Results 1  10
of
15
Fully LeakageResilient Signatures
, 2010
"... A signature scheme is fully leakage resilient (Katz and Vaikuntanathan, ASIACRYPT ’09) if it is existentially unforgeable under an adaptive chosenmessage attack even in a setting where an adversary may obtain bounded (yet arbitrary) leakage information on all intermediate values that are used throu ..."
Abstract

Cited by 23 (3 self)
 Add to MetaCart
A signature scheme is fully leakage resilient (Katz and Vaikuntanathan, ASIACRYPT ’09) if it is existentially unforgeable under an adaptive chosenmessage attack even in a setting where an adversary may obtain bounded (yet arbitrary) leakage information on all intermediate values that are used throughout the lifetime of the system. This is a strong and meaningful notion of security that captures a wide range of sidechannel attacks. One of the main challenges in constructing fully leakageresilient signature schemes is dealing with leakage that may depend on the random bits used by the signing algorithm, and constructions of such schemes are known only in the randomoracle model. Moreover, even in the randomoracle model, known schemes are only resilient to leakage of less than half the length of their signing key. In this paper we construct the first fully leakageresilient signature schemes without random oracles. We present a scheme that is resilient to any leakage of length (1 − o(1))L bits, where L is the length of the signing key. Our approach relies on generic cryptographic primitives, and at the same time admits rather efficient instantiations based on specific numbertheoretic
Tamper and Leakage Resilience in the SplitState Model
, 2011
"... It is notoriously difficult to create hardware that is immune from side channel and tampering attacks. A lot of recent literature, therefore, has instead considered algorithmic defenses from such attacks. In this paper, we show how to algorithmically secure any cryptographic functionality from conti ..."
Abstract

Cited by 18 (3 self)
 Add to MetaCart
(Show Context)
It is notoriously difficult to create hardware that is immune from side channel and tampering attacks. A lot of recent literature, therefore, has instead considered algorithmic defenses from such attacks. In this paper, we show how to algorithmically secure any cryptographic functionality from continual splitstate leakage and tampering attacks. A splitstate attack on cryptographic hardware is one that targets separate parts of the hardware separately. Our construction does not require the hardware to have access to randomness. On contrast, prior work on protecting from continual combined leakage and tampering [KKS11] required true randomness for each update. Our construction is in the common reference string (CRS) model; the CRS must be hardwired into the device. We note that prior negative results show that it is impossible to algorithmically secure a cryptographic functionality against a combination of arbitrary continual leakage and tampering attacks without true randomness; therefore restricting our attention to the splitstate model is justified. Our construction is simple and modular, and relies on a new construction, in the CRS model, of nonmalleable codes with respect to splitstate tampering functions, which may be of independent interest. 1
Faust.: LeakageResilient Cryptography from the InnerProduct Extractor
 ASIACRYPT2011, LNCS 7073
, 2011
"... Abstract. We present a generic method to secure various widelyused cryptosystems against arbitrary sidechannel leakage, as long as the leakage adheres three restrictions: first, it is bounded per observation but in total can be arbitrary large. Second, memory parts leak independently, and, third, ..."
Abstract

Cited by 16 (2 self)
 Add to MetaCart
Abstract. We present a generic method to secure various widelyused cryptosystems against arbitrary sidechannel leakage, as long as the leakage adheres three restrictions: first, it is bounded per observation but in total can be arbitrary large. Second, memory parts leak independently, and, third, the randomness that is used for certain operations comes from a simple (nonuniform) distribution. As a fundamental building block, we construct a scheme to store a cryptographic secret such that it remains information theoretically hidden, even given arbitrary continuous leakage from the storage. To this end, we use a randomized encoding and develop a method to securely refresh these encodings even in the presence of leakage. We then show that our encoding scheme exhibits an efficient additive homomorphism which can be used to protect important cryptographic tasks such as identification, signing and encryption. More precisely, we propose efficient implementations of the Okamoto identification scheme, and of an ElGamalbased cryptosystem with security against continuous leakage, as long as the leakage adheres the above mentioned restrictions. We prove security of the Okamoto scheme under the DL assumption and CCA2 security of our encryption scheme under the DDH assumption.
LeakageResilient Cryptography from Minimal Assumptions
, 2012
"... We present new constructions of leakageresilient cryptosystems, which remain provably secure even if the attacker learns some arbitrary partial information about their internal secret key. For any polynomial ℓ, we can instantiate these schemes so as to tolerate up to ℓ bits of leakage. While there ..."
Abstract

