Abstract: A system for authenticating a user located at a requesting node to a resource such as a host application located at an authenticating node using one-time passwords that change pseudorandomly with each request for authentication. At the requesting node a non-time-dependent value is generated from nonsecret information identifying the user and the host application, using a secret encryption key shared with the authenticating node. The non-time-dependent value is combined with a time-dependent value to generate a composite value that is encrypted to produce an authentication parameter. The authentication parameter is reversibly transformed into an alphanumeric character string that is transmitted as a one-time password to the authenticating node. At the authenticating node the received password is transformed back into the corresponding authentication parameter, which is decrypted to regenerate the composite value.

Abstract: A cryptographic method and apparatus are disclosed which transform a message or arbitrary length into a block of fixed length (128 bits) defined modification detection code (MDC). Although there are a large number of messages which result in the same MDC, because the MDC is a many-to-one function of the input, it is required that it is practically not feasible for an opponent to find them. In analyzing the methods, a distinction is made between two types of attacks, i.e., insiders (who have access to the system) and outsiders (who do not). The first method employs four encryption steps per DEA block and provides the higher degree of security. Coupling between the different DEA operations is provided by using the input keys also as data in two of the four encryption steps. In addition, there is cross coupling by interchanging half of the internal keys.

Abstract: A method for controlling the use of a cryptographic key at a using station by a generating station in a network of generating and using stations is disclosed. A control value specifying the use of the cryptographic key is transmitted with a generated cryptographic key to at least two designated using stations one of which may be the generating station. Each of the generating and using stations have cryptographic facilities that securely store a master key. Two techniques are described for controlling the use of the cryptographic key. In the first, the key and the control value are authenticated via a special authentication code before use by the using station. In the second, the key and control value are coupled during key generation such that the key is recovered only if a correct control value is specified. In addition, two techniques are described for controlling who may use the cryptographic key.