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Adi Shamir

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

22 papers
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22

NeurIPS Conference 2024 Conference Paper

MALT Powers Up Adversarial Attacks

  • Odelia Melamed
  • Gilad Yehudai
  • Adi Shamir

Current adversarial attacks for multi-class classifiers choose potential adversarial target classes naively based on the classifier's confidence levels. We present a novel adversarial targeting method, \textit{MALT - Mesoscopic Almost Linearity Targeting}, based on local almost linearity assumptions. Our attack wins over the current state of the art AutoAttack on the standard benchmark datasets CIFAR-100 and Imagenet and for different robust models. In particular, our attack uses a \emph{five times faster} attack strategy than AutoAttack's while successfully matching AutoAttack's successes and attacking additional samples that were previously out of reach. We additionally prove formally and demonstrate empirically that our targeting method, although inspired by linear predictors, also applies to non-linear models.

I&C Journal 2001 Journal Article

Guaranteeing the Diversity of Number Generators

  • Adi Shamir
  • Boaz Tsaban

A major problem in using iterative number generators of the form x i =f(x i−1) is that they can enter unexpectedly short cycles. This is hard to analyze when the generator is designed, hard to detect in real time when the generator is used, and can have devastating cryptanalytic implications. In this paper we define a measure of security, called sequence diversity, which generalizes the notion of cycle-length for noniterative generators. We then introduce the class of counter-assisted generators and show how to turn any iterative generator (even a bad one designed or seeded by an adversary) into a counter-assisted generator with a provably high diversity, without reducing the quality of generators which are already cryptographically strong.

FOCS Conference 1991 Conference Paper

Fully Parallelized Multi Prover Protocols for NEXP-Time (Extended Abstract)

  • Dror Lapidot
  • Adi Shamir

A major open problem in the theory of multiprover protocols is to characterize the languages which can be accepted by fully parallelized protocols which achieve an exponentially low probability of cheating in a single round. The problem was motivated by the observation that the probability of cheating the n parallel executions of a multiprover protocol can be exponentially higher than the probability of cheating in n sequential executions of the same protocol. The problem is solved by proving that any language in NEXP-time has a fully parallelized multiprover protocol. By combining this result with a fully parallelized version of the protocol of M. Ben-Or et al. (ACM Symp. on Theory of Computing, 1988), a one-round perfect zero-knowledge protocol (under no cryptographic assumptions) can be obtained for every NEXPTIME language. >

FOCS Conference 1990 Conference Paper

IP=PSPACE

  • Adi Shamir

It is proved that, when both randomization and interaction are allowed, the proofs that can be verified in polynomial time are exactly those proofs that can be generated with polynomial space. The interactive proofs introduced use only public coins, are accepted with probability one when the prover is honest, require only logarithmic workspace when the verifier is given a two-way access to his or her random tape, and by the use of known techniques can be turned into zero-knowledge proofs under the sole assumption that one-way functions exist. >

FOCS Conference 1990 Conference Paper

Multiple Non-Interactive Zero Knowledge Proofs Based on a Single Random String (Extended Abstract)

  • Uriel Feige
  • Dror Lapidot
  • Adi Shamir

The authors solve the two major open problems associated with noninteractive zero-knowledge proofs: how to enable polynomially many provers to prove in writing polynomially many theorems based on the basis of a single random string, and how to construct such proofs under general (rather than number-theoretic) assumptions. The constructions can be used in cryptographic applications in which the prover is restricted to polynomial time, and they are much simpler than earlier (and less capable) proposals. >

FOCS Conference 1989 Conference Paper

Planning and Learning in Permutation Groups

  • Amos Fiat
  • Shahar Moses
  • Adi Shamir
  • Ilan Shimshoni
  • Gábor Tardos

Planning is defined as the problem of synthesizing a desired behavior from given basic operations, and learning is defined as the dual problem of analyzing a given behavior to determine the unknown basic operations. Algorithms for solving these problems in the context of invertible operations on finite-state environments are developed. In addition to their obvious artificial intelligence applications, the algorithms can efficiently find the shortest way to solve Rubik's cube, test ping-pong protocols, and solve systems of equations over permutation groups. >

STOC Conference 1987 Conference Paper

Zero Knowledge Proofs of Identity

  • Uriel Feige
  • Amos Fiat
  • Adi Shamir

In this paper we extend the notion of zero knowledge proofs of membership (which reveal one bit of information) to zero knowledge proofs of knowledge (which reveal no information whatsoever). After formally defining this notion, we show its relevance to identification schemes, in which parties prove their identity by demonstrating their knowledge rather than by proving the validity of assertions. We describe a novel scheme which is provably secure if factoring is difficult and whose practical implementations are about two orders of magnitude faster than RSA-based identification schemes. In the last part of the paper we consider the question of sequential versus parallel executions of zero knowledge protocols, define a new notion of “transferable information”, and prove that the parallel version of our identification scheme (which is not known to be zero knowledge) is secure since it reveals no transferable information.

STOC Conference 1985 Conference Paper

The Cryptographic Security of Truncated Linearly Related Variables

  • Johan Håstad
  • Adi Shamir

In this paper we describe a polynomial time algorithm for computing the values of variables x 1 , … x k when some of their bits and some linear relationships between them are known. The algorithm is essentially optimal in its use of information in the sense that it can be applied as soon as the values of the x i become uniquely determined by the constraints. Its cryptanalytic significance is demonstrated by two applications: breaking linear congruential generators whose outputs are truncated, and breaking Blum's protocol for exchanging secrets.

