
end

-- Load the recipient's certificate (public key only is sufficient for encrypting).
local cert = chilkat.Cert.new()
success = cert:load_from_file("qa_data/recipient.cer")
if not success then
    print(cert.last_error_text)
    return
end

-- Encrypt for the recipient.  The entity is replaced with CMS/PKCS #7 encrypted S/MIME that only
-- the holder of the recipient's private key can decrypt.  The certificate must be RSA-based.
success = mime:encrypt(cert)
if not success then
    print(mime.last_error_text)
    return
end

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

print("Message encrypted.")