# US 10,121,392 B2 · Masking and unmasking methods and devices > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,121,392 B2 - Document ID: US10121392B2 - Status: Granted - Kind: B2 - Application number: 15/439,973 - Filed: 2017-02-23 - Published: 2017-06-08 - Granted: 2018-11-06 - Earliest claimed: 2013-10-09 - Assignees: Idemia France - Applicants: Oberthur Technologies - Inventors: Olivier Chamley; Christophe Giraud - Web page: https://patentgrep.com/patent/US10121392B2 ## CPC - G09C 1/00: 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) - G06F 21/602: {Providing cryptographic facilities or services} - G06F 21/79: in semiconductor storage media, e.g. directly-addressable memories - H04L 9/0631: {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} - H04L 2209/04: Masking or blinding - G09C: CIPHERING OR DECIPHERING APPARATUS FOR CRYPTOGRAPHIC OR OTHER PURPOSES INVOLVING THE NEED FOR SECRECY - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Devices and methods for masking and unmasking sensitive data, based on a standard cryptographic algorithm defining a ciphering algorithm, and a deciphering algorithm using more resources than the ciphering algorithm are described. The masking of sensitive data is done by applying the deciphering algorithm to the sensitive data to obtain masked sensitive data. The unmasking of the masked sensitive data is done by applying the ciphering algorithm to the masked sensitive data to obtain sensitive data in plain form. ## Claims ### Claim 1 A method for personalizing an electronic device, comprising: obtaining sensitive data by way of a third-party device composed of a CPU, a memory having coded instructions stored therein for operating the CPU, and a communications bus in communication with the CPU; at the third-party device, obtaining a masking method selection input and masking the obtained sensitive data using a masking method based on a standard cryptographic algorithm defining a ciphering algorithm, and a deciphering algorithm that uses more resources than the ciphering algorithm, wherein the masking method to mask the obtained sensitive data is determined, based on the masking method selection input, from a first masking method masking the obtained sensitive data by applying the ciphering algorithm to said sensitive data to obtain masked sensitive data and a second masking method masking the sensitive data by applying the deciphering algorithm to said sensitive data to obtain masked sensitive data; and storing the masked sensitive data in the electronic device so as to personalize the electronic device, wherein the masking method selection input depends on a frequency of use of the sensitive data. ### Claim 2 (depends on 1) The method according to claim 1, further comprising: unmasking the masked sensitive data, wherein the unmasking applies the other algorithm between the deciphering and ciphering algorithms than the one applied by the masking method to the masked sensitive data to obtain sensitive data in plain form. ### Claim 3 (depends on 2) The method according to claim 2, wherein the electronic device is configured for also unmasking other masked data, by applying the ciphering or deciphering algorithm of the determined masking method to said other masked data to obtain said other data in plain form. ### Claim 4 (depends on 2) The method according to claim 2, wherein an unmasking with the ciphering algorithm comprises at least one instance of access to a table stored in a memory, and wherein the number of instances of access to the table when unmasking with the ciphering algorithm is less than the number of instances of access to this same table anticipated in the deciphering algorithm. ### Claim 5 (depends on 2) The method according to claim 2, wherein a plurality of instances of access to masked sensitive data is carried out, each instance of access comprising a step of unmasking by applying the other algorithm to the masked sensitive data to obtain sensitive data in plain form. ### Claim 6 (depends on 2) The method according to claim 2, wherein the unmasking step is triggered upon receipt of a request comprising an APDU command compliant with the ISO 7816 standard, such that a response to said request is based on said sensitive data in plain form. ### Claim 7 (depends on 2) The method according to claim 2, wherein the sensitive data in plain form are an authentication key. ### Claim 8 (depends on 2) The method according to claim 2, wherein the standard ciphering algorithm is implemented by a cryptoprocessor, on the basis of the masked sensitive data and a key K. ### Claim 9 (depends on 1) The method according to claim 1, wherein the electronic device is configured for also masking other data, by applying the other algorithm to these other data to obtain other data in plain form. ### Claim 10 (depends on 1) The method according to claim 1, further comprising: applying a key stretching algorithm to a key K, to obtain a sub-key Kn required as input to the step of masking with the ciphering or deciphering algorithm of the determined masking method. ### Claim 11 (depends on 1) The method according to claim 1, wherein the sensitive data are identification elements specific to the electronic device to be personalized. ### Claim 12 (depends on 1) The method according to claim 1, wherein the standard cryptographic algorithm is compliant with the AES standard. ### Claim 13 (depends on 1) The method according to claim 1, wherein the masking method selection input is a user input. ### Claim 14 A system, comprising: an electronic device to be personalized; and a third-party device, incorporating a CPU, a memory and a communications bus in communication with the CPU, the memory having stored therein at least encoded instructions that, upon execution by the CPU, causes the third-party device to function as: a module at the third-party device that obtains sensitive data, a module at the third-party device that obtains a masking method selection input, and masks the obtained sensitive data by operatively implementing a masking method based on a standard cryptographic algorithm defining a ciphering algorithm, and a deciphering algorithm that uses more resources than the ciphering algorithm, by applying the deciphering algorithm to said sensitive data to obtain masked sensitive data, the masking method to mask the obtained sensitive data being determined, based on the masking method selection input, from a first masking method masking the obtained sensitive data by applying the ciphering algorithm to said sensitive data to obtain masked sensitive data and a second masking method masking the sensitive data by applying the deciphering algorithm to said sensitive data to obtain masked sensitive data, where the masking method selection input depends on a frequency of use of the sensitive data, and a module that stores the obtained masked sensitive data in the electronic device, so as to personalize the electronic device. ### Claim 15 (depends on 14) The system according to claim 14, wherein the third-party device is configured to further function as: a module that unmasks masked sensitive data by applying the other algorithm between the deciphering and ciphering algorithms than the one applied by the masking method to the masked sensitive data to obtain sensitive data in plain form. ### Claim 16 (depends on 15) The system according to claim 15, wherein the third-party device is configured to yet further function as: a module that unmasks other masked data, by applying the ciphering or deciphering algorithm to these other masked data to obtain other data in plain form. ### Claim 17 (depends on 14) The system according to claim 14, wherein the third-party device is configured to further function as: a module that masks other data, by applying the ciphering or deciphering algorithm to these other data to obtain other data in plain form. ### Claim 18 (depends on 14) The system according to claim 14, wherein the sensitive data are identification elements specific to the electronic device to be personalized.