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🔗 Computing 🔗 Computer Security 🔗 Computer Security/Computing

Capability-based security is a concept in the design of secure computing systems, one of the existing security models. A capability (known in some systems as a key) is a communicable, unforgeable token of authority. It refers to a value that references an object along with an associated set of access rights. A user program on a capability-based operating system must use a capability to access an object. Capability-based security refers to the principle of designing user programs such that they directly share capabilities with each other according to the principle of least privilege, and to the operating system infrastructure necessary to make such transactions efficient and secure. Capability-based security is to be contrasted with an approach that uses hierarchical protection domains.

Although most operating systems implement a facility which resembles capabilities, they typically do not provide enough support to allow for the exchange of capabilities among possibly mutually untrusting entities to be the primary means of granting and distributing access rights throughout the system. A capability-based system, in contrast, is designed with that goal in mind.

Capabilities as discussed in this article should not be confused with POSIX 1e/2c "Capabilities". The latter are coarse-grained privileges that cannot be transferred between processes.

🔗 Egypt

The Siwa Oasis (Arabic: واحة سيوة‎, Wāḥat Sīwah, IPA: [ˈwæːħet ˈsiːwæ]; Coptic: ⲥⲓⲟⲩⲁϩ Siwah; Berber languages: Isiwan, ⵉⵙⵉⵡⴰⵏ ) is an urban oasis in Egypt between the Qattara Depression and the Great Sand Sea in the Western Desert, 50 km (30 mi) east of the Libyan border, and 560 km (348 mi) from Cairo. About 80 km (50 mi) in length and 20 km (12 mi) wide, Siwa Oasis is one of Egypt's most isolated settlements with about 33,000 people, mostly Berbers, who developed a unique and isolated desert culture and a distinct dialect and language different than all other dialects called Siwi, they are also fluent in the Egyptian dialect of Arabic which is called "Masry" meaning Egyptian.

Its fame lies primarily in its ancient role as the home to an oracle of Ammon, the ruins of which are a popular tourist attraction which gave the oasis its ancient name Oasis of Amun Ra. Historically, it was part of Ancient Egypt.

🔗 Computing 🔗 Computing/Software 🔗 Linux

The magic SysRq key is a key combination understood by the Linux kernel, which allows the user to perform various low-level commands regardless of the system's state. It is often used to recover from freezes, or to reboot a computer without corrupting the filesystem. Its effect is similar to the computer's hardware reset button (or power switch) but with many more options and much more control.

This key combination provides access to powerful features for software development and disaster recovery. In this sense, it can be considered a form of escape sequence. Principal among the offered commands are means to forcibly unmount file systems, kill processes, recover keyboard state, and write unwritten data to disk. With respect to these tasks, this feature serves as a tool of last resort.

The magic SysRq key cannot work under certain conditions, such as a kernel panic or a hardware failure preventing the kernel from running properly.

🔗 Mathematics

A Penrose tiling is an example of an aperiodic tiling. Here, a tiling is a covering of the plane by non-overlapping polygons or other shapes, and aperiodic means that shifting any tiling with these shapes by any finite distance, without rotation, cannot produce the same tiling. However, despite their lack of translational symmetry, Penrose tilings may have both reflection symmetry and fivefold rotational symmetry. Penrose tilings are named after mathematician and physicist Roger Penrose, who investigated them in the 1970s.

There are several different variations of Penrose tilings with different tile shapes. The original form of Penrose tiling used tiles of four different shapes, but this was later reduced to only two shapes: either two different rhombi, or two different quadrilaterals called kites and darts. The Penrose tilings are obtained by constraining the ways in which these shapes are allowed to fit together. This may be done in several different ways, including matching rules, substitution tiling or finite subdivision rules, cut and project schemes, and coverings. Even constrained in this manner, each variation yields infinitely many different Penrose tilings.

Penrose tilings are self-similar: they may be converted to equivalent Penrose tilings with different sizes of tiles, using processes called inflation and deflation. The pattern represented by every finite patch of tiles in a Penrose tiling occurs infinitely many times throughout the tiling. They are quasicrystals: implemented as a physical structure a Penrose tiling will produce diffraction patterns with Bragg peaks and five-fold symmetry, revealing the repeated patterns and fixed orientations of its tiles. The study of these tilings has been important in the understanding of physical materials that also form quasicrystals. Penrose tilings have also been applied in architecture and decoration, as in the floor tiling shown.

🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography and steganography, plausibly deniable encryption describes encryption techniques where the existence of an encrypted file or message is deniable in the sense that an adversary cannot prove that the plaintext data exists.

The users may convincingly deny that a given piece of data is encrypted, or that they are able to decrypt a given piece of encrypted data, or that some specific encrypted data exists. Such denials may or may not be genuine. For example, it may be impossible to prove that the data is encrypted without the cooperation of the users. If the data is encrypted, the users genuinely may not be able to decrypt it. Deniable encryption serves to undermine an attacker's confidence either that data is encrypted, or that the person in possession of it can decrypt it and provide the associated plaintext.

