International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Silvio Micali

Publications

Year
Venue
Title
2020
CRYPTO
Our Models and Us 📺
Silvio Micali
2015
EPRINT
2014
TCC
2010
CRYPTO
2009
TCC
2008
TCC
2008
PKC
2006
EPRINT
Independent Zero-Knowledge Sets
Rosario Gennaro Silvio Micali
We define and construct Independent Zero-Knowledge Sets (ZKS) protocols. In a ZKS protocols, a Prover commits to a set $S$, and for any $x$, proves non-interactively to a Verifier if $x \in S$ or $x \notin S$ without revealing any other information about $S$. In the {\em independent} ZKS protocols we introduce, the adversary is prevented from successfully correlate her set to the one of a honest prover. Our notion of independence in particular implies that the resulting ZKS protocol is non-malleable. On the way to this result we define the notion of {\em independence} for commitment schemes. It is shown that this notion implies non-malleability, and we argue that this new notion has the potential to simplify the design and security proof of non-malleable commitment schemes. Efficient implementations of ZKS protocols are based on the notion of mercurial commitments. Our efficient constructions of independent ZKS protocols requires the design of {\em new} commitment schemes that are simultaneously independent (and thus non-malleable) and mercurial.
2005
TCC
2005
TCC
2004
EUROCRYPT
2004
TCC
2004
TCC
2003
CRYPTO
2003
EPRINT
Sequential Aggregate Signatures from Trapdoor Permutations
An aggregate signature scheme (recently proposed by Boneh, Gentry, Lynn and Shacham) is a method for combining $n$ signatures from $n$ different signers on $n$ different messages into one signature of unit length. We propose \emph{sequential aggregate signatures}, in which the set of signers is ordered. The aggregate signature is computed by having each signer, in turn, add his signature to it. We show how to realize this in such a way that the size of the aggregate signature is independent of $n$. This makes sequential aggregate signatures a natural primitive for certificate chains, whose length can be reduced by aggregating all signatures in a chain. We give a construction based on families of certified trapdoor permutations, and show how to instantiate our scheme based on RSA.
2003
EPRINT
Physically Observable Cryptography
Silvio Micali Leonid Reyzin
Complexity-theoretic cryptography considers only abstract notions of computation, and hence cannot protect against attacks that exploit the information leakage (via electromagnetic fields, power consumption, etc.) inherent in the physical execution of any cryptographic algorithm. Such "physical observation attacks" bypass the impressive barrier of mathematical security erected so far, and successfully break mathematically impregnable systems. The great practicality and the inherent availability of physical attacks threaten the very relevance of complexity-theoretic security. To respond to the present crisis, we put forward physically observable cryptography: a powerful, comprehensive, and precise model for defining and delivering cryptographic security against an adversary that has access to information leaked from the physical execution of cryptographic algorithms. Our general model allows for a variety of adversaries. In this paper, however, we focus on the strongest possible adversary, so as to capture what is cryptographically possible in the worst possible, physically observable setting. In particular, we -- consider an adversary that has full (and indeed adaptive) access to any leaked information; -- show that some of the basic theorems and intuitions of traditional cryptography no longer hold in a physically observable setting; and -- construct pseudorandom generators that are provably secure against all physical-observation attacks. Our model makes it easy to meaningfully restrict the power of our general physically observing adversary. Such restrictions may enable schemes that are more efficient or rely on weaker assumptions, while retaining security against meaningful physical observations attacks.
2002
JOFC
2001
ASIACRYPT
2001
CRYPTO
2001
EUROCRYPT
2001
EUROCRYPT
2001
EUROCRYPT
Zero Knowledge Has Come of Age
Silvio Micali
2000
CRYPTO
2000
EUROCRYPT
2000
EPRINT
Identification Protocols Secure Against Reset Attacks
We provide identification protocols that are secure even when the adversary can reset the internal state and/or randomization source of the user identifying itself, and when executed in an asynchronous environment like the Internet that gives the adversary concurrent access to instances of the user. These protocols are suitable for use by devices (like smartcards) which when under adversary control may not be able to reliably maintain their internal state between invocations.
1999
CRYPTO
1999
EUROCRYPT
1999
EUROCRYPT
1999
EPRINT
Improving the Exact Security of Digital Signature Schemes
Silvio Micali Leonid Reyzin
We provide two contributions to exact security analysis of digital signatures: We put forward a new method of constructing Fiat-Shamir-like signature schemes that yields better "exact security" than the original Fiat-Shamir method; and we extend exact security analysis to "exact cost-security analysis" by showing that digital signature schemes with "loose security" may be preferable for reasonable measures of cost.
1999
EPRINT
Resettable Zero-Knowledge
We introduce the notion of Resettable Zero-Knowledge (rZK), a new security measure for cryptographic protocols which strengthens the classical notion of zero-knowledge. In essence, an rZK protocol is one that remains zero knowledge even if an adeversary can interact with the prover many times, each time resetting the prover to its initial state and forcing him to use the same random tape. Under general complexity asumptions, which hold for example if the Discrete Logarithm Problem is hard, we construct (1) rZK proof-systems for NP: (2) constant-round resettable witness-indistinguishable proof-systems for NP; and (3) constant-round rZK arguments for NP in the public key model where verifiers have fixed, public keys associated with them. In addition to shedding new light on what makes zero knowledge possible (by constructing ZK protocols that use randomness in a dramatically weaker way than before), rZK has great relevance to applications. Firstly, we show that rZK protocols are closed under parallel and concurrent execution and thus are guaranteed to be secure when implemented in fully asynchronous networks, even if an adversary schedules the arrival of every message sent. Secondly, rZK protocols enlarge the range of physical ways in which provers of a ZK protocols can be securely implemented, including devices which cannot reliably toss coins on line, nor keep state betweeen invocations. (For instance, because ordinary smart cards with secure hardware are resattable, they could not be used to implement securely the provers of classical ZK protocols, but can now be used to implement securely the provers of rZK protocols.)
1998
EPRINT
More on Proofs of Knowledge
Shai Halevi Silvio Micali
The notion of proofs of knowledge is central to cryptographic protocols, and many definitions for it have been proposed. In this work we explore a different facet of this notion, not addressed by prior definitions. Specifically, prior definitions concentrate on capturing the properties of the verifier, and do not pay much attention to the properties of the prover. Our new definition is strictly stronger than previous ones, and captures new and desirable properties. In particular, it guarantees prover feasibility, that is, it guarantees that the time spent by the prover in a proof of knowledge is comparable to that it spends in an "extraction" of this knowledge. Our definition also enables one to consider meaningfully the case of a single, specific prover.
1996
CRYPTO
1996
JOFC
1996
JOFC
1995
CRYPTO
1995
EUROCRYPT
1994
EUROCRYPT
(title unknown)
Silvio Micali
1993
CRYPTO
1992
CRYPTO
1991
CRYPTO
1991
JOFC
1990
CRYPTO
1989
CRYPTO
1989
CRYPTO
1989
CRYPTO
1989
CRYPTO
1988
CRYPTO
1988
CRYPTO
1988
CRYPTO
1988
CRYPTO
1988
CRYPTO
1988
CRYPTO
1987
CRYPTO
1986
CRYPTO
1986
CRYPTO
1984
CRYPTO
1984
CRYPTO
1982
CRYPTO