We describe recent results obtained with AQUA, a mobile robot capable of swimming, walking and amphibious operation. Designed to rely primarily on visual sensors, the AQUA robot uses vision to navigate underwater using servobased guidance, and also to obtain high-resolution range scans of its local environment. This paper describes some of the pragmatic and logistic obstacles encountered, and provides an overview of some of the basic capabilities of the vehicle and its associated sensors. Moreover, this paper presents the first ever amphibious transition from walking to swimming.

Absbad -This paper describe an underwater walking mbotic system being developed under the name AQUA, the goals of the AQUA pmjecf the overall hardware and sofhvare design, the basic hardware and sensor packages that have heen developed, and some iaithl experiments. The mbat is based on the RHex hexapod mbot and usel B mite of sensing technologies, primarily based on computer vlrlon and INS, to allow it to naiigate and map clear shallow-water environments. The sensor-based navigation and mapping algorithms are based on the ore of both artincid floating visual m d aroustie inndmnrks BP well BE on naturally occurring uodemrter landmarks and trioocuhr stereo.

Abstract. Replay attacks are often the most costly attacks to thwart when dealing with off-chip memory integrity. With a trusted System-on-Chip, the existing countermeasures against replay require a large amount of on-chip memory to provide tamper-proof storage for metadata such as hash values or nonces. Tree-based strategies can be deployed to reduce this unacceptable overhead; for example, the well-known Merkle tree technique decreases this overhead to a single hash value. However, it comes at the cost of performancekilling characteristics for embedded systems -e.g. non-parallelizable hash computations on tree updates. In this paper, we propose an alternative solution: the Tamper-Evident Counter Tree (TEC-Tree). It allows for tamper-evident offchip storage of the nonces involved in a replay countermeasure; TEC-Tree parallelizes the computations involved in both the authentication and tree update processes. Moreover, because our tree relies on block encryption, it provides data confidentiality at no extra cost. TEC-Tree is a deployable solution for memory integrity, with low performance hit and hardware cost.