000217903 001__ 217903
000217903 005__ 20190619023706.0
000217903 0247_ $$2doi$$a10.5075/epfl-thesis-6976
000217903 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis6976-3
000217903 02471 $$2nebis$$a10616883
000217903 037__ $$aTHESIS
000217903 041__ $$aeng
000217903 088__ $$a6976
000217903 245__ $$aTrustworthy Cloud Storage
000217903 269__ $$a2016
000217903 260__ $$bEPFL$$c2016$$aLausanne
000217903 300__ $$a118
000217903 336__ $$aTheses
000217903 502__ $$aProf. Mohammad Amin Shokrollahi (président) ; Prof. Arjen Lenstra (directeur de thèse) ; Prof. Bryan Ford, Dr Hugues Mercier, Prof. Pascal Junod (rapporteurs)
000217903 520__ $$aThe Cloud trend is an attempt to leverage economics of scale in the domain of computing resources. Unfortunately, this often means losing control of the lower levels of a computer system, and exposing users to new threat vectors. These threats may be significant enough to forbid the use of clouds, and force giving up on their economical advantages. Chapter 1 introduces some issues with current cloud storage systems, that should be fixed before a cloud storage system can be considered as safe as a self-managed system. Among these, we will focus on censorship resistance. We also explain the not immediately obvious way in which they relate to issues discussed in the two latter chapters. Chapter 2 formally defines censorship-resistance and describes the ST E P-archive, an abstract model for a generic class of censorship-resistant storage systems. Within this model, we expose an asymmetry in hardness between attack algorithms (trying to perform censorship) and defense algorithms (trying to repair censored files). We discuss ideal choices for the many parameters and derive useful mathematical bounds when possible. We also simulate the behaviour of an ideal storage system to obtain experimental evidence of the effect of these parameter choices. We show that this model exhibits several counter-intuitive properties. Chapter 3 deals with the issue of incorrect key generation. Cryptography being an essential component of our proposed secure storage system, we discuss common pitfalls in implemen- tations of popular asymmetric cryptographic algorithms, and evidence of their presence in real-world implementations. Chapter 4 discusses an operational aspect of storage systems, the choice of a block storage unit, and the consequences of lack thereof. In particular, it shows how the size of a ciphertext can act as a side channel and leak information about encrypted contents to an attacker, within the context of large media files distributed through public file sharing systems.
000217903 6531_ $$acensorship
000217903 6531_ $$acloud
000217903 6531_ $$acoding
000217903 6531_ $$acryptography
000217903 6531_ $$astorage
000217903 700__ $$0244291$$g145600$$aAugier, Maxime
000217903 720_2 $$aLenstra, Arjen$$edir.$$g171548$$0244290
000217903 8564_ $$uhttps://infoscience.epfl.ch/record/217903/files/EPFL_TH6976.pdf$$zn/a$$s3107954$$yn/a
000217903 909C0 $$xU11265$$0252286$$pLACAL
000217903 909CO $$pthesis-public$$pDOI$$pIC$$ooai:infoscience.tind.io:217903$$qGLOBAL_SET$$pthesis$$pthesis-bn2018$$qDOI2
000217903 917Z8 $$x108898
000217903 917Z8 $$x108898
000217903 917Z8 $$x108898
000217903 918__ $$dEDIC$$cIIF$$aIC
000217903 919__ $$aLACAL
000217903 920__ $$b2016$$a2016-4-7
000217903 970__ $$a6976/THESES
000217903 973__ $$sPUBLISHED$$aEPFL
000217903 980__ $$aTHESIS