Abstract: A technique for protecting a cryptographic key. A user has an identifier and an associated password. The first cryptographic key is designed to decrypt a piece of encrypted data. The user device generates a second cryptographic key by applying a key derivation algorithm to at least the password, then encrypts the first cryptographic key by applying an encryption algorithm parameterized by the second cryptographic key. The user device then provides the encryption of the first cryptographic key to a management device for storage. A response associated with a question is obtained from the user. The user device calculates a result of an application of a function to at least one response associated with a question, then provides a value dependent on the result to a management device for storage. The value then enables the user device to determine the password when it has the response to the corresponding question.

Abstract: A technique for protecting a cryptographic key. A user has an identifier and an associated password. The first cryptographic key is designed to decrypt a piece of encrypted data. The user device generates a second cryptographic key by applying a key derivation algorithm to at least the password, then encrypts the first cryptographic key by applying an encryption algorithm parameterized by the second cryptographic key. The user device then provides the encryption of the first cryptographic key to a management device for storage. A response associated with a question is obtained from the user. The user device calculates a result of an application of a function to at least one response associated with a question, then provides a value dependent on the result to a management device for storage. The value then enables the user device to determine the password when it has the response to the corresponding question.

Abstract: A method for detecting intrusions uses a searchable enciphering algorithm and includes: generating a trap bypass key for a security device, which is able to determine keywords characteristic of intrusions, generating by the security device a trap for each keyword by using the trap bypass key; providing the traps to an intrusions detection device; intercepting by the detection device character strings sent on the network by a sender and enciphered with a public key of a receiver; applying by the detection device a test procedure on the character strings enciphered using the traps; and detecting an intrusion on the network if there exists according to the test procedure an enciphered character string representative of a cipher of a keyword.

Abstract: A method for detecting intrusions uses a searchable enciphering algorithm and includes: generating a trap bypass key for a security device, which is able to determine keywords characteristic of intrusions, generating by the security device a trap for each keyword by using the trap bypass key; providing the traps to an intrusions detection device; intercepting by the detection device character strings sent on the network by a sender and enciphered with a public key of a receiver; applying by the detection device a test procedure on the character strings enciphered using the traps; and detecting an intrusion on the network if there exists according to the test procedure an enciphered character string representative of a cipher of a keyword.