Cited by 8 (1 self)
 Add to MetaCart
We present new constructions of leakageresilient cryptosystems, which remain provably secure even if the attacker learns some arbitrary partial information about their internal secret key. For any polynomial ℓ, we can instantiate these schemes so as to tolerate up to ℓ bits of leakage. While there has been much prior work constructing such leakageresilient cryptosystems under concrete numbertheoretic and algebraic assumptions, we present the first schemes under general and minimal assumptions. In particular, we construct: • Leakageresilient publickey encryption from any standard publickey encryption. • Leakageresilient weak pseudorandom functions, symmetrickey encryption, and messageauthentication codes from any oneway function. These are the first constructions of leakageresilient symmetrickey primitives that do not rely on publickey assumptions. We also get the first constructions of leakageresilient publickey encryption from “search assumptions”, such as the hardness of factoring or CDH. Although our schemes can tolerate arbitrarily large amounts of leakage, the tolerated rate of leakage (defined as the ratio of leakageamount to keysize) is rather poor in comparison to prior results under specific assumptions. As a building block of independent interest, we study a notion of weak hashproof systems in the publickey and symmetrickey settings. While these inherit some of the interesting security properties of standard hashproof systems, we can instantiate them under general assumptions.
BiTR: Builtin Tamper Resilience
"... Abstract. The assumption of the availability of tamperproof hardware tokens has been used extensively in the design of cryptographic primitives. For example, Katz (Eurocrypt 2007) suggests them as an alternative to other setup assumptions, towards achieving general UCsecure multiparty computation ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
(Show Context)
Abstract. The assumption of the availability of tamperproof hardware tokens has been used extensively in the design of cryptographic primitives. For example, Katz (Eurocrypt 2007) suggests them as an alternative to other setup assumptions, towards achieving general UCsecure multiparty computation. On the other hand, a lot of recent research has focused on protecting security of various cryptographic primitives against physical attacks such as leakage and tampering. In this paper we put forward the notion of Builtin Tamper Resilience (BiTR) for cryptographic protocols, capturing the idea that the protocol that is encapsulated in a hardware token is designed in such a way so that tampering gives no advantage to an adversary. Our definition is within the UC model, and can be viewed as unifying and extending several prior related works. We provide a composition theorem for BiTR security of protocols, impossibility results, as well as several BiTR constructions for specific cryptographic protocols or tampering function classes. In particular, we achieve general UCsecure computation based on a hardware token that may be susceptible to affine tampering attacks. We also prove that two existing identification and signature schemes (by Schnorr and Okamoto, respecitively) are already BiTR against affine attacks (without requiring any modification or endcoding). We next observe that nonmalleable codes can be used as state encodings to achieve the BiTR property, and show new positive results for deterministic nonmalleable encodings for various classes of tampering functions. 1
On continual leakage of discrete log representations. IACR Cryptology ePrint Archive, 2012:367, 2012. informal publication
 BB04a] [BB04b] [BF01] [BF03] [Bon98] [BPR+ 08] [CDK+ 12] [CHK03] [CHKP10] [Coc01] [CS98] [DHT12] [Gen06] [Gen09] Dan Boneh and
, 2004
"... Let G be a group of prime order q, and let g1,..., gn be random elements of G. We say that a vector x = (x1,..., xn) ∈ Zn q is a discrete log representation of some some element y ∈ G (with respect to g1,..., gn) if g x1 1 · · · gxn n = y. Any element y has many discrete log representations, form ..."
Abstract

