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Title: The design and analysis of real-world cryptographic protocols
Author: Scott, Samuel
ISNI:       0000 0004 8500 0869
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2018
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Designing cryptographic protocols for use in the real world is a challenging task, requiring a fine balance between practicality and security. Ad hoc constructions are often catastrophically broken, and even well-studied protocols regularly do not stand up to the test of time. We look at some of the ways cryptographic protocols are designed and analysed, applying these techniques to a variety of real-word scenarios. Our first scenario considers password storage, introducing a new primitive called a verifiable, partially oblivious PRF. We analyse the suitability of this primitive to the application in question, provide formal security proofs, and evaluate an example instantiation. The second scenario introduces a new security model to better understand the domain of key rotation for authenticated encryption. This is an area highly relevant to modern practices of storing data encrypted in the cloud. By introducing this new security model, we show that existing solutions fall short of achieving any meaningful security properties, and suggest some simple fixes. Finally, we implement and prove a new construction which meets our strongest definition, and analyse its practicality. Finally, to contrast with the computational approach in previous chapters, we additionally consider symbolic approaches to security analysis, using the formal verification tool Tamarin to prove security properties of the latest draft of the TLS 1.3 specification. Our results show formal method complement other approaches nicely, and provide a new perspective.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Cryptography ; Protocol analysis ; Provable Security