Fresh Re-keying II: Securing Multiple Parties against Side-Channel and Fault Attacks

Abstract

Abstract. Security-aware embedded systems are widespread nowadays and many applications, such as payment, pay-TV and automotive applications rely on them. These devices are usually very resource constrained but at the same time likely to operate in a hostile environment. Thus, the implementation of low-cost protection mechanisms against physical attacks is vital for their market relevance. An appealing choice, to counteract a large family of physical attacks with one mechanism, seem to be protocol-level countermeasures. At last year's Africacrypt, a fresh re-keying scheme has been presented which combines the advantages of re-keying with those of classical countermeasures such as masking and hiding. The contribution of this paper is threefold: most importantly, the original fresh re-keying scheme was limited to one low-cost party (e.g. an RFID tag) in a two party communication scenario. In this paper we extend the scheme to n low-cost parties and show that the scheme is still secure. Second, one unanswered question in the original paper was the susceptibility of the scheme to algebraic SPA attacks. Therefore, we analyze this property of the scheme. Finally, we implemented the scheme on a common 8-bit microcontroller to show its efficiency in software.

On the Security of Fresh Re-keying to Counteract Side-Channel and Fault Attacks

“…In this paper, we show that the requirements for the key derivation function that have been formulated in [12,13] are not sufficient. In fact, we present a simple key-recovery attack on the fresh re-keying schemes proposed in [12,13]. The basic idea of the attack is that since the scheme changes the block cipher key for every encrypted message block, a time-memory trade-off strategy is possible.…”

“…Medwed et al provide several arguments for this in [12,13]. In fact, they argue that it is not necessary to have a cryptographic algorithm for the key derivation and propose to use a modular multiplication for the key derivation.…”

“…In [12,13], Medwed et al propose a re-keying scheme that prevents DPA and DFA attacks by preventing multiple executions of an algorithm with the same key. The basic idea of this re-keying scheme is to never use a long-term key k directly in a cryptographic algorithm, but to derive a fresh session key k * from k upon each invocation of the algorithm.…”

On Secure Embedded Token Design

“…For a given signal-to-noise ratio, this forces an attacker to develop more effective attacks rather than simply using more traces; when combined with conventional countermeasures, it can effectively prevent such attacks. One can view this process as playing a similar role to key refresh [18,17], but without the need for synchronization. In addition, we add the first secure authentication payload, HMAC [20], to the list of applications implemented as Yao circuits.…”

Towards fresh re-keying with leakage-resilient PRFs: cipher design principles and analysis

“…This means that reaching acceptable noise levels for the masking countermeasure to become effective requires additional shuffling, e.g. as proposed in [24] and leading to significant performance overheads (in the 10th of thousands cycles). These preliminary investigations suggest with good confidence that in a hardware context, the fresh re-keying based the construction we describe in this paper had good potential to lead to a better performance vs. security tradeoff than a masked modular multiplication.…”