Description
In the white-box attack context, i.e., the setting where an implementation of a cryptographic algorithm is executed on an untrusted open platform, the adversary has full access to the implementation and its execution environment. As a result, the adversary is much more powerful than in a traditional black-box environment in which the adversary has only access to the inputs and outputs of a cryptographic algorithm. For example, the adversary can make use of widely available tools such as disassemblers and debuggers with breakpoint functionality. An example of a white-box environment is a digital content protection system in which the client is implemented in software and executed on a PC, tablet, set-top box or a mobile phone. A malicious end-user may attempt to extract a secret key used for content decryption from the software. Next, the end-user may distribute this key to non-entitled end-users, or the end-user may use this key to decrypt the content directly, circumventing content usage rules. White-box cryptography aims to protect the confidentiality of the secret key of a cryptographic algorithm in a white-box environment. In particular, it is a technique to construct software implementations of a cryptographic algorithm that are sufficiently secure against a white-box attacker. These implementations are referred to as white-box implementations.<br/> In this talk, we elaborate on white-box cryptography in general (e.g., what are the main white-box security objectives and the typical attacker¿s goals in the white-box environment) and we discuss its application to AES. We start with the design of the first published white-box AES implementation by Chow et al. in 2002, and the efficient attack on this implementation by Billet et al. in 2004. Next, we discuss the design of two new white-box AES implementations claimed to be resistant against Billet et al.¿s attack, and we present practical attacks showing that none of these proposed countermeasures actually achieve white-box security. To conclude, we discuss a novel white-box technique proposed by Michiels and Gorissen in 2010 and share some thoughts about the future of white-box cryptography.
Next sessions
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Efficient zero-knowledge proofs and arguments in the CL framework
Speaker : Agathe Beaugrand - Institut de Mathématiques de Bordeaux
The CL encryption scheme, proposed in 2015 by Castagnos and Laguillaumie, is a linearly homomorphic encryption scheme, based on class groups of imaginary quadratic fields. The specificity of these groups is that their order is hard to compute, which means it can be considered unknown. This particularity, while being key in the security of the scheme, brings technical challenges in working with CL,[…] -
Constant-time lattice reduction for SQIsign
Speaker : Sina Schaeffler - IBM Research
SQIsign is an isogeny-based signature scheme which has recently advanced to round 2 of NIST's call for additional post-quantum signatures. A central operation in SQIsign is lattice reduction of special full-rank lattices in dimension 4. As these input lattices are secret, this computation must be protected against side-channel attacks. However, known lattice reduction algorithms like the famous[…] -
Circuit optimisation problems in the context of homomorphic encryption
Speaker : Sergiu Carpov - Arcium
Fully homomorphic encryption (FHE) is an encryption scheme that enables the direct execution of arbitrary computations on encrypted data. The first generation of FHE schemes began with Gentry's groundbreaking work in 2019. It relies on a technique called bootstrapping, which reduces noise in FHE ciphertexts. This construction theoretically enables the execution of any arithmetic circuit, but[…] -
Cycles of pairing-friendly abelian varieties
Speaker : Maria Corte-Real Santos - ENS Lyon
A promising avenue for realising scalable proof systems relies on the existence of 2-cycles of pairing-friendly elliptic curves. More specifically, such a cycle consists of two elliptic curves E/Fp and E’/Fq that both have a low embedding degree and also satisfy q = #E(Fp) and p = #E’(Fq). These constraints turn out to be rather restrictive; in the decade that has passed since 2-cycles were first[…]-
Cryptography
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