Area efficient cryptographic method and apparatus

Patent metadata

Field	Value
Publication number	US-9900149-B2
Application number	US-201414459708-A
Country	US
Kind code	B2
Filing date	Aug 14, 2014
Priority date	Dec 24, 2013
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

A method of improving the efficiency of an encryption/decryption process implementing the NIST FIPS 197 standard which includes a substitution box (S-box) and an inverse substitution (inverse S-box), comprises concatenating the S-box and inverse S-box to form a combined lookup table, and folding the concatenated table to generate a folded lookup table. The folded lookup table may be indexed for an encryption operation and for a decryption operation using a signal indicative of whether encryption or decryption is used.

First claim

What is claimed is:

1. A method of improving efficiency of encryption/decryption process that includes a substitution box (S-box) implemented as a first lookup table and an inverse substitution box (inverse S-box) implemented as a second lookup table, said method comprising generating a combined lookup table by comparing the two lookup tables and inserting within the combined lookup table a value from the lookup tables when the value matches and a polarity for a control bit when the values are different.

2. The method of claim 1 which includes indexing the combined lookup table for an encryption operation and for a decryption operation using a signal indicative of whether encryption or decryption is used.

3. The method of claim 1 in which the combined lookup table is responsive to said index to provide a first output value for a first operation, and a second different output value for a second other operation.

4. The method of claim 1 which includes inserting within an output value one of a fixed value and a calculated value, the calculated value being based on a control bit, and the output value comprising symbols including at least one fixed value and at least one calculated value.

5. An encryption/decryption system that includes a second lookup table, said system comprising a memory containing a combined lookup table formed by comparing the two lookup tables and inserting within the combined lookup table a value from the lookup tables when the value matches and a polarity for a control bit when the values are different to produce a combined lookup table that is smaller than the combination of the first and second lookup table, and a processor adapted to encrypt and decrypt data according using said combined table.

6. The system of claim 5 in which said combined lookup table is indexed using a signal indicative of whether encryption or decryption is to be performed.

7. The system of claim 5 which includes a cipher circuit comprising a memory having the combined lookup table stored therein; an indexing circuit for retrieving from the combined lookup table, a lookup table value used to form at least part of an output value, the lookup table value comprising a plurality of symbols; and a processing circuit for processing some of the plurality of symbols within the output value based on a present operation, such that a value is associated with the symbols within the output value to provide different output values for a same index for different present operations.

8. The system of claim 5 in which the combined lookup table includes variable values dependent on the encryption or decryption operation being performed, and fixed values that are fixed for each operation.

Assignees

• Synopsys Inc

Inventors

• Adikari A A Jithra
• Borza Michael

Classifications

• H04L2209/122

  Hardware reduction or efficient architectures · CPC title

• H04L9/0631 Primary

  Substitution permutation network [SPN], i.e. cipher composed of a number of stages or rounds each involving linear and nonlinear transformations, e.g. AES algorithms · CPC title

• H04L2209/30

  Compression, e.g. Merkle-Damgard construction · CPC title

• G09C1/00

  Apparatus or methods whereby a given sequence of signs, e.g. an intelligible text, is transformed into an unintelligible sequence of signs by transposing the signs or groups of signs or by replacing them by others according to a predetermined system (cryptographic typewriters G09C3/00) · CPC title

• H04L9/32

  including means for verifying the identity or authority of a user of the system {or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials} · CPC title