Abstract: A system for encrypting a plaintext block using a block encryption algorithm having a block size smaller than that of the plaintext block. The plaintext block is transformed into a masked plaintext block using an invertible transformation optionally dependent on additional data and defined such that each bit of the masked plaintext block depends on every bit of the original plaintext block. A subportion of the masked plaintext block is encrypted using the encryption algorithm to generate an encrypted portion of the masked plaintext block. A ciphertext block is generated from the thus encrypted portion of the masked plaintext block and the remaining portion of the masked plaintext block. The ciphertext block is transmitted to a data recipient, who reverses the procedure to recover the original plaintext block.

Abstract: A cryptographic key recovery system for generating a cryptographic key for use by a pair of communicating parties while simultaneously providing for its recovery using one or more key recover agents. A plurality of m-bit shared key parts (P, Q) are generated which are shared with respective key recovery agents, while an n-bit nonshared key part (R) is generated that is not shared with any key recovery agent. The shared key parts (P, Q) are combined to generate an m-bit value which is concatenated with the nonshared key part (R) to generate an (m+n)-bit value from which an encryption key is generated. The cryptographic system has the effective work factor of an n-bit key to all of the key recovery agents acting in concert, but has the effective work factor of an (m+n)-bit to any other combination of third parties.

Abstract: A cryptographic key recovery system that is interoperable with existing systems for establishing keys between communicating parties. The sender uses a reversible key inversion function to generate key recovery values P, Q and (optionally) R as a function of a session key and public information, so that the session key may be regenerated from the key recovery values P, Q and (if generated) R. Key recovery values P and Q are encrypted using the respective public recovery keys of a pair of key recovery agents. The encrypted P and Q values are included along with other recovery information in a session header accompanying an encrypted message sent from the sender to the receiver. The key recovery agents may recover the P and Q values for a law enforcement agent by decrypting the encrypted P and Q values in the session header, using their respective private recovery keys corresponding to the public keys.

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 method and system for detecting authorized programs within a data processing system. The present invention creates a validation structure for validating a program. The validation structure is embedded in the program and in response to an initiation of the program, a determination is made as to whether the program is an authorized program. The determination is made using the validation structure.

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.