Smart Certificates: Extending X.509 for Secure Attribute Service on the Web October 1999 Joon S. Park, Ph.D. Center for Computer High Assurance Systems Naval Research Laboratory

Abstract n In this paper, we have –identified the models for secure attribute services on the Web –developed n smart certificates based on X.509 –introduced n Possible applications of smart certificates

Introduction n WWW (World Wide Web) –synthesizes diverse technologies and components in Web environments –widely used for electronic commerce and business –mostly, Web servers use identity-based access control n scalability problem

Background n An attribute –a particular property of an entity n e.g., role, group, clearance, etc. n If attributes are provided securely, –Web servers can use those attributes n e.g., authentication, authorization, access control, electronic commerce, etc. n A successful marriage of the Web and secure attribute services is required

User-Pull Model

n Each user –pulls appropriate attributes from the Attribute Server –presents attributes and authentication information to Web servers n Each Web server –requires both identification and attributes from users n No new connections for the same attributes

Server-Pull Model

n Each user –presents only authentication information to Web servers n Each Web server –pulls users attributes from the Attribute Server n Authentication information and attribute do not go together n More convenient for users n Less convenient for Web servers

X.509 Certificate n Digitally signed by a certificate authority to confirm the information in the certificate belongs to the holder of the corresponding private key n support security on the Web based on PKI n standard n simply, bind users to keys n have the ability to be extended n Certificate Revocation List (CRL)

n Contents –version, serial number, subject, validity period, issuer, optional fields (v2) –subjects public key and algorithm info. –extension fields (v3) –digital signature of CA X.509 Certificate

Smart Certificates n Short-Lived Lifetime –More secure n typical validity period for X.509 is months (years) n the longer-lived certificates have a higher probability of being attacked –users may leave copies of the corresponding keys behind –No Certificate Revocation List (CRL) n supports simple and less expensive PKI

Smart Certificates n Containing Attributes Securely –Web servers can use secure attributes for their purposes –Each authority has independent control on the corresponding information n basic certificate (containing identity information) n each attribute can be added, changed, revoked, or re-issued by the appropriate authority –e.g., role, credit card numbers, clearance, etc.

Separate CAs in a Certificate

Smart Certificates n Postdated/Renewable Certificates –The certificate becomes valid at some time in the future n It is possible to make a smart certificate valid for a set of duration –The certificate can be renewed until the renewable time n a user keeps renewing it for shorter period n no need for CRL

n Confidentiality –Sensitive information can be n encrypted in smart certificates –e.g. passwords, credit card numbers, etc. Smart Certificates

Applications of Smart Certificates n On-Duty Control n Compatible with X.509 n User Authentication n Electronic Transaction n Pay-per-Access n Eliminating Single-Point Failure n Attribute-based Access Control

Conclusions n In this paper, we have –identified the models for secure attribute services on the Web –developed n smart certificates based on X.509 –introduced n Possible applications of smart certificates

A Smart Certificate