GTACS

Abstract: Succinct non-interactive arguments (or SNARGs) are
computationally sound proofs whose communication complexity is
polylogarithmic the instance and witness sizes. Unfortunately, we
currently do not know of any construction of SNARGs with a formal
proof of security under any simple assumption. My talk will give a
broad black-box separation result, showing that the security of SNARGs
cannot be proven via a black-box reduction from any falsifiable
cryptographic assumption. This includes essentially all common

A secret-sharing scheme is a method by which a dealer distributes shares to parties such that only authorized subsets of parties can reconstruct the secret. Secret-sharing schemes are an important tool in cryptography and they are used as a building box in many secure protocols, e.g., general protocol for multiparty computation, Byzantine agreement, threshold cryptography, access control, attribute-based encryption, and generalized oblivious transfer.

We present overview of several of our recent results on practical attacks on the core Internet protocols: TCP, IP, DNS and HTTP. Our attacks are all by off-path spoofing adversary, i.e., do not require eavesdropping abilities. The attacks can be abused in many ways, including threats to integrity and confidentiality (e.g., via injection of malicious scripts/applets into web pages, for XSS, CSRF and phishing attacks, or via DNS poisoning), as well as for devastating Denial of Service (DoS) attacks.

Abstract:
A time-lock puzzle is a mechanism for sending messages ``to the future''. The sender publishes a puzzle whose solution is the message to be sent, thus hiding it until enough time has elapsed for the puzzle to be solved. For time-lock puzzles to be useful, generating a puzzle should take less time than solving it. Since adversaries may have access to many more computers than honest solvers, massively parallel solvers should not be able to produce a solution much faster than serial ones.

ABSTRACT: The traditional approach to formalizing ideal-model based definitions of security for multi-party protocols model adversaries (both real and ideal) as centralized entities that control all parties that deviate from the protocol. While this centralized-adversary modeling suffices for capturing basic security properties such as secrecy of local inputs and correctness of outputs against coordinated attacks, it turns out to be inadequate for capturing security properties that involve restricting the sharing of information between separate adversarial entities.

We consider multiparty computation (MPC) within a setting where a malicious adversary may corrupt some parties and {\it leak} information about the secret state of all honest parties. Leakage queries are chosen adaptively, throughout the protocol execution.

We show two main results.

We present a new framework for proving fully black-box
separations and lower bounds. We prove a general theorem that facilitates
the proofs of fully black-box lower bounds from a one-way function (OWF).

Speaker: Alessandro Chiesa (MIT CSAIL)
Time: Thursday August 9nd 2012, 14:00
Place: Schreiber 309, Tel Aviv University

Title: Fast Reductions from RAMs to
Delegatable Succinct Constraint Satisfaction Problems

Speaker: Alessandro Chiesa (MIT CSAIL)
Time: Thursday August 2nd 2012, 14:00
Place: Schreiber 309, Tel Aviv University

Title: How MIPs and Proof-Carrying Data Make Delegation More Affordable

Abstract:
In this talk, we will discuss two important efficiency aspects of succinct arguments:
(1) the time and space complexity of the prover
(2) the offline complexity of the verifier (a.k.a. preprocessing complexity)

New Directions in Cyber Security: Achieving Cyber Attack Tolerant Missions and Business Processes