STOC Conference 1984 Conference Paper

An Efficient Signature Scheme Based on Quadratic Equations

  • H. Ong
  • Claus-Peter Schnorr
  • Adi Shamir

Electronic messages, documents and checks must be authenticated by digital signatures which are not forgeable even by their recipients. The RSA system can generate and verify such signatures, but each message requires hundreds of high precision modular multiplications which can be implemented efficiently only on special purpose hardware. In this paper we propose a new signature scheme which can be easily implemented in software on microprocessors: signature generation requires one modular multiplication and one modular division, signature verification requires three modular multiplications, and the key size is comparable to that of the RSA system. The new scheme is based on the quadratic equation m = s 2 1 + ks 2 2 (mod n), where m is the message, s 1 and s 2 are the signature, and k and n are the publicly known key. While we cannot prove that the security of the scheme is equivalent to factoring, all the known methods for solving this quadratic equation for arbitrary k require the extraction of square roots modulo n or the solution of similar problems which are at least as hard as factoring. A novel property of the new scheme is that legitimate users can choose k in such a way that they can sign messages even without knowing the factorization of n, and thus everyone can use the same modulus if no one knows its factorization.

FOCS Conference 1984 Conference Paper

Polymorphic Arrays: A Novel VLSI Layout for Systolic Computers

  • Amos Fiat
  • Adi Shamir

This paper proposes a novel architecture for massively parallel systolic computers, which is based on results from lattice theory. In the proposed architecture, each processor is connected to four other processors via constant-lenght wires in an regular borderless pattern. The mapping of processes to processors is continuous, and the architecture guarantees exceptional load uniformity for rectangular process arrays of arbitrary sizes. In addition, no timesharing is ever required when the ration of processes to processors is smaller than 1//spl radic/5.

STOC Conference 1983 Conference Paper

On the Cryptographic Security of Single RSA Bits

  • Michael Ben-Or
  • Benny Chor
  • Adi Shamir

The ability to “hide” one bit in trapdoor functions has recently gained much interest in cryptography research, and is of great importance in many transactions protocols. In this paper we study the cryptographic security of RSA bits. In particular, we show that unless the cryptanalyst can completely break the RSA encryption, any heuristic he uses to determine the least significant bit of the cleartext must have an error probability greater than 1/4—ε A similar result is shown for Rabin's encryption scheme.

STOC Conference 1982 Conference Paper

How to Reuse a "Write-Once" Memory (Preliminary Version)

  • Ronald L. Rivest
  • Adi Shamir

Storage media such as digital optical disks, PROMS, or paper tape consist of a number of “write-once” bit positions ( wits ); each wit initially contains a “0” that may later be irreversibly overwritten with a “I”. We demonstrate that such “write-once memories” ( woms ) can be “rewritten” to a surprising degree. For example, only 3 wits suffice to represent any 2-bit value in a way that can later be updated to represent any other 2-bit value. For large k, 1.29... k wits suffice to represent a k -bit value in a way that can be similarly updated. Most surprising, allowing t writes of a k -bit value requires only t + o ( t ) wits, for any fixed k . For fixed t, approximately k.t /log( t ) wits are required as k → @@@@. An n -wit WOM is shown to have a “capacity” (i.e. k.t when writing a k -bit value t times) of up to n .log( n ) bits.

FOCS Conference 1979 Conference Paper

A T S^2 = O(2^n) Time/Space Tradeoff for Certain NP-Complete Problems

  • Richard Schroeppel
  • Adi Shamir

In this paper we develop a general purpose algorithm that can solve a number of NP-complete problems in time T = O(2n/2) and space S = O(2n/4). The algorithm can be generalized to a family of algorithms whose time and space complexities are related by T·S2 = O(2n). The problems it can handle are characterized by a few decomposition axioms, and they include knapsack problems, exact satisfiability problems, set covering problems, etc. The new algorithm has a considerable cryptanalytic significance, since it can break the Merkle-Hellman public key cryptosystem whose recommended size is n = 100.

TCS Journal 1978 Journal Article

The convergence of functions to fixedpoints of recursive definitions

  • Zohar Manna
  • Adi Shamir

The classical method for constructing the least fixedpoint of a recursive definition is to generate a sequence of functions whose initial element is the totally undefined function and which converges to the desired least fixedpoint. This method, due to Kleene, cannot be generalized to allow the construction of other fixedpoints. In this paper we present an alternate definition of convergence and a new fixedpoint access method of generating sequences of functions for a given recursive definition. The initial function of the sequence can be an arbitrary function, and the sequence will always converge to a fixedpoint that is “close” to the initial function. This defines a monotonic mapping from the set of partial functions onto the set of all fixedpoints of the given recursive definition.

FOCS Conference 1975 Conference Paper

On the Complexity of Timetable and Multi-Commodity Flow Problems

  • Shimon Even
  • Alon Itai
  • Adi Shamir

A very primitive version of Gotlieb's timetable problem is shown to be NP-complete, and therefore all the common timetable problems are NP-complete. A polynomial time algorithm, in case all teachers are binary, is shown. The theorem that a meeting function always exists if all teachers and classes have no time constraints is proved. The multi-commodity integral flow problem is shown to be NP-complete even if the number of commodities is two. This is true both in the directed and undirected cases. Finally, the two commodity real flow problem in undirected graphs is shown to be solvable in polynomial time. The time bound is O(|v|2|E|).

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