
Prof. Ninghui Li joined Purdue in August 2003 as an assistant professor in
Computer Sciences. His research interests are in computer security and
applied cryptography, e.g., security and privacy in distributed systems,
networks, databases, and electronic commerce, with a focus on access
control.
One focus of Prof. Li's work is on trust management, which is an approach to
access control in decentralized, open, and distributed systems. In trust
management, access control decisions are based on policy statements that
encode trust and delegation relationships among parties. He has designed,
together with Profs. John Mitchell and Will Winsborough, a family of
Role-Based Trust Management Languages. RT combines the strengths of
role-based access control (RBAC) and previous trust-management systems. He
also developed goal-directed algorithms to do efficient distributed
credential chain discovery, logic-based semantic foundations for security
policy languages, and algorithms and computational complexity
characterization for analyzing security properties such as safety and
availability when policies may change.
Professor Li is a co-PI of a recently-funded mid-size ITR project titled
"Automated Trust Negotiation in Open Systems". Automated Trust Negotiation
(ATN) is an approach to regulate the exchange of sensitive credentials by
using access-control policies. He has been working with Profs. Will
Winsborough and Kent Seamons on ATN, using the RT family of trust-management
languages. Together with Prof. Will Winsborough, he developed the Trust
Target Graph protocol for ATN.
Professor Li has also been working on applied cryptography. Together with
Profs. Dan Boneh and Wenliang Du, he introduced a cryptographic primitive
called oblivious signature-based envelope (OSBE). OSBE enables the sender
to send an encrypted message to the receiver such that the receiver can
decrypt if and only if it possesses the signature on a predetermined
message, yet the sender does not learn whether the receiver has the
signature or not. OSBE can be used in Automated Trust Negotiation to break
cyclic policy interdependency and can be applied to other privacy sensitive
scenarios. We developed an efficient and provably secure OSBE protocol for
credentials signed using RSA signatures and built one-round OSBE for Rabin
and BLS signatures from recent constructions for identity-based encryption.
Professor Li received a Ph.D. in Computer Science from New York University
in September 2000. Before joining Purdue, he was a research associate at
Computer Science Department, Stanford University. He has served on the
Program Committees of IEEE Computer Security Foundations Workshop and
International Conference on Trust Management, and has reviewed papers for a
number of international journals.