Reporting purchase of content decrypted via key-sharing

A method for distributing information includes distributing an item of encrypted information to a plurality of clients and distributing respective key-shares to the clients, such that each client will require a key-share that has been distributed to at least one other client in order to reconstruct a key for decrypting the encrypted information. Upon receiving from a first client a report that a second client requested and received a respective one of the key-shares from the first client, a record of a delivery of the item to the second client is made responsively to the report. Enables clients to download encrypted contents whilst on-line and purchase access to them whilst off-line simply by obtaining a key share from a nearby trustworthy client(s) using a local communication link such as BluetoothRTM. Both the trustworthy client(s) and purchasing client notify the content server of sharing of the key, thereby ensuring successful billing for the content even if the purchasing client has ...

Encrypting portions of a content item using different encryption keys

A digital rights management (DRM) system comprises; a content item which has been segmented into at least two portions 250 260, each portion being encrypted according to a different encryption key; a single content rights licence 300 associated with the content item, the licence comprising at least two encrypted decryption keys 310 320 (each able to decrypt at least one portion of the content item), such that one encrypted decryption key is less securely encrypted than another; a plurality of further decryption keys each able to decrypt at least one encrypted decryption key. This system may be used for downloading an e-book (or other media) on an aeroplane, where the decryption key for the first encrypted decryption key is available, but the other decryption key is not available until the purchase is completed (possibly using a smart card) after disembarking the plane (so that only the first part/portion of the e-book is readable on the plane).

Software DRM offline purchase