Martínez-Silva et al.

On the Generation of X.509v3 Certificates

withBiometric Information

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Motivation

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Public Key Cryptography

• Conceptually, it was invented in 1976 by Diffie and Hellman.

• In 1977 (30 years ago!) RSA the first practical public key cryptosystem was invented.

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Public Key Cryptography

• Some major examples of public key cryptosystems are:

– RSA

– DSA

– ECC

– NTRU

• Although public key cryptography allows the definition of digital signatures and their verification in a reliable way, this mechanism is not enough for preventing attacks.

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Digital Certificate Benefits• Secure Key Authentication

– Avoids attacks such as man-in-the-middle

• Key Revocation

– A certificate indicates valid periods of operation

• Non-repudiation

– A user cannot deny his/her public key.

• Policy Applications

– It helps to concert security policies among a large community

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X.509v3 Certificate• X.509 certificates version 3, were defined as

an IETF standard [RFC2459, 1999].

• It is composed by three main structures: TBS certificate (TBSCertificate), algorithm identifier (signature-Algorithm) and digital signature (signatureValue).

• The TBS certificate and algorithm identifier consists of ten common fields, six of them mandatory and four optional.

• Additionally, an X.509v3 certificate must be formatted according to the (Abstract Syntax Notation One) ASN.1 language

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X.509 v3 Digital certificate

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Biometric Digital Certificate: Why?

• By incorporating biometric information, it allows a stronger and more robust authentication.

• For certain applications will be important to make sure that the biometric information presented to a system really belongs to a given user and that that biometric data has been certificated by an authority.

• Similarly, it may help to avoid that a user denies his biometric information

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Technical Contributions

we present the kernel implementation of a Mobile Certification Authority (MCA), with the following features:

• Our MCA kernel is able to issue digital certificates fully complying with the X.509v3 standard;

• it supports either RSA or ECDSA as a public key cryptosystem engine and;

• it can incorporate biometric-based user identification information (in the form of fingerprint recognition) to the digital certificate.

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Research Contributions

• We provide a performance comparison between RSA and elliptic curve cryptosystems as a public key crypto-engines.

• Among the NIST-recommended elliptic curves we establish which one is the more suitable for mobile devices such as PDAs.

• We assessed the space/bandwidth needed for a X.509v3 certificate with and without biometric information.

• We give a concrete example of a biometric ECC/RSA certificate fully complying with the X.509v3 standard.

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Generating/validating X.509v3 Certificates

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TBS Certificate Generation

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X.509v3 Certificate Generation.

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X.509v3 certificate Parsing

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X.509v3 certificate Verification

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Mobile Certification Authority

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Main Architecture

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Elliptic Curve Cryptography Library

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PDA Specification

HP iPAQ Pocket PC h5550

Operating System Windows Pocket PC'03

Processor Intel XScale @ 400MHz

Memory 128MB SDRAM;48MB ROM

Biometric Reader FingerChip technology with BioAPI Library

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PDA Application

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Experimental Results

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Biometric ECC X.509v3 Digital ASN.1

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Key Generation Timings

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Digital Signature/Verification Timings

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Certificates sizes comparison with and without biometric

information.

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Conclusions• fingerprint biometric information increases the

size of all certificates considered by about 1K byte, but there is room for improvements.

• A rather surprising result was that the size difference between the RSA-based and ECDSA-based digital certificates is fairly small.

• We confirmed that ECDSA is more efficient than RSA. Concretely, when working with constrained computational environments and/or wireless applications, the NIST-163K-ECDSA appears to be the ideal selection.