Cited by 4 (0 self)
 Add to MetaCart
Let G be a group of prime order q, and let g1,..., gn be random elements of G. We say that a vector x = (x1,..., xn) ∈ Zn q is a discrete log representation of some some element y ∈ G (with respect to g1,..., gn) if g x1 1 · · · gxn n = y. Any element y has many discrete log representations, forming an affine subspace of Zn q. We show that these representations have a nice continuous leakageresilience property as follows. Assume some attacker A(g1,..., gn, y) can repeatedly learn L bits of information on arbitrarily many random representations of y. That is, A adaptively chooses polynomially many leakage functions fi: Zn q → {0, 1} L, and learns the value fi(xi), where xi is a fresh and random discrete log representation of y. A wins the game if it eventually outputs a valid discrete log representation x ∗ of y. We show that if the discrete log assumption holds in G, then no polynomially bounded A can win this game with nonnegligible probability, as long as the leakage on each representation is bounded by L ≈ (n − 2) log q = (1 − 2 n) · x.
LeakageResilient Zero Knowledge ∗
"... In this paper, we initiate a study of zero knowledge proof systems in the presence of sidechannel attacks. Specifically, we consider a setting where a cheating verifier is allowed to obtain arbitrary bounded leakage on the entire state (including the witness and the random coins) of the proverduring ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
In this paper, we initiate a study of zero knowledge proof systems in the presence of sidechannel attacks. Specifically, we consider a setting where a cheating verifier is allowed to obtain arbitrary bounded leakage on the entire state (including the witness and the random coins) of the proverduring the entire protocol execution. We formalize a meaningful definition of leakageresilient zero knowledge (LRZK) proof system, that intuitively guarantees that the protocol does not yield anything beyond the validity of the statement and the leakage obtained by the verifier. We give a construction of LRZK interactive proof system based on standard general assumptions. To the best of our knowledge, this is the first instance of a cryptographic interactive protocol where the adversary is allowed to perform leakage attacks during the protocol execution on the entire state of honest party (in contrast, prior work only considered leakage prior to the protocol execution, or very limited leakage during the protocol execution). Next, we give an LRNIZK proof system based on standard numbertheoretic assumptions. Finally, we demonstrate the usefulness of our notions by giving two concrete applications: • We initiate a new line of research to relax the assumption on the “tamperproofness ” of
Bilinear Entropy Expansion from the Decisional Linear Assumption
"... We develop a technique inspired by pseudorandom functions that allows us to increase the entropy available for proving the security of dual system encryption schemes under the Decisional Linear Assumption. We show an application of the tool to AttributeBased Encryption by presenting a KeyPolicy AB ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
We develop a technique inspired by pseudorandom functions that allows us to increase the entropy available for proving the security of dual system encryption schemes under the Decisional Linear Assumption. We show an application of the tool to AttributeBased Encryption by presenting a KeyPolicy ABE scheme that exhibits a significant improvement over the state of the art schemes in public parameter size in terms of the number of attributeuses allowed in the policy while remaining fully secure under the Decisional Linear Assumption. 1
Multiparty computation secure against continual memory leakage
 IN: STOC
, 2012
"... We construct a multiparty computation (MPC) protocol that is secure even if a malicious adversary, in addition to corrupting 1 fraction of all parties for an arbitrarily small constant > 0, can leak information about the secret state of each honest party. This leakage can be continuous for an u ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
We construct a multiparty computation (MPC) protocol that is secure even if a malicious adversary, in addition to corrupting 1 fraction of all parties for an arbitrarily small constant > 0, can leak information about the secret state of each honest party. This leakage can be continuous for an unbounded number of executions of the MPC protocol, computing different functions on the same or different set of inputs. We assume a (necessary) “leakfree ” preprocessing stage. We emphasize that we achieve leakage resilience without weakening the security guarantee of classical MPC. Namely, an adversary who is given leakage on honest parties ’ states, is guaranteed to learn nothing beyond the input and output values of corrupted parties. This is in contrast with previous works on leakage in the multiparty protocol setting, which weaken the security notion, and only guarantee that a protocol which leaks ` bits about the parties ’ secret states, yields at most ` bits of leakage on the parties ’ private inputs. For some functions, such as voting, such leakage can be detrimental. Our result relies on standard cryptographic assumptions, and our security parameter is polynomially related to the number of parties.
Deterministic PublicKey Encryption under Continual Leakage
, 2014
"... Deterministic publickey encryption, introduced by Bellare, Boldyreva, and O’Neill (CRYPTO 2007), is an important database encryption technique which allows quick, logarithmictime, search over encrypted data items. The technique is most effective in scenarios where frequent search queries are perfo ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
Deterministic publickey encryption, introduced by Bellare, Boldyreva, and O’Neill (CRYPTO 2007), is an important database encryption technique which allows quick, logarithmictime, search over encrypted data items. The technique is most effective in scenarios where frequent search queries are performed over a huge database of highly sensitive, yet unpredictable, data items such as credit card or social security numbers. Such databases, however, are also the ideal target for hackers since even partial data leaks may reveal significantly damaging information to the attacker. Motivated by the goal of limiting the damage in such scenarios, we apply the ideas from leakage resilient cryptography to deterministic publickey encryption (DPKE). We formulate appropriate security notions for DPKE in the presence of leakage, and present constructions that achieve them in the standard model. We work in the continual leakage model, where the secretkey is updated at regular intervals and an attacker can learn arbitrary but bounded leakage during each time interval. We, however, do not consider leakage during the updates. Our main construction is based on the (standard) linear assumption in bilinear groups, tolerating