US 11,700,111 B2 · Platform neutral data encryption standard (DES) cryptographic operation

Abstract

Systems and methods for protecting block cipher computation operations from external monitoring attacks. An example apparatus for implementing a block cipher may comprise a memory device to store instructions for computing a block cipher; and a processing device coupled to the memory device. The processing device performs a Data Encryption Standard (DES) cryptographic operation with multiple rounds of a Feistel structure, each round including a substitution function and a transformation function that combines an expansion function and a permutation function into a single operation. The transformation function transforms a first input portion of an internal state of the respective round and a second input portion of the internal state into a first output portion and a second output portion of data. The second output portion is equal to the first input portion and the first output portion is dependent on a combined permutation output from the transformation function.

Claims19

Dependent claims

A computing device comprising:

a memory device to store instructions for computing a block cipher;
and
a processing device coupled to the memory device, wherein the instructions, when executed by the processing device, perform a Data Encryption Standard (DES) cryptographic operation comprising a plurality of rounds of a Feistel structure, each of the plurality of rounds comprising a substitution function and a transformation function that combines an expansion function and a permutation function into a single operation, wherein the transformation function transforms a first input portion of an internal state of the respective round and a second input portion of the internal state into a first output portion and a second output portion of data, wherein the second output portion is equal to the first input portion and the first output portion is dependent on a combined permutation output from the transformation function, wherein the transformation function uses look-up tables, wherein values of the look-up tables are masked with random values, and wherein the random values are such that an output mask of each of the plurality of rounds is the same as an input mask of each of the plurality of rounds.

A method comprising:

receiving, by a processing device, an input value;
and
performing, by the processing device, a Data Encryption Standard (DES) cryptographic operation comprising a plurality of rounds of a Feistel structure, wherein each of the plurality of rounds, comprises:
performing a substitution function on a first input portion of an internal state of the respective round;
and
performing a transformation function on the first input portion into a first output portion, wherein the transformation function combines an expansion function and a permutation function into a single operation, wherein the first output portion is dependent on a combined permutation output from the transformation function, wherein a second input portion of the internal state and a second output portion of data is equal to a second input portion of the internal state of the respective round, wherein performing the transformation function on the first input portion comprises performing a look-up operation in look-up tables, wherein values of the look-up tables are masked with random values, and wherein the random values are such that an output mask of each of the plurality of rounds is the same as an input mask of each of the plurality of rounds.

3 more elements

An integrated circuit comprising:

a cache to store a look-up tables for a transformation function of a block cipher, wherein values of the look-up tables are masked with random values;
and
a processing device coupled to the cache, the processing device to perform a Data Encryption Standard (DES) cryptographic operation comprising a plurality of rounds of a Feistel structure, each of the plurality of rounds comprising a substitution function and the transformation function that combines an expansion function and a permutation function into a single operation, wherein the transformation function transforms a first input portion of an internal state of the respective round and a second input portion of the internal state into a first output portion and a second output portion of data, wherein the second output portion is equal to the first input portion and the first output portion is dependent on a combined permutation output from the transformation function, wherein the transformation function uses the look-up tables, and wherein the random values are such that an output mask of each of the plurality of rounds is the same as an input mask of each of the plurality of rounds.

Dependencies are inferred from the claim text.

Platform neutral data encryption standard (DES) cryptographic operation

Life of this patent

Platform neutral data encryption standard (DES) cryptographic operation

Life of this patent

Abstract

Claims19