Physically Observable Cryptography

Abstract

Abstract. 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 complexitytheoretic 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.

Public-Key Encryption in the Bounded-Retrieval Model

“…In their seminal work, Micali and Reyzin [MR04] initiated the formal modeling of side-channel attacks under the axiom that "only computation leaks information", where each invocation of a cryptographic primitive leaks a function of only the bits accessed during that invocation. Several primitives have been constructed in this setting including stream ciphers [DP08,Pie09] and signatures [FKPR10].…”

Program Obfuscation with Leaky Hardware

“…In particular, our construction uses results of Goldwasser and Rothblum [24,22], which show how to convert circuits into ones that are secure in only computation leaks model of Micali and Reyzin [29] (or even in the stronger OCL + model described above).…”

“…The outline of our solution is as follows: Starting from any hardware-assisted obfuscation solution that uses a completely trusted device (e.g., [19,25]), we first transform that device into a system that resists leakage in the Micali-Reyzin model of "only computation leaks" (OCL) [29] (or actually in a slightly augmented OCL model). In principle, this can be done using OCL-compilers from the literature [27,24,22] (but see discussion in Section 1.4 about properties of these compilers).…”

Deterministic Public-Key Encryption Under Continual Leakage

“…In addition to constructions of randomized PKE mentioned above, leakage-resilient schemes for several tasks in a variety of leakage models are now known, e.g., digital signatures [LW10,BSW11,LLW11], identity-based encryption [BKKV10,CDRW10,LRW11], interactive proofs [GJS11,Pan14,AGP14], secure computation [FRR + 10, BGJK12,GR12], and so on. We remark that the study of leakage-resilient cryptography was initiated in [DP08,MR04,ISW03] as an attempt to provide an algorithmic defense against side-channel attacks [Koc96,AK97,QS01,OST06]. Renauld, Standaert, Veyrat-Charvillon, Kamel, and Flandre [RSV + 11] highlight several difficulties in formalizing an appropriate model of leakage for real-world side-channel attacks, and argue that often an algorithmic defense is not possible since the key might have been completely compromised.…”