3 research outputs found
SoK: Security of Cross-chain Bridges: Attack Surfaces, Defenses, and Open Problems
Cross-chain bridges are used to facilitate token and data exchanges across
blockchains. Although bridges are becoming increasingly popular, they are still
in their infancy and have been attacked multiple times recently, causing
significant financial loss. Although there are numerous reports online
explaining each of the incidents on cross-chain bridges, they are scattered
over the Internet, and there is no work that analyzes the security landscape of
cross-chain bridges in a holistic manner. To fill the gap, in this paper, we
performed a systematic study of cross-chain bridge security issues. First, we
summarize the characteristics of existing cross-chain bridges, including their
usages, verification mechanisms, communication models, and three
categorizations. Based on these characteristics, we identify 12 potential
attack vectors that attackers may exploit. Next, we introduce a taxonomy that
categorizes cross-chain attacks in the past two years into 10 distinct types,
and then provide explanations for each vulnerability type, accompanied by
Solidity code examples. We also discuss existing and potential defenses, as
well as open questions and future research directions on cross-chain bridges.
We believe that this systematization can shed light on designing and
implementing cross-chain bridges with higher security and, more importantly,
facilitating future research on building a better cross-chain bridge ecosystem
Predictions for the Dynamical States of the Didymos System before and after the Planned DART Impact
NASA's Double Asteroid Redirection Test (DART) spacecraft is planned to impact the natural satellite of (65803) Didymos, Dimorphos, around 23:14 UTC on 26 September 2022, causing a reduction in its orbital period that will be measurable with ground-based observations. This test of kinetic impactor technology will provide the first estimate of the momentum transfer enhancement factor at a realistic scale, wherein ejecta from the impact provides an additional deflection to the target. Earth-based observations, the LICIACube spacecraft (to be detached from DART prior to impact), and ESA's follow-up Hera mission to launch in 2024, will provide additional characterization of the deflection test. Together Hera and DART comprise the Asteroid Impact and Deflection Assessment (AIDA) cooperation between NASA and ESA. Here the predicted dynamical states of the binary system upon arrival and after impact are presented. The assumed dynamically relaxed state of the system will be excited by the impact, leading to an increase in eccentricity and slight tilt of the orbit together with enhanced libration of Dimorphos with amplitude dependent on the currently poorly known target shape. Free rotation around the moon's long axis may also be triggered and the orbital period will experience variations from seconds to minutes over timescales of days to months. Shape change of either body due to cratering or mass wasting triggered by crater formation and ejecta may affect but can be constrained through additional measurements. Both BYORP and gravity tides may cause measurable orbital changes on the timescale of Hera's rendezvous