# US 7,472,274 B2 · Authentication of an electronic tag

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- Number: US 7,472,274 B2
- Document ID: US7472274B2
- Status: Granted
- Kind: B2
- Application number: 10/459,908
- Filed: 2003-06-12
- Published: 2003-12-18
- Granted: 2008-12-30
- Earliest claimed: 2002-06-13
- Assignees: STMicrolectronics S.A.
- Inventors: Christophe Moreaux; Claude Anguille
- Web page: https://patentgrep.com/patent/US7472274B2

## CPC

- G07F 7/1008: {Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system}
- G06Q 20/341: {Active cards, i.e. cards including their own processing means, e.g. including an IC or chip}
- G06Q 20/40975: {using encryption therefor}
- G07F 7/1016: {Devices or methods for securing the PIN and other transaction-data, e.g. by encryption (arrangements for secret communication, see H04L9/00)}
- H04L 9/3247: {involving digital signatures}
- G07F: COIN-FREED OR LIKE APPARATUS (coin sorting G07D3/00; coin testing G07D5/00; {handling coins or paper currencies apart from payment activated apparatus G07D; payment architectures, schemes or protocols G06Q20/00})
- G06Q: INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A method and a system for authenticating an electronic tag by a host communicating with this tag via a reader, including: calculating, on the tag side, a first digital signature using at least one first function shared by the tag and the reader, taking into account at least one first secret key known by the electronic tag and the reader only; transmitting the first signature to the reader; calculating, on the reader side, a second digital signal using at least one second function, different from the first function and shared by the reader and the host, taking the first signature into account; transmitting the second signature to the host; and checking, on the host side, the coherence between the second signature and a validation value calculated based on said second function and on a second secret key known by the host and by a single element selected from among the tag and the reader.

## Claims

### Claim 1

A method for authenticating an electronic tag by a host communicating with the electronic tag via a reader, the method comprising:
extracting from the electronic tag data to be transmitted to the host;
transmitting the data to the host via the reader, while storing the data on a host side and on a reader side;
generating, on the host side, a random or pseudo-random number and transmitting the random or pseudo-random number to the electronic tag via the reader, while storing the random or pseudo-random number on the host side, on the reader side, and on an electronic tag side;
calculating, on the electronic tag side, an intermediary signature by application of at least one first function shared by the electronic tag and the reader to the random or pseudo-random number, the data and at least one first secret key known by the electronic tag and the reader only;
calculating, on the electronic tag side, a first combination of XOR type of the intermediary signature with a second secret key, to obtain a first digital signature to be transmitted to the reader, wherein the second secret key is known by the electronic tag and the host only;
transmitting the first digital signature to the reader;
calculating, on the reader side, a second combination of XOR type of the received first digital signature with the intermediary value to obtain a result of the second combination;
calculating, on the reader side, a second signature by application of a second function to the result of the second combination, the random or pseudo-random number and the data, wherein the second function is a pseudo-random number generation function, common to the reader and to the host, and wherein the pseudo-random generation function uses as seeds the data, the random or pseudo-random number and, respectively on the reader side and on the host side, the second combination and the second secret key;
transmitting the second signature to the host; and
checking, on the host side, a coherence between the second signature and a validation value calculated from the second function and the second secret key.

### Claim 2 (depends on 1)

The method of claim 1, wherein the second secret key is stored in the electronic tag upon a first use of the electronic tag with the host.

### Claim 3 (depends on 1)

The method of claim 1, wherein the electronic tag is an electromagnetic transponder.

### Claim 4 (depends on 1)

An electronic tag, comprising an integrated circuit and means for storing a first secret key and for executing a first algorithmic function that implements the method of claim 1.

### Claim 5 (depends on 1)

A reader of an electronic tag, comprising an integrated circuit and means for implementing the method of claim 1.

### Claim 6 (depends on 1)

A microcontroller of authentication of an electronic tag, comprising an integrated circuit and means capable of implementing the method of claim 1 when it is desired to authenticate the electronic tag.