Abstract: Methods and apparatus for enhanced CMEA, or ECMEA, processing. A forward ECMEA and a reverse ECMEA process are provided. The forward ECMEA process decrypts text encrypted by the reverse ECMEA process and the reverse ECMEA process decrypts text encrypted by the forward ECMEA process. The forward ECMEA process employs a first transformation, an iteration of the CMEA process, and a second transformation. The reverse ECMEA process employs a first inverse transformation, an iteration of the CMEA process, and a second inverse transformation. The transformations and inverse transformations, and the iterations of the CMEA process, employ secret offsets to improve security. The transformations and the iteration of the CMEA process also employ an enhanced tbox function using an involutary lookup table.

Abstract: A self-inverting enhanced CMEA encryption system suitable for use in wireless telephony. An unprocessed text message is introduced into the system and subjected to a first iteration of a CMEA process, using a first CMEA key to produce a first intermediate message, a first intermediate processed text message, a first intermediate ciphertext message or the like. The first intermediate processed text message is subjected to a further iteration of the CMEA process, using a second CMEA key, to produce a second intermediate processed text message. The second intermediate processed text message is subjected to a final iteration of the CMEA process, using the first CMEA key, to produce the final processed text message. Security may be additionally enhanced by subjecting each message to an input/output transformation before and after each iteration of the CMEA process.

Abstract: Methods and apparatus for enhanced CMEA, or ECMEA, processing. A forward ECMEA and a reverse ECMEA process are provided. The forward ECMEA process decrypts text encrypted by the reverse ECMEA process and the reverse ECMEA process decrypts text encrypted by the forward ECMEA process. The forward ECMEA process employs a transformation, an iteration of the CMEA process, and an inverse transformation. The reverse ECMEA process employs a reverse transformation, an iteration of the CMEA process, and a reverse inverse transformation. The transformations and inverse transformations, and the iteration of the CMEA process, employ secret offsets to improve security. The transformations and the iteration of the CMEA process also employ an enhanced tbox function using an involutary lookup table.

Abstract: An enhanced CMEA encryption system suitable for use in wireless telephony. A plaintext message is introduced into the system and subjected to a first iteration of a CMEA process, using a first CMEA key to produce an intermediate ciphertext. The intermediate ciphertext is then subjected to a second iteration of the CMEA process using a second CMEA key to produce a final ciphertext. Additional security is achieved by subjecting the plaintext and intermediate ciphertext to input and output transformations before and after each iteration of the CMEA process. The CMEA iterations may be performed using an improved use of a tbox function which adds permutations to a message or intermediate crypto-processed data. Decryption is achieved by subjecting a ciphertext message to the reverse order of the steps used for encryption, replacing the input and output transformations by inverse output and inverse input transformations, respectively, as appropriate.

Abstract: An enhancement to the use of a tbox function for CMEA encryption. Offsets are generated for application of the tbox function to a message, using secret values and previously encrypted message octets. The offsets are used to permute the message for application of the tbox function. For the first message of a call, the previously encrypted message octets are replaced by an initialization value. In a system employing a single iteration of CMEA encryption, first and second offsets are generated. In a system employing two iterations of CMEA encryption, first, second, third and fourth offsets are generated, with the first and second offsets being used in the first iteration of CMEA encryption and the third and fourth offsets being used in the second iteration of CMEA encryption.