Month: January 2020

Enlarge (credit: David Göthberg)

Three years ago, Ars declared the SHA1 cryptographic hash algorithm officially dead after researchers performed the world’s first known instance of a fatal exploit known as a "collision" on it. On Tuesday, the dead SHA1 horse got clobbered again as a different team of researchers unveiled a new attack that’s significantly more powerful.

The new collision gives attackers more options and flexibility than were available with the previous technique. It makes it practical to create PGP encryption keys that, when digitally signed using SHA1 algorithm, impersonate a chosen target. More generally, it produces the same hash for two or more attacker-chosen inputs by appending data to each of them. The attack unveiled on Tuesday also costs as little as $45,000 to carry out. The attack disclosed in 2017, by contrast, didn’t allow forgeries on specific predetermined document prefixes and was evaluated to cost from $110,000 to $560,000 on Amazon’s Web Services platform, depending on how quickly adversaries wanted to carry it out.

The new attack is significant. While SHA1 has been slowly phased out over the past five years, it remains far from being fully deprecated. It’s still the default hash function for certifying PGP keys in the legacy 1.4 version branch of GnuPG, the open-source successor to PGP application for encrypting email and files. Those SHA1-generated signatures were accepted by the modern GnuPG branch until recently, and were only rejected after the researchers behind the new collision privately reported their results.

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  This gallery highlights some of the high resolution images captured by the Chang'e spacecraft. [credit: CNSA ]

A little more than one year ago, China's Chang'e 4 spacecraft landed on the far side of the Moon. In doing so, it became the first-ever vehicle to make a soft landing on the side of the Moon facing away from Earth.

To mark the one-year anniversary, China released a batch of scientific data and images captured by five scientific payloads aboard the 1.2-ton spacecraft and its small Yutu 2 rover. Since the landing, the rover has driven a little more than 350 meters across the Moon's surface, studying rock formations and taking additional photos. The data was collected over a period of 12 lunar "days," or most of the last year.

The lander itself carried an excellent camera to image its surroundings. Extra sharp with a good color balance, the Terrain Camera was mounted at the top of the lander, with the ability to rotate 360 degrees. Before it died at the end of the first lunar day, this TCAM returned detailed images of the Moon. A helpful Twitter user in France, Techniques Spatiales, converted the camera's imagery into .png files, which can be found here.