| 摘要 |
First data to be sent by a sender first party (20) to a recipient second party (30) is encrypted using an encryption key formed using at least a hash value generated using second data and a secret, shared with a trusted party (40), that serves as identification of the sender (20). The second data comprises, for example, one or more conditions that serve as identifiers of the recipient (30), and a hash-value element generated by hashing the first data. The encrypted first data and the encryption key is made available to the recipient (20) which forwards the encryption key to the trusted party (40) with a request for the corresponding decryption key to enable decryption of the received data by the recipient. The trusted party (40) carries out at least one check on the basis of data contained in the encryption key and, if this at least one check is satisfactory, provides a decryption key to the second party. The shared secret may be the private key generated by the trusted party, of a public/private key pair associated with the sender. In another embodiment the shared secret may be a symmetric key. The encryption process effected may be an identifier-based cryptographic process utilising quadratic residuosity or Weil or Tate pairings. |
