Abstract: A system for cryptographically transforming a sequence of input blocks of plaintext or ciphertext data into corresponding sequence of output blocks of data while providing enhanced protection against cryptographic attacks. Each input block is enciphered using a first key to generate a first encryption product, which is combined with a first secret masking value generated independently of the input blocks to generate a masked first encryption product. Each masked first encryption product is then enciphered using a second key to generate a second encryption product, which is combined with a second secret masking value generated independently of the input blocks to generate a masked second encryption product. Finally, each masked second encryption result is enciphered using a third key to generate an output block corresponding to the input block.

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.