Readium LCP employs military-grade encryption to protect e-book contents and to decrypt the contents; a passphrase is needed. This passphrase is determined during the download link (a transaction) creation through our APIs or web UIs.
Once your end-user has their download link and uses it with an LCP-compliant reader application, they will then be shown a passphrase hint (which is again determined during transaction creation), so they can complete fulfillment.
Below is the default instructions page shown to end-users by EditionGuard during fulfillment. You can keep using this page or use a customized version of this page hosted on your web servers.