Cryptographic techniques for managing computational effort

Rangasamy, Jothi Ramalingam (2012) Cryptographic techniques for managing computational effort. PhD thesis, Queensland University of Technology.


Availability has become a primary goal of information security and is as significant as other goals, in particular, confidentiality and integrity. Maintaining availability of essential services on the public Internet is an increasingly difficult task in the presence of sophisticated attackers. Attackers may abuse limited computational resources of a service provider and thus managing computational costs is a key strategy for achieving the goal of availability. In this thesis we focus on cryptographic approaches for managing computational costs, in particular computational effort. We focus on two cryptographic techniques: computational puzzles in cryptographic protocols and secure outsourcing of cryptographic computations.

This thesis contributes to the area of cryptographic protocols in the following ways. First we propose the most efficient puzzle scheme based on modular exponentiations which, unlike previous schemes of the same type, involves only a few modular multiplications for solution verification; our scheme is provably secure.

We then introduce a new efficient gradual authentication protocol by integrating a puzzle into a specific signature scheme. Our software implementation results for the new authentication protocol show that our approach is more efficient and effective than the traditional RSA signature-based one and improves the DoSresilience of Secure Socket Layer (SSL) protocol, the most widely used security protocol on the Internet.

Our next contributions are related to capturing a specific property that enables secure outsourcing of cryptographic tasks in partial-decryption. We formally define the property of (non-trivial) public verifiability for general encryption schemes, key encapsulation mechanisms (KEMs), and hybrid encryption schemes, encompassing public-key, identity-based, and tag-based encryption avors. We show that some generic transformations and concrete constructions enjoy this property and then present a new public-key encryption (PKE) scheme having this property and proof of security under the standard assumptions.

Finally, we combine puzzles with PKE schemes for enabling delayed decryption in applications such as e-auctions and e-voting. For this we first introduce the notion of effort-release PKE (ER-PKE), encompassing the well-known timedrelease encryption and encapsulated key escrow techniques. We then present a security model for ER-PKE and a generic construction of ER-PKE complying with our security notion.

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ID Code: 61007
Item Type: QUT Thesis (PhD)
Supervisor: Boyd, Colin, Nieto, Juan Manuel Gonzalez, & Stebila, Douglas
Keywords: denial-of-service, denial-of-service resilience, cryptographic puzzles, time-lock puzzles, puzzle-unforgeability, puzzle-diculty, non-parallelisability, mutual authentication, bernstein's signatures, secure sockets layer (ssl), public-key encryptionript: , timed-release encryption, key encapsulation mechanism, data encapsulation mechanism, encapsulated key escrow, ciphertext indistinguishability under chosen plaintext attacks and adaptive chosen ciphertext attacks, random Oracle model, standard model
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Past > Institutes > Information Security Institute
Institution: Queensland University of Technology
Deposited On: 28 Jun 2013 03:48
Last Modified: 10 Sep 2015 02:28

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