Cryptographic method and apparatus

摘要

First data to be sent by a first party to a second party is encrypted using an encryption key that is formed using at least a hash value generated by a keyed hash of at least one condition that typically serves as an identifier of an intended recipient of the first data. The encrypted first data is provided to a data recipient who requests a decryption key from the trusted party. The trusted party is responsible for verifying that the recipient meets the specified conditions before providing the decryption key. A valid decryption key is only provided if the correct conditions have been supplied to the trusted party.