# US 2014/0156998 A1 · Challenge-Response Authentication Using a Masked Response Value > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0156998 A1 - Document ID: US20140156998A1 - Status: Published application - Kind: A1 - Application number: 13/690,996 - Filed: 2012-11-30 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: Certicom Corp. - Applicants: Certicom Corp. - Inventors: Robert John Lambert - Web page: https://patentgrep.com/patent/US20140156998A1 ## CPC - G06F 21/44: Program or device authentication - H04L 9/3236: {using cryptographic hash functions} - H04L 9/3271: {using challenge-response} - H04L 9/3273: {for mutual authentication (network architectures or network communication protocols for achieving mutual authentication in a packet data network H04L63/0869)} - G06F 2221/2103: Challenge-response - 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 Challenge-response authentication protocols are disclosed herein, including systems and methods for a first device to authenticate a second device. In one embodiment, the following operations are performed by the first device: (a) sending to the second device: (i) a challenge value corresponding to an expected response value known by the first device, and (ii) a hiding value; (b) receiving from the second device a masked response value; (c) obtaining an expected masked response value from the expected response value and the hiding value; and (d) determining whether the expected masked response value matches the masked response value received from the second device. The operations from the perspective of the second device are also disclosed, which in some embodiments include computing the masked response value using the challenge value, the hiding value, and secret information known to the second device. ## Claims ### Claim 1 A method for a first device to authenticate a second device, the method performed by the first device and comprising: the first device sending to the second device a challenge value corresponding to an expected response value known by the first device, and a hiding value; the first device receiving from the second device a masked response value; the first device obtaining an expected masked response value from the expected response value and the hiding value; the first device determining whether the expected masked response value matches the masked response value received from the second device. ### Claim 2 (depends on 1) The method of claim 1 further comprising repeating the method using a different hiding value. ### Claim 3 (depends on 1) The method of claim 1, wherein the masked response value received from the second device was computed by the second device using the challenge value, the hiding value, and secret information known to the second device. ### Claim 4 (depends on 3) The method of claim 3, wherein the secret information is not known to the first device, and the challenge value and the expected response value are stored on the first device. ### Claim 5 (depends on 1) The method of claim 1, wherein said obtaining the expected masked response value from the expected response value and the hiding value comprises computing the expected masked response value by performing a cryptographic hash of a message that comprises the expected response value and the hiding value. ### Claim 6 (depends on 5) The method of claim 5, wherein the expected masked response value is computed as xmaskres=cryptographic hash(xres∥h), where xmaskres is the expected masked response value, cryptographic hash(•) is the cryptographic hash, xres is the expected response, h is the hiding value, and ∥ represents concatenation. ### Claim 7 (depends on 5) The method of claim 5, wherein the cryptographic hash is one that is progressively computed and is the same as a cryptographic hash used by the second device to compute the masked response value. ### Claim 8 (depends on 7) The method of claim 7, wherein the cryptographic hash does not incorporate a value representing a length of the message into the input of the cryptographic hash. ### Claim 9 (depends on 1) The method of claim 1, wherein the first device is a mobile device and the second device is a battery. ### Claim 10 An device comprising: a memory configured to store a challenge value and an expected response value corresponding to the challenge value; and an interface configured to send to another device the challenge value and a hiding value, and to receive a masked response value from the another device; the device configured to obtain an expected masked response value from the expected response value and the hiding value, and to determine whether the expected masked response value matches the masked response value received from the another device. ### Claim 11 (depends on 10) The device of claim 10, further comprising a processor configured to compute the expected masked response value from the expected response value and the hiding value and to determine whether the expected masked response value matches the masked response value. ### Claim 12 (depends on 10) The device of claim 10, wherein the device is a mobile device and the another device is a battery. ### Claim 13 (depends on 10) The device of claim 10, wherein the device is further configured to obtain different hiding values such that a subsequent hiding value sent to the another device and used in obtaining a subsequent expected masked response value is different from the hiding value. ### Claim 14 (depends on 10) The device of claim 10, wherein the masked response value received from the another device was computed by the another device using the challenge value, the hiding value, and secret information known to the another device. ### Claim 15 (depends on 14) The device of claim 14, wherein the secret information is not known to the device. ### Claim 16 (depends on 10) The device of claim 10, wherein the device is configured to compute the expected masked response value by performing a cryptographic hash of a message that comprises the expected response value and the hiding value. ### Claim 17 A processor readable medium having stored thereon processor readable instructions that, when executed, cause a first device to authenticate a second device by performing operations comprising: sending to the second device a challenge value corresponding to an expected response value known by the first device, and a hiding value; receiving from the second device a masked response value; obtaining an expected masked response value from the expected response value and the hiding value; determining whether the expected masked response value matches the masked response value received from the second device. ### Claim 18 (depends on 17) The processor readable medium of claim 17, wherein the instructions, when executed, further cause the first device to repeat the operations using a different hiding value. ### Claim 19 (depends on 17) The processor readable medium of claim 17, wherein the masked response value received from the second device was computed by the second device using the challenge value, the hiding value, and secret information known to the second device. ### Claim 20 (depends on 19) The processor readable medium of claim 19, wherein the secret information is not known to the first device, and the challenge value and the expected response value are stored on the first device.