Cryptographic key, or other secret material, recovery

摘要

Secret material, such as a cryptographic key, that is needed for operation of a computer system (4a), can be stored under password protection on a storage medium for insertion into the computer system as required. If the password is forgotten, or the storage medium is faulty, the secret material will not be accessible. To permit secure recovery of the secret material in these or other circumstances, the secret material is encrypted using a recovery key and stored on the computer system, together with a value used in the generation of the recovery key from the secret material. The secret material is also stored on a remote secure system (5). When recovery of the secret material is required, the value for generating the recovery key is supplied to the remote system and used to generate the recovery key there. The generated recovery key is then supplied to the computer system, where it is used to decrypt the secret material. A new recovery key is then generated using a different value for a future recovery instance. The value can be supplied to the remote system (5) by dictation of a corresponding alphanumeric expression by a computer system operator (6), over a telephone connection (7, 8, 9) to a support technician (10) at the remote system for input thereat, and another alphanumeric expression corresponding to the generated recovery key can be dictated back to the computer system operator for insertion into the computer system and subsequent decryption of the secret material, thus allowing operation of the computer system, in circumstances where there is no data connection link between the two systems.