RASSLE: Return Address Stack based Side-channel LEakage

Microarchitectural attacks on computing systems often stem from simple artefacts in the underlying architecture. In this paper, we focus on the Return Address Stack (RAS), a small hardware stack present in modern processors to reduce the branch miss penalty by storing the return addresses of each function call. The RAS is useful to handle specifically the branch predictions for the RET instructions which are not accurately predicted by the typical branch prediction units. In particular, we envisage a spy process who crafts an overflow condition in the RAS by filling it with arbitrary return addresses, and wrestles with a concurrent process to establish a timing side channel between them. We call this attack principle, RASSLE 1 (Return Address Stack based Side-channel Leakage), which an adversary can launch on modern processors by first reverse engineering the RAS using a generic methodology exploiting the established timing channel. Subsequently, we show three concrete attack scenarios: i) How a spy can establish a covert channel with another co-residing process? ii) How RASSLE can be utilized to determine the secret key of the P-384 curves in OpenSSL (v1.1.1 library)? iii) How an Elliptic Curve Digital Signature Algorithm (ECDSA) secret key on P-256 curve of OpenSSL can be revealed using Lattice Attack on partially leaked nonces with the aid of RASSLE? In this attack, we show that the OpenSSL implementation of scalar multiplication on this curve has varying number of add-and-sub function calls, which depends on the secret scalar bits. We demonstrate through several experiments that the number of add-and-sub function calls can be used to template the secret bit, which can be picked up by the spy using the principles of RASSLE. Finally, we demonstrate a full end-to-end attack on OpenSSL ECDSA using curve parameters of curve P-256. In this part of our experiments with RASSLE, we abuse the deadline scheduler policy to attain perfect synchronization between the spy and victim, without any aid of induced synchronization from the victim code. This synchronization and timing leakage through RASSLE is sufficient to retrieve the Most Significant Bits (MSB) of the ephemeral nonces used while signature generation, from which we subsequently retrieve the secret signing key of the sender applying the Hidden Number Problem. 1RASSLE is a non-standard spelling for wrestle.

Digital environments as third spaces: analyses of simple artefacts in the rooms of the MOdE

With the spread of digital environments that allow the user to design and produce contents, we have asked ourselves whether digital museums can be considered as ‘third spaces’ in which it is possible to exhibit, research, aggregate and re-elaborate, in a shared narrative, materials and experiences coming from different contexts. Conceiving the digital museum as a third space of contamination between formal and informal, presence and distance, real and digital presupposes the rethinking of the functions of the museum itself, capable of connecting both the demands for safeguards and those of accessibility to the cultural heritage, for an access to knowledge that is increasingly open. Starting from these premises, this contribution references the digital museum Museo Officina dell’Educazione (MOdE) as a third space by specifically analysing the digital settings produced by students of the upper secondary schools and by university students.

4000 BCE: a cultural threshold

The archaeological evidence that has accumulated over the past five decades demonstrates that two very different situations existed successively in Britain in the centuries on either side of 4000 BCE. While this is in some ways an arbitrary date, it is nonetheless a convenient one, since there are very few indications that ‘Neolithic’ artefacts and structures existed in Britain for long before the turn of the fourth millennium. Up until 4000 BCE (or perhaps a century or two earlier), the mainland and islands were populated by people who were heavily dependent upon hunting and gathering; afterwards the population lived a way of life that to a greater or lesser extent relied on herding and cultivating. Further, whereas the technology of the hunting societies had been skilfully made but was highly portable, more durable artefacts and architecture now proliferated, creating a much denser world of crafted things. However, the available evidence can be cast in a number of different ways, with the material before and after the critical date being capable of sustaining either maximal or minimal interpretations. As a consequence, the ways in which the character and degree of change across the threshold can be understood are also multiple and varied. As we saw in Chapter 1, the archaeologists of the 1920s to 1960s emphasized the contrast between the Mesolithic and the Neolithic. Before the ‘transition’ between the two, Britain was home to a sparse population of hunter-foragers who followed game (including deer, wild pig, and wild cattle) and collected plants, nuts, and berries, and, for those near the sea, exploited marine resources. They had few, often simple artefacts, although it was acknowledged that significant skill was invested in some of them. They lived in informal campsites composed of rudimentary shelters while pursuing a transient way of life. Afterwards, in contrast, there were settled agriculturalists living in stable communities, in well-built houses, enjoying a mixed farming subsistence base. They were capable of building barrows and tombs for their dead, which may have demonstrated their incorporation into a widespread megalithic cult. The dichotomy between these two ways of life demanded that some fundamental change must have separated them, of whatever kind.

Inherited Social Difference at the Edges of Flakes

It is now generally accepted that there are no human societies which are truly egalitarian; this also true of bonobos and chimpanzees, among whom rank is inherited. If it were true of the common ancestor of Homo and Pan, there would have been (inherited) social inequality throughout our hominin ancestry. The problem is how to find it. It is also accepted that artefacts play an active and important role in our social lives; thus, socially defined differences may be reflected among the very simplest of artefacts. A case study of flaked stone from southwestern Egypt, dating to about 7000–8000 years ago, suggests that social differences can, indeed, be identified within very simple artefacts — in this case, plain, unmodified stone flakes. Using unmodified stone flakes, I explore the possibility of identifying not merely social difference but, specifically, inherited social difference in the Upper Palaeolithic of Europe and among early African hominins more than 2,000,000 years ago.