Rita Alexandra Rodrigues Prates

Co-advisor: M. Pupo Correia

Proof of Timely-Retrievability for Storage Systems at the Edge

Tese submetida para provas de mestrado em Engenharia Informática e de Computadores Instituto Superior Técnico, Universidade de Lisboa.


Edge computing is a model that places servers close to the edge of the network, in order to assist applications that run in resource-constrained devices. Edge servers may be used to store files such that clients can access data with low-latency. Yet, as the capacity of edge nodes is limited, providers of edge storage may be tempted to oversell their capacity and to hide this behavior by fetching, on-demand, data from the cloud instead of serving it with the required low latency.

In this thesis, we study techniques that have been proposed in the literature that can help in detect- ing this type of misbehavior, and design and implement a new proof of storage to detect this rational behavior. Our Proof of Timely-Retrievability (PoTR) aims to assess whether a storage node at the edge is able to retrieve a data object with a latency smaller than some specified threshold delta. We leverage the availability of Trusted Execution Environments (TEEs), more precisely Intel SGX, to ensure that the proof is produced by the fog node being audited and to reduce the communication between the auditor and the audited node. Our proof is issued in response to a challenge: we describe how a challenge may be designed and configured, so that a PoTR is obtained. We have evaluated our design experimentally, and we show that the auditor is able to distinguish a fog node that respects the target limit on data access latency delta from a fog node that does not.


Proof of Timely-Retrievability for Storage Systems at the Edge
Rita Alexandra Rodrigues Prates
MSc Thesis. Instituto Superior Técnico, Universidade de Lisboa.
November 2021.
Available BibTeX, MSC Thesis, and extended abstract, and mid-term report.
Prova de Resposta Pontual no Acesso ao Armazenamento Contratado na Periferia da Rede.
R. Prates, C. Correia, M. Correia, and L. Rodrigues
Actas do décimo segundo Simpósio de Informática (Inforum), Lisboa, Portugal, Sep. 2021.
Available BibTeX, extended report (pdf).

Luís Rodrigues