Patent ID: 7058605

Claim:
A cryptographic method of enabling a consumer to obtain a document from an owner upon making a payment, the method comprising a step of using a protocol involving the consumer, the owner, a document source and a mediator, wherein the source requires knowledge of a key in which said document is encrypted in order to provide the said document, said key comprising a first portion, a second portion, a third portion, and a fourth portion, the protocol comprising the following sequential steps: (a) the consumer requests a specified document; (b) the owner provides the source with the first and third portions of the key and provides the mediator with the fourth portion of the key, which can combine with the third portion of the key to generate a complete key; (c) the consumer provides the owner with the payment; and either: (d1) the owner provides the source with the second portion of the key and said first portion of the key is combined with said second portion of the key to generate a complete key; or (d2) the owner does not provide the source with the second key portion, and the third key portion is combined with the fourth key portion to generate a complete key.