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Biometrics and SIM May 24, 2009

Posted by tcarlyle in Biometrics, identity management, SIM Cards.

I know I said I would not post so soon, but here it goes a small post on Biometrics (reusing the text from my thesis =D)


Biometrics corresponds to the recognition of an individual based on the measurement and analysis of his physical and behavioral aspects. Some biometric techniques include: fingerprint, iris scan, face recognition, DNA, hand geometry, voice recognition and hand-writing patterns. The biometric information can enhance identity, verification and authentication mechanisms as it consists into a unique feature that can identify a user. 


In fact biometrics is massively deployed in the several physical identity cards that carry a picture of the owner. This picture, a facial biometric, is aimed to present something that can be used for a visual verification on the side of the agent.


One of the biggest concerns about the usage of biometric information is the case where the biometric template, the synthesis of the biometric characteristics, is stolen. Since the biometric template can’t be revoked, a user can’t revoke his fingerprint or have his iris reissued, this is a very important topic to be taken into account. A solution for that is the storage of the fingerprint information in a secure environment, such as a smart card. It enables the possibility of employing match-on-card (MOC) identification without the need of transmitting the biometric information outside of the card. Inside the card, the biometric information can serve as one of the authentication factors complementing or replacing passwords. 


Despite MOC solutions on the regular smart cards, for example the Portuguese e-ID, there are already deployments on the SIM Card. As shown in the article”Beefing up security with biometrics” from Card Technology Today, May, 2008, the memory needed to store the biometric information is not so high, specially if you take into account the new high-density smart cards. A facial image can require 20KB while the iris image can require 30KB and a fingerprint 8KB. If instead of using the image, the biometric template is used, the size requirements are reduced by around 90% or less. 


What security experts such as Bruce Schneier and Steve Riley discuss is that biometrics should not be used as an authentication secret, but as identity information. By that, the identity, biometric data publicly known, identifies the user, but in order to obtain authorization in a system, a secret is used. This argument is based on the fact that biometrics can be tampered: they can be scanned, they are left when people touch objects, people can be filmed without their consent. Moreover, differently from the secret, the biometric can’t be revoked.


The MOC solution in the smart card mentioned before has the biometric in a context that is hard to characterize between identity or authorization secret. It is something in between, since the biometric information is actually the input to authenticate the person which has the card, but the biometric alone is powerless and the card can be revoked. I woud say that it is secure enough for most of the day-to-day purposes since it combines “what you are” with “what you have” and it can be revoked.  It seems harder once it is easier to steal (or guess) a password than a fingerprint(hopefully not your finger as in those sci-fi  action movies) . 

If you have any comments around the MOC security, please write. I’ll consider them when revising the thesis =)


1. First day of Nordsec 09 « Thomas Carlyle’s tech blog - October 15, 2009

[…] his speech was not characterized if it was for identification or authentication as I mentioned in a post in the blog, it generated a lot of questions around the dangers of impersonating someone using a copy of the […]

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