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1. US20180316490 - Key sequence generation for cryptographic operations

Office United States of America
Application Number 15772933
Application Date 02.11.2016
Publication Number 20180316490
Publication Date 01.11.2018
Grant Number 10742394
Grant Date 11.08.2020
Publication Kind B2
IPC
H04L 9/28
HELECTRICITY
04ELECTRIC COMMUNICATION TECHNIQUE
LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
9Arrangements for secret or secure communication
28using particular encryption algorithm
H04L 9/06
HELECTRICITY
04ELECTRIC COMMUNICATION TECHNIQUE
LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
9Arrangements for secret or secure communication
06the encryption apparatus using shift registers or memories for blockwise coding, e.g. D.E.S. systems
CPC
H04L 2209/24
HELECTRICITY
04ELECTRIC COMMUNICATION TECHNIQUE
LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
2209Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
24Key scheduling, i.e. generating round keys or sub-keys for block encryption
H04L 9/0618
HELECTRICITY
04ELECTRIC COMMUNICATION TECHNIQUE
LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
9Cryptographic mechanisms or cryptographic; arrangements for secret or secure communication
06the encryption apparatus using shift registers or memories for block-wise ; or stream; coding, e.g. DES systems ; or RC4; Hash functions; Pseudorandom sequence generators
0618Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation
Applicants NAGRAVISION S.A.
Inventors Karine Villegas
Brecht Wyseur
Agents Oblon, McClelland, Maier & Neustadt, L.L.P.
Priority Data 1519612.4 06.11.2015 GB
Title
(EN) Key sequence generation for cryptographic operations
Abstract
(EN)

Methods, system and devices are provided that generate a sequence of sub-keys for cryptographic operations from a main key. The main key is operated on only once to generate the sub-keys of the sequence, with a transformation comprising one or more one-way functions. The respective bit values of the sub-keys of the sequence are set using respective bit values of the one or more one-way functions. Advantageously, deriving sub-key bits from respective output bits of one or more one-way functions removes or at least reduces correlations between the main key and the sub-keys, as well as between sub-keys, making it harder or even impossible to recover the main key or other sub-keys from a single sub-key, for example as found using a side-channel attack. At the same time, by using the main key only once (rather than using the main key each time a sub-key is generated), the vulnerability of the main key to a side-channel attack is reduced, because the opportunities for recovering physical information that could lead to the discovery of the main key are reduced. Specific embodiments use parallel or chained execution of sub-functions to generate respective sub-keys. Other specific embodiments generate all sub-keys from a single one-way function in one go.