Cryptographic Method and Apparatus

摘要

First data to be sent by a first party (20) to a second party (30) is encrypted using an encryption key string that is formed using at least a hash value of the first data, this hash value being either in clear or in an encrypted form enabling its recovery in clear by a trusted party (40). The encrypted first data and the encryption key string are made available to the second party (20) which forwards the encryption key string to the trusted party (40) with a request for the corresponding decryption key. The trusted party (40) carries out at least one check on the basis of data contained in the encryption key string and, if this at least one check is satisfactory, provides a decryption key to the second party. Where the encryption key string comprises the hash value of the first data in encrypted form, the trusted party (40) will typically decrypt the hash value and pass it to the second party (30) to enable the latter to check the integrity of the first data after decryption with the decryption key.