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Using Digital Credentials On The World-Wide Web. M. Winslett. Introduction. Problem Statement Traditional approaches for authenticating users is not enough to determine different types of users and their authorization to use services.
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Using Digital Credentials On The World-Wide Web M. Winslett
Introduction • Problem Statement • Traditional approaches for authenticating users is not enough to determine different types of users and their authorization to use services. • Internet is an open environment, identity does not give enough information about the authorization of users • Users may not want to reveal their identity if the service does not necessarily relevant with the identity.
Example Case • Access to ACM SIGMOD web site? • A shared username-password pair for all users • Little protection: How to prevent former users? What happens if the users spread password to others? • A username-password pair for each user • Administrative overhead • Hard to control authorization • Strong relation with user identity: Privacy lose • SSL authentication facilities • SSL specific identity. • Not a portable ID with the user (smartcard?) • Revealing browser identity which is irrelevant with access control decisions
Digital Credentials • Give each ACM SIGMOD member a digital credential issued (signed) by ACM or a trusted party (Verisign). • However, server and client software should agree on digital credentials and how they will be handled (authorization?).
Personal Security Assistant • Obtain, store digital credentials and policies • Negotiates with the server to decide which credentials are necessary • Attaches credentials to service requests according to client/server policies • May archive the credentials (including old ones)
Server Security Assistant • Store digital credentials and policies • Send server policy information and credentials to the client • Handle client credentials and credential acceptance policies • Assign roles to the users according to credentials • Cache credentials if necessary
Credentials • A digital credential does not need to store information about user’s real life identity • Example: ACM SIGMOD digital credential does not need to store the name of user. • Issuer can use local names or public keys of users in digital credentials
Credentials • Server can challenge the user to verify that he is the user that he is claiming (using PKCS) • To reduce the risk of disclosure of the information in digital credentials by the server, the client may request some credentials from server.
Policies • Server presents a policy to the client to explain what it needs for authorization • Client may present own policy that explains what and how it can disclose credentials to the server. • Server and Client may not want to reveal whole policy information in one step (step-by-step verification)
Trust Negotiation • Interactions to setup a trust relationship between client and server is called as trust negotiation. • Client and Server policies, credentials • Client and Server’s agreement on the contents of credentials • Need for a common language for policies and credentials • Authorization and role assignments
Trust Negotiation • Categorizing services (to avoid unnecessary amount of policy creation) • Handling complex situations in credentials and policies (e.g. expiry dates, situations that may not be enforceable) • Scalability
Supporting Structured Credentials and Sensitive Policies through Interoperable Strategies for Automated Trust Negotiation M. Winslett
Ideas • Strategy: An ordering of credential disclosures to access a resource (or a service). • Between client and server, different strategies may be used. • However, the strategies should implement a common basic protocol (TrustBuilder protocol).
Private and Trusted Interactions Bharat Bhargava
Ideas • Formulate trust gain with respect to privacy loss • Self descriptiveness • Apoptosis (Clean self-destruction) • Proximity-based evaporation
Summary • The language to define policies and credentials is very important in trust negotiation • A common protocol for trust negotiation is necessary, but different strategies can be used. • Scalability, manageability of the protocols are important. Less human interaction is very important. • Privacy loss should be a major concern during trust negotiation.