Guest lecture by
Helger Lipmaa
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Title
Accountable Certificate Management using Undeniable Attestations
Speaker
- Helger Lipmaa
- Helsinki University of Technology, Espoo, Finland
Time and Place
- Tuesday, September 26, 2000
- at 14.15
- Lecture Room A414 (4th floor), Department of Computer Science
Abstract
This presentation initiates a study of accountable certificate management
methods, necessary to support long-term authenticity of digital
documents. Our main contribution is a model for accountable certificate
management, where clients receive attestations confirming
inclusion/removal of their certificates from the database of valid
certificates. We explain why accountability depends on the inability of
the third parties to create contradictory attestations. After that we
define an undeniable attester as a primitive that provides efficient
attestation creation, publishing and verification, so that it is
intractable to create contradictory attestations. We introduce
authenticated search trees and build an efficient undeniable attester
upon them. The proposed system is the first accountable long-term
certificate management system. Moreover, authenticated search trees can
be used in many security-critical applications instead of the (sorted)
hash trees to reduce trust in the authorities, without decrease in
efficiency. Therefore, the undeniable attester promises looks like a
very useful cryptographic primitive with a wide range of applications.
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