[Vespasian]

It's a "voucher" for an epub/pdf protected by Adobe DRM.

After purchasing a book "you" get an ASCM file and use it to

a) download an encrypted file from a content server

and b) get the encryption keys protected via a PKS system.

This was cracked a few years ago and apparently Adobe/vendors never upgraded.

[Tajnymag]

Wow, that sounds even worse than I imagined.