Attack surface | EPFL Graph Search

The attack surface of a software environment is the sum of the different points (for "attack vectors") where an unauthorized user (the "attacker") can try to enter data to, extract data, control a device or critical software in an environment. Keeping the attack surface as small as possible is a basic security measure. Elements of an attack surface Worldwide digital change has accelerated the size, scope, and composition of an organization's attack surface. The size of an attack surface may fluctuate over time, adding and subtracting assets and digital systems (e.g. websites, hosts, cloud and mobile apps, etc). Attack surface sizes can change rapidly as well. Digital assets eschew the physical requirements of traditional network devices, servers, data centers, and on-premise networks. This leads to attack surfaces changing rapidly, based on the organization's needs and the availability of digital services to accomplish it. Attack surface scope also varies from organizat

Attacks on some post-quantum cryptographic protocols: The case of the Legendre PRF and SIKE

Novak Kaluderovic

Post-quantum cryptography is a branch of cryptography which deals with cryptographic algorithms whose hardness assumptions are not based on problems known to be solvable by a quantum computer, such as the RSA problem, factoring or discrete logarithms.This thesis treats two such algorithms and provides theoretical and practical attacks against them.The first protocol is the generalised Legendre pseudorandom function - a random bit generator computed as the Legendre symbol of the evaluation of a secret polynomial at an element of a finite field. We introduce a new point of view on the protocol by analysing the action of the group of Möbius transformations on the set of secret keys (secret polynomials).We provide a key extraction attack by creating a table which is cubic in the number of the function queries, an improvement over the previous algorithms which only provided a quadratic yield. Furthermore we provide an ever stronger attack for a new set of particularly weak keys.The second protocol that we cover is SIKE - supersingular isogeny key encapsulation.In 2017 the American National Institute of Standards and Technology (NIST) opened a call for standardisation of post-quantum cryptographic algorithms. One of the candidates, currently listed as an alternative key encapsulation candidate in the third round of the standardisation process, is SIKE.We provide three practical side-channel attacks on the 32-bit ARM Cortex-M4 implementation of SIKE.The first attack targets the elliptic curve scalar multiplication, implemented as a three-point ladder in SIKE. The lack of coordinate randomisation is observed, and used to attack the ladder by means of a differential power analysis algorithm.This allows us to extract the full secret key of the target party with only one power trace.The second attack assumes coordinate randomisation is implemented and provides a zero-value attack - the target party is forced to compute the field element zero, which cannot be protected by randomisation. In particular we target both the three-point ladder and isogeny computation in two separate attacks by providing maliciously generated public keys made of elliptic curve points of irregular order.We show that an order-checking countermeasure is effective, but comes at a price of 10% computational overhead. Furthermore we show how to modify the implementation so that it can be protected from all zero-value attacks, i.e., a zero-value is never computed during the execution of the algorithm.Finally, the last attack targets a point swapping procedure which is a subroutine of the three-point ladder. The attack successfully extracts the full secret key with only one power trace even if the implementation is protected with coordinate randomisation or order-checking. We provide an effective countermeasure --- an improved point swapping algorithm which protects the implementation from our attack.

EPFL2022

A Note on a Privacy-Preserving Distance-Bounding Protocol

Jean-Philippe Aumasson, Aikaterini Mitrokotsa

Distance bounding protocols enable a device to establish an upper bound on the physical distance to a communication partner so as to prevent location spoofing, as exploited by relay attacks. Recently, Rasmussen and Cˇapkun (ACM-CCS’08) observed that these protocols leak information on the location of the parties to external observers, which is undesirable in a number of applications—for example if the leaked information leads to the identification of the parties among a group of devices. To remedy this problem, these authors proposed a “privacy-preserving” distance bounding protocol, i.e. that leaks no information on the location of the parties. The present paper reports results from an in-depth security analysis of that new protocol, with as main result an attack that recovers the ephemeral secrets as well as the location information of the two parties for particular choices of parameters. Overall, our results do not contradict the preliminary security analysis by the designers, but rather extends it to other parts of the attack surface.

Springer2011

Secure Neighbor Discovery and Ranging in Wireless Networks

Marcin Poturalski

This thesis addresses the security of two fundamental elements of wireless networking: neighbor discovery and ranging. Neighbor discovery consists in discovering devices available for direct communication or in physical proximity. Ranging, or distance bounding, consists in measuring the distance between devices, or providing an upper bound on this distance. Both elements serve as building blocks for a variety of services and applications, notably routing, physical access control, tracking and localization. However, the open nature of wireless networks makes it easy to abuse neighbor discovery and ranging, and thereby compromise overlying services and applications. To prevent this, numerous works proposed protocols that secure these building blocks. But two aspects crucial for the security of such protocols have received relatively little attention: formal verification and attacks on the physical-communication-layer. They are precisely the focus of this thesis. In the first part of the thesis, we contribute a formal analysis of secure communication neighbor discovery protocols. We build a formal model that captures salient characteristics of wireless systems such as node location, message propagation time and link variability, and we provide a specification of secure communication neighbor discovery. Then, we derive an impossibility result for a general class of protocols we term "time-based protocols", stating that no such protocol can provide secure communication neighbor discovery. We also identify the conditions under which the impossibility result is lifted. We then prove that specific protocols in the time-based class (under additional conditions) and specific protocols in a class we term "time- and location-based protocols," satisfy the neighbor discovery specification. We reinforce these results by mechanizing the model and the proofs in the theorem prover Isabelle. In the second part of the thesis, we explore physical-communication-layer attacks that can seemingly decrease the message arrival time without modifying its content. Thus, they can circumvent time-based neighbor discovery protocols and distance bounding protocols. (Indeed, they violate the assumptions necessary to prove protocol correctness in the first part of the thesis.) We focus on Impulse Radio Ultra-Wideband, a physical layer technology particularly well suited for implementing distance bounding, thanks to its ability to perform accurate indoor ranging. First, we adapt physical layer attacks reported in prior work to IEEE 802.15.4a, the de facto standard for Impulse Radio, and evaluate their performance. We show that an adversary can achieve a distance-decrease of up to hundreds of meters with an arbitrarily high probability of success, with only a minor cost in terms of transmission power (few dB). Next, we demonstrate a new attack vector that disrupts time-of-arrival estimation algorithms, in particular those designed to be precise. The distance-decrease achievable by this attack vector is in the order of the channel spread (order of 10 meters in indoor environments). This attack vector can be used in previously reported physical layer attacks, but it also creates a new type of external attack based on malicious interference. We demonstrate that variants of the malicious interference attack are much easier to mount than the previously reported external attack. We also provide design guidelines for modulation schemes and devise receiver algorithms that mitigate physical layer attacks. These countermeasures allow the system designer to trade off security, ranging precision and cost in terms of transmission power and packet length.