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We introduce HAIL (High-Availability and Integrity Layer), a distributed cryptographic system that allows a set of servers to prove to a client that a stored file is intact and retrievable. HAIL strengthens, formally unifies, and streamlines distinct approaches from the cryptographic and distributed-systems communities. Proofs in HAIL are efficiently(More)
A <i>proof of retrievability</i> (POR) is a compact proof by a file system (prover) to a client (verifier) that a target file <i>F</i> is intact, in the sense that the client can fully recover it. As PORs incur lower communication complexity than transmission of <i>F</i> itself, they are an attractive building block for high-assurance remote storage(More)
Infrastructure-as-a-system compute clouds such as Amazon's EC2 allow users to pay a flat hourly rate to run their virtual machine (VM) on a server providing some combination of CPU access, storage, and network. But not all VM instances are created equal: distinct underlying hardware differences, contention, and other phenomena can result in vastly differing(More)
This paper presents a new challenge--verifying that a remote server is storing a file in a fault-tolerant manner, i.e., such that it can survive hard-drive failures. We describe an approach called the Remote Assessment of Fault Tolerance (RAFT). The key technique in a RAFT is to measure the time taken for a server to respond to a read request for a(More)
Knowledge-based authentication systems generally rely upon users' explicit recollection of passwords, facts, or personal preferences. These systems impose a cognitive burden that often results in forgotten secrets or secrets with poor entropy. We propose an authentication system that instead draws on <i>implicit memory</i> - that is, the <i>unconscious</i>(More)
This work reduces the computational requirements of the additive noise steganalysis presented by Harmsen and Pearlman. The additive noise model assumes that the stegoimage is created by adding a pseudo-noise to a coverimage. This addition predictably alters the joint histogram of the image. In color images it has been shown that this alteration can be(More)
Assessing abnormal biomechanics when treating various lower extremity pathologies provides the athlete with comprehensive management and promotes injury prevention. However, there have been few previous investigations of abnormal biomechanical forces on ligamentous pathologies of the knee. During this clinical study we investigated the incidence of(More)
Plantar capsule-ligament sprain of the great toe metatarsophalangeal joint, herein referred to as "turf-toe," is discussed with emphasis on two apparantly predisposing factors, playing surface hardness and shoe stiffness. Surface hardness studies have previously been performed by the authors on natural grass and AstroTurf. A study of football shoe(More)
We propose a logic for specifying security policies at a very high level of abstraction. The logic accommodates the subjective nature of affirmations for authorization and knowledge without compromising the objective nature of logical inference. In order to accurately model consumable authorizations and resources, we construct our logic as a modal(More)
The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Abstract. Most cryptographic systems carry the basic assumption that entities are able to preserve the secrecy of their keys. With attacks today showing ever increasing sophistication, however, this tenet is eroding. " Advanced Persistent(More)