For small and midsize organizations, the outsourcing of demanding computational tasks to the cloud — huge banks of computers accessible over the Internet — can be much more cost-effective than buying their own hardware.
But it also poses a security risk: A malicious hacker could rent space on a cloud server and use it to launch programs that hijack legitimate applications, interfering with their execution.
In August, at the International Cryptology Conference, researchers from MIT and Israel's Technion and Tel Aviv University presented a new system that can quickly verify that a program running on the cloud is executing properly. That amounts to a guarantee that no malicious code is interfering with the program's execution.
The same system also protects the data used by applications running in the cloud, cryptographically ensuring that the user won't learn anything other than the immediate results of the requested computation. If, for instance, hospitals were pooling medical data in a huge database hosted on the cloud, researchers could look for patterns in the data without compromising patient privacy.
Although the paper reports new theoretical results, the researchers have also built working code that implements their system. At present, it works only with programs written in the C programming language, but adapting it to other languages should be straightforward.
The new work, like much current research on secure computation, requires that computer programs be represented as circuits. So the researchers' system includes a "circuit generator" that automatically converts C code to circuit diagrams. The circuits it produces, however, are much smaller than those produced by its predecessors, so by itself, the circuit generator may find other applications in cryptography.
Joining Chiesa on the paper are Madars Virza, also a graduate student in electrical engineering and computer science; the Technion's Daniel Genkin and Eli Ben-Sasson, who was a visiting professor at MIT for the past two years; and Tel Aviv University's Eran Tromer, who was a postdoc at MIT. The researchers' system implements a so-called zero-knowledge proof, a type of mathematical game invented by MIT professors Shafi Goldwasser and Silvio Micali and their colleague Charles Rackoff of the University of Toronto. In its cryptographic application, a zero-knowledge proof enables one of the game's players to prove to the other that he or she knows a secret key without actually divulging it.
But as its name implies, a zero-knowledge proof is a more general method for proving mathematical theorems — and the correct execution of a computer program can be redescribed as a theorem. So zero-knowledge proofs are by definition able to establish whether or not a computer program is executing correctly.
The problem is that existing implementations of zero-knowledge proofs — except in cases where they've been tailored to particular algorithms — take as long to execute as the programs they're trying to verify. That's fine for password verification, but not for a computation substantial enough that it might be farmed out to the cloud.
The researchers' innovation is a practical, succinct zero-knowledge proof for arbitrary programs. Indeed, it's so succinct that it can typically fit in a single data packet.Linear thinking
The problem, Virza says, is that "the current known constructions of the PCP theorem, though great in theory, have quite bad practical realizations." That's because the theory assumes that an adversary who's trying to produce a fraudulent proof has unbounded computational capacity. What Chiesa, Virza and their colleagues do instead is assume that the adversary is capable only of performing simple linear operations.
"This assumption is, of course, false in practice," Virza says. "So we use a cryptographic encoding to force the adversary to only linear evaluations. There is a way to encode numbers into such a form that you can add those numbers, but you can't do anything else. This is how we sidestep the inefficiencies of the PCP theorem."
Written by Larry Hardesty, MIT News Office
Andrew Carleen | EurekAlert!
Cutting edge research for the industries of tomorrow – DFKI and NICT expand cooperation
21.03.2017 | Deutsches Forschungszentrum für Künstliche Intelligenz GmbH, DFKI
Molecular motor-powered biocomputers
20.03.2017 | Technische Universität Dresden
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
23.03.2017 | Life Sciences
23.03.2017 | Power and Electrical Engineering
23.03.2017 | Earth Sciences