### Abstract

As pervasive computing environments become popular, RFID devices, such as contactless smart cards and RFID tags, are introduced into our daily life. However, there exists a privacy problem that a third party can trace user's behavior by linking device's ID. The concept of unlinkability, that a third party cannot recognize whether some outputs are from the same user, is important to solve the privacy problem. A scheme using hash function satisfies unlinkability against a third party by changing the outputs of RFID devices every time. However, the schemes are not scalable since the server needs O(N) hash calculations for every ID matching, where N is the number of RFID devices. In this paper, we propose the K-steps ID matching scheme, which can reduce the number of the hash calculations on the server to O(log N). Secondly, we propose a quantification of unlinkability using conditional entropy and mutual information. Finally, we analyze the K-steps ID matching scheme using the proposed quantification, and show the relation between the time complexity and unlinkability.

Original language | English |
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Title of host publication | WPES'05: Proceedings of the 2005 ACM Workshop on Privacy in the Electronic Society |

Pages | 55-60 |

Number of pages | 6 |

Publication status | Published - 2005 |

Event | WPES'05: 2005 ACM Workshop on Privacy in the Electronic Society - Alexandria, VA, United States Duration: Nov 7 2005 → Nov 7 2005 |

### Other

Other | WPES'05: 2005 ACM Workshop on Privacy in the Electronic Society |
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Country | United States |

City | Alexandria, VA |

Period | 11/7/05 → 11/7/05 |

### Fingerprint

### All Science Journal Classification (ASJC) codes

- Engineering(all)

### Cite this

*WPES'05: Proceedings of the 2005 ACM Workshop on Privacy in the Electronic Society*(pp. 55-60)

**Quantitative evaluation of unlinkable ID matching schemes.** / Nohara, Yasunobu; Inoue, Sozo; Baba, Kensuke; Yasuura, Hiroto.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*WPES'05: Proceedings of the 2005 ACM Workshop on Privacy in the Electronic Society.*pp. 55-60, WPES'05: 2005 ACM Workshop on Privacy in the Electronic Society, Alexandria, VA, United States, 11/7/05.

}

TY - GEN

T1 - Quantitative evaluation of unlinkable ID matching schemes

AU - Nohara, Yasunobu

AU - Inoue, Sozo

AU - Baba, Kensuke

AU - Yasuura, Hiroto

PY - 2005

Y1 - 2005

N2 - As pervasive computing environments become popular, RFID devices, such as contactless smart cards and RFID tags, are introduced into our daily life. However, there exists a privacy problem that a third party can trace user's behavior by linking device's ID. The concept of unlinkability, that a third party cannot recognize whether some outputs are from the same user, is important to solve the privacy problem. A scheme using hash function satisfies unlinkability against a third party by changing the outputs of RFID devices every time. However, the schemes are not scalable since the server needs O(N) hash calculations for every ID matching, where N is the number of RFID devices. In this paper, we propose the K-steps ID matching scheme, which can reduce the number of the hash calculations on the server to O(log N). Secondly, we propose a quantification of unlinkability using conditional entropy and mutual information. Finally, we analyze the K-steps ID matching scheme using the proposed quantification, and show the relation between the time complexity and unlinkability.

AB - As pervasive computing environments become popular, RFID devices, such as contactless smart cards and RFID tags, are introduced into our daily life. However, there exists a privacy problem that a third party can trace user's behavior by linking device's ID. The concept of unlinkability, that a third party cannot recognize whether some outputs are from the same user, is important to solve the privacy problem. A scheme using hash function satisfies unlinkability against a third party by changing the outputs of RFID devices every time. However, the schemes are not scalable since the server needs O(N) hash calculations for every ID matching, where N is the number of RFID devices. In this paper, we propose the K-steps ID matching scheme, which can reduce the number of the hash calculations on the server to O(log N). Secondly, we propose a quantification of unlinkability using conditional entropy and mutual information. Finally, we analyze the K-steps ID matching scheme using the proposed quantification, and show the relation between the time complexity and unlinkability.

UR - http://www.scopus.com/inward/record.url?scp=33749005411&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33749005411&partnerID=8YFLogxK

M3 - Conference contribution

SN - 1595932283

SN - 9781595932280

SP - 55

EP - 60

BT - WPES'05: Proceedings of the 2005 ACM Workshop on Privacy in the Electronic Society

ER -