A method of generating cryptographically protected digital data encoding content and arranged into messages each message being decodable by a decoder application on a client terminal having a service interface to assemble each message for the decoder application are described. The method can include retrieving a message encrypting at least part of the message; and providing the encrypted messages as output in a format enabling a server service interface to arrange the message into at least one packet including at least one header and a payload. In an example, the encrypted message is assembled by adding a resynchronisation marker, separating a message section from an adjacent message section and including explicit synchronisation information, to at least the further message sections.