# US 8,543,812 B2 · Efficient and secure cryptographic coupon reloading > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,543,812 B2 - Document ID: US8543812B2 - Status: Granted - Kind: B2 - Application number: 12/666,873 - Filed: 2008-06-26 - Published: 2010-07-22 - Granted: 2013-09-24 - Earliest claimed: 2007-06-29 - Assignees: France Telecom - Applicants: Matthew Robshaw; Henri Gilbert; Marc Girault; Loic Juniot - Inventors: Matthew Robshaw; Henri Gilbert; Marc Girault; Loic Juniot - Web page: https://patentgrep.com/patent/US8543812B2 ## CPC - H04L 9/3271: {using challenge-response} - H04L 9/3236: {using cryptographic hash functions} - H04L 2209/805: Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A system and a method for cryptographic reduced-coupon reloading are provided, where a coupon includes a pseudo-random number ri=PRFK(i), where i is an index for labeling the coupon, PRF is a predetermined pseudo-random function and K is a regeneration key, and a “reduced-coupon” xi=ƒ(ri), where ƒ is a predetermined one-way function, where: a candidate device and a second device acquire a common value of a token T, the candidate device transmits a verification value vT to the second device, the second device verifies whether the verification value is equal to PRF′Q(T), where PRF′ is a predetermined keyed pseudo-random function identical to, or derived from, the pseudo-random function PRF, where Q is an authentication key owned by the second device and known to the candidate device provided the candidate device is a legitimate reloading device, and if the verification is positive, one or several reduced-coupon(s) provided by the candidate device are stored in the second device. ## Claims ### Claim 1 A method for cryptographic reduced-coupon reloading, wherein a coupon comprises a pseudo-random number ri=PRFK(i), where i is an index for labeling the coupon, PRF is a predetermined pseudo-random function and K is a regeneration key, and a “reduced-coupon” xi such that xi=ƒ(ri), where ƒ is a predetermined one-way function, said method comprising the following steps: verifying that a number of reduced-coupons xi that are pre-stored in a second device has reached a predetermined low amount, acquiring, by a candidate device and the second device, a common value of a token T, transmitting from said candidate device a verification value vT to the second device, verifying, by the second device whether said verification value vT is given by vT=PRF′Q(T), where PRF′ is a predetermined keyed pseudo-random function identical to, or derived from, said pseudo-random function PRF, and where Q is an authentication key owned by the second device and known to the candidate device provided the candidate device is a legitimate reloading device, and if the verification is positive, storing one or several reduced-coupon(s) provided by the candidate device in the second device. ### Claim 2 (depends on 1) The method according to claim 1, wherein said authentication key Q is equal to, or derived from, said regeneration key K. ### Claim 3 (depends on 1) The method according to claim 1, wherein said token T is transmitted by the second device to the candidate device. ### Claim 4 (depends on 3) The method according to claim 3, wherein said token T is generated by a counter located in said second device. ### Claim 5 (depends on 1) The method according to claim 1, wherein said token T is transmitted by the candidate device to the second device. ### Claim 6 (depends on 5) The method according to claim 5, wherein the second device is provided with a counter, and in that the second device checks that the value of the token T just received from the candidate device is strictly greater than the current counter value. ### Claim 7 (depends on 1) The method according to claim 1, wherein the current value and any necessary increments of token T are managed by a trusted central authority to which said legitimate reloading device and the second device can both get connected. ### Claim 8 (depends on 1) The method according to claim 1, wherein said token T results from the combination of a first number T1 and of a second number T2, and in that said second number T2 is transmitted by the candidate device to the second device. ### Claim 9 (depends on 8) The method according to claim 8, wherein said first number T1 is transmitted by the second device to the candidate device. ### Claim 10 (depends on 8) The method according to claim 8, wherein the current value and any necessary increments of said first number T1 are managed by a trusted central authority to which said legitimate reloading device and the second device can both get connected. ### Claim 11 An electronic circuit for consuming cryptographic reduced-coupons containing a processor and a memory, wherein a coupon comprises, a pseudo-random number ri=PRFK(i), where i is an index for labeling the coupon, PRF is a predetermined pseudo-random function and K is a regeneration key, and a “reduced-coupon” xi such that xi=ƒ(ri), where ƒ is a predetermined one-way function, said processor and said memory being arranged to: acquire a value of a token T using the processor, receive a verification value vT, verify whether said verification value vT is given by vT=PRF′Q(T), where Q is an authentication key and PRF′ is a predetermined keyed pseudo-random function identical to, or derived from, said pseudo-random function PRF, and receive and store one or several reduced-coupons in the electronic circuit, wherein a number of reduced-coupons xi that are pre-stored in the electronic circuit has reached a predetermined low amount. ### Claim 12 An Application Specific Integrated Circuit, comprising micro-components arranged to: acquire a value of a token T, receive a verification value vT, verify whether said verification value vT is given by vT=PRF′Q(T), where Q is an authentication key and PRF′ is a predetermined keyed pseudo-random function identical to, or derived from, said pseudo-random function PRF, said pseudo-random function being adapted to generate a pseudo-random number ri=PRFK(i), where K is a regeneration key, and i is an index for labeling a cryptographic coupon, said coupon comprising the pseudo-random number ri=PRFK(i), and, a “reduced-coupon” xi such that xi=ƒ(ri), where ƒ is a predetermined one-way function, and receive and store one or several reduced-coupons xi in the Application Specific Integrated Circuit, wherein a number of reduced-coupons xi that are pre-stored in the Application Specific Integrated Circuit has reached a predetermined low amount. ### Claim 13 (depends on 11) A portable device to exchange data with a terminal, said portable device comprising an electronic circuit according to claim 11, and said portable device also comprising a memory for storing the regeneration key K and the authentication key Q. ### Claim 14 (depends on 13) The portable device according to claim 13, wherein said portable device is an RFID tag. ### Claim 15 A terminal to exchange data with a portable device to provide it with reduced-coupons, wherein a coupon comprises, a pseudo-random number ri=PRFK(i), where i is an index for labeling a cryptographic coupon, PRF is a predetermined pseudo-random function, and K is a regeneration key, and a “reduced-coupon” xi such that xi=ƒ(ri), where ƒ is a predetermined one-way function, said terminal comprising a data processing device arranged to: acquire a value of a token T, generate a verification value vT is given by vT=PRF′Q(T), where PRF′ is a predetermined keyed pseudo-random function identical to, or derived from, said pseudo-random function PRF and where Q is an authentication key known to the terminal, transmit said verification value vT, generate a certain number of pseudo-random number ri, compute associated reduced-coupon xi, and transmit computed reduced-coupons to the portable device wherein a number of reduced-coupons xi that are pre-stored in the portable device has reached a predetermined low amount. ### Claim 16 (depends on 13) A system for cryptographic reduced-coupon reloading, comprising the portable device according to claim 13. ### Claim 17 (depends on 1) A non-transitory computer program product, comprising a computer usable medium having a computer readable program code embodied therein, said computer readable program code instructs a processor to execute the steps of the method according to claim 1. ### Claim 18 (depends on 12) A portable device to exchange data with a terminal, comprising an Application Specific Integrated Circuit according to claim 12, and said portable device also comprising a memory for storing the regeneration key K and the authentication key Q. ### Claim 19 (depends on 15) A system for cryptographic reduced-coupon reloading, comprising the terminal according to claim 15.