Fuzzy Identity Based Encryption

Brent WatersCurrent Research with Amit Sahai

Brent Waters Cryptographic Protocols for Memex 2

An Emergency Medical Appointment

•Record visit, test results, etc.

•Encryption

•No portable device requirement (can’t carry RSA public key)

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Use Identity Based Encryption (IBE)

My key is

“Aaron Smith”

Public Key is an identifier string (e.g.“aaron@princeton.edu”)

Use global public parameters

Master secret holder(s) can give out private keys to an individual that authenticates themselves

Boneh and Franklin ‘01

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Problems with Standard IBE

What should the identities be?• Names are not unique• Don’t necessarily want to tie to SS#, Driver’s License…

First time users• Don’t have identities yet

Certifying oneself to authority can be troublesome• Need documentation, etc.

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Biometric as an Identity

<0110010…00111010010>

Biometric stays with human

Should be unique (depends on quality of biometric)

Have identity before registration

Certification is natural

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Biometric as an Identity

<0110010…00111010010>

Biometric measure changes a little each time

•Environment

•Difference in Sensors

•Small change in trait

Cannot use a biometric as an identity in current IBE schemes

<0110110…00111010110><0100010…00111010110>

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Fuzzy Identity Based Encryption

A secret key for ID can decrypt a ciphertext encrypted with ID’ iff Hamming Distance(ID,ID’) d

M<0110010…00111010010>

<0100110…00111010110>

Private Key for IDEncrypted with ID’

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Fuzzy Identity Based Encryption

A secret key for ID can decrypt a ciphertext encrypted with ID’ iff Hamming Distance(ID,ID’) d

<0110010…00111010010>

<0010110…00011110110>

Private Key for IDEncrypted with ID’

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Final points

The biometric input is a public key, not a secret

Work is available on e-print and www.cs.princeton.edu/~bwaters/publications