In their pivotal 1996 paper, Ran Canetti, Cynthia Dwork, Moni Naor, and Rafail Ostrovsky introduced the concept of deniable encryption, a cryptographic breakthrough that ensures privacy even under coercion. This concept allows encrypted communication participants to plausibly deny the true content of their messages. Their work lays the foundational principles of deniable encryption, illustrating its critical role in protecting privacy against forced disclosures. This research has become a cornerstone for future advancements in cryptography, emphasizing the importance of deniable encryption in maintaining communication security. The notion of deniable encryption was used by Julian Assange and Ralf Weinmann in the Rubberhose filesystem.

🔗 Korea 🔗 China 🔗 East Asia 🔗 Languages 🔗 Korea/one or more inactive working groups

The Sinosphere, also known as the East Asian cultural sphere, or the Sinic world, encompasses multiple countries in East Asia and Southeast Asia that historically were heavily influenced by Chinese culture, norms and traditions. According to academic consensus, the Sinosphere comprises four entities: Greater China, Japan, Korea, and Vietnam. Other definitions may include Mongolia and Singapore, largely due to limited historical Chinese influences or increasing modern-day Chinese diaspora. The Sinosphere is not to be confused with Sinophone, which indicates countries where a Chinese-speaking population is dominant.

Imperial China was a major regional power in Eastern Asia and had exerted influence on tributary states and neighboring states, among which were Japan, Korea, and Vietnam. These interactions brought ideological and cultural influences rooted in Confucianism, Buddhism, and Taoism. During classical history, the four cultures shared a common imperial system under respective emperors. Chinese inventions influenced, and were in turn influenced by, innovations of the other cultures in governance, philosophy, science, and the arts. Written Classical Chinese became the regional lingua franca for literary and scientific exchange, and Chinese characters (Hanzi) became locally adapted in Japan as Kanji, Korea as Hanja, and Vietnam as chữ Hán.

In late classical history, the literary importance of classical Chinese diminished as Japan, Korea, and Vietnam each adopted their own literary device. Japan developed the Katakana and Hiragana scripts, Korea created Hangul, and Vietnam developed chữ Nôm (which is now rarely used; the modern Vietnamese alphabet is based on the Latin alphabet). Classical literature written in Chinese characters nonetheless remains an important legacy of Japanese, Korean, and Vietnamese cultures. In the 21st century, ideological and cultural influences of Confucianism and Buddhism remain visible in high culture and social doctrines.

🔗 Automobiles

A cyclecar was a type of small, lightweight and inexpensive car manufactured in Europe and the United States between 1910 and the early 1920s. The purpose of cyclecars was to fill a gap in the market between the motorcycle and the car.

The demise of cyclecars was due to larger cars – such as the Citroën Type C, Austin 7 and Morris Cowley – becoming more affordable. Small, inexpensive vehicles reappeared after World War II, and were known as microcars.

🔗 Technology 🔗 Transport

A paternoster (, , or ) or paternoster lift is a passenger elevator which consists of a chain of open compartments (each usually designed for two persons) that move slowly in a loop up and down inside a building without stopping. Passengers can step on or off at any floor they like. The same technique is also used for filing cabinets to store large amounts of (paper) documents or for small spare parts. The much smaller belt manlift which consists of an endless belt with steps and rungs but no compartments is also sometimes called a paternoster.

The name paternoster ("Our Father", the first two words of the Lord's Prayer in Latin) was originally applied to the device because the elevator is in the form of a loop and is thus similar to rosary beads used as an aid in reciting prayers.

The construction of new paternosters was stopped in the mid-1970s out of concern for safety, but public sentiment has kept many of the remaining examples open. By far most remaining paternosters are in Europe, with 230 examples in Germany, and 68 in the Czech Republic. Only three have been identified outside Europe: one in Malaysia, one in Sri Lanka, and another in Peru.

🔗 Brazil 🔗 Brands 🔗 Automobiles 🔗 Brazil/Transportation in Brazil

The Gurgel Itaipu E150 is an electric car, produced by the Brazilian automobile manufacturer Gurgel. The Itaipu was presented at the Salão do Automóvel in 1974, with an intended production start in December 1975. Only a few of these cars were produced and is today a collector's item. Top speed was of the first prototypes were of approximately 30 km/h (19 mph) and the latest models reached up to 60 km/h (37 mph). While about twenty pre-series cars were built, it was never commercialized. It was the first electric car built in Latin America, and, its specifications were comparable to similar models of the time (see CitiCar). The car was named after the hydro-electric dam and power plant on the border of Brazil and Paraguay.

The car's design was unique, a very compact trapezoidal two-seater. The car itself weighed a mere 460 kg (1,014 lb), with the remaining 320 kg (705 lb) consisting of batteries. The name "Itaipu" was brought back for a larger commercial vehicle in 1980, called the Itaipu E400. This was based on the Volkswagen-engined Gurgel G800.