Topic: computing (Page 37)
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π Domain Fronting
Domain fronting is a technique for Internet censorship circumvention that uses different domain names in different communication layers of an HTTPS connection to discreetly connect to a different target domain than is discernable to third parties monitoring the requests and connections.
Due to quirks in security certificates, the redirect systems of the content delivery networks (CDNs) used as 'domain fronts', and the protection provided by HTTPS, censors are typically unable to differentiate circumvention ("domain-fronted") traffic from overt non-fronted traffic for any given domain name. As such they are forced to either allow all traffic to the domain frontβincluding circumvention trafficβor block the domain front entirely, which may result in expensive collateral damage and has been likened to "blocking the rest of the Internet".
Domain fronting does not conform to HTTP standards that require the SNI extension and HTTP Host header to contain the same domain. Many large cloud service providers, including Amazon, Microsoft, and Google, actively prohibit domain fronting, which has limited it as a censorship bypass technique. Pressure from censors in Russia and China is thought to have contributed to these prohibitions, but domain fronting can also be used maliciously.
A newer variant of domain fronting, domain hiding, passes an encrypted request for one resource (say, a website), concealed behind an unencrypted (plaintext) request for another resource whose DNS records are stored in the same cloud. It has much the same effect. Refraction networking is an application of the broader principle.
π Lace Card
A lace card is a punched card with all holes punched (also called a whoopee card, ventilator card, flyswatter card, or IBM doily). They were mainly used as practical jokes to cause disruption in card readers. Card readers tended to jam when a lace card was inserted, as the resulting card had too little structural strength to avoid buckling inside the mechanism. Card punches could also jam trying to produce cards with all holes punched, owing to power-supply problems. When a lace card was fed through the reader, a card knife or card saw (a flat tool used with punched card readers and card punches) was needed to clear the jam.
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- "Lace Card" | 2023-06-23 | 23 Upvotes 5 Comments
π 2024 CrowdStrike incident: The largest IT outage in history
On 19 July 2024, a faulty update to security software produced by CrowdStrike, an American cybersecurity company, caused innumerable computers and virtual machines running Microsoft Windows to crash. Businesses and governments around the globe were affected by what one expert called the "largest IT outage in history".
Among the industries that were disrupted were airlines, airports, banks, hotels, hospitals, stock markets, and broadcasting; governmental services such as emergency numbers and websites were also affected. The error was discovered and a fix was made on the same day, but the outage continued to delay airline flights, cause problems in processing electronic payments, and disrupt emergency services.
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- "2024 CrowdStrike incident: The largest IT outage in history" | 2024-07-19 | 24 Upvotes 4 Comments
π Nagle's Algorithm
Nagle's algorithm is a means of improving the efficiency of TCP/IP networks by reducing the number of packets that need to be sent over the network. It was defined by John Nagle while working for Ford Aerospace. It was published in 1984 as a Request for Comments (RFC) with title Congestion Control in IP/TCP Internetworks in RFCΒ 896.
The RFC describes what he called the "small-packet problem", where an application repeatedly emits data in small chunks, frequently only 1 byte in size. Since TCP packets have a 40-byte header (20 bytes for TCP, 20 bytes for IPv4), this results in a 41-byte packet for 1 byte of useful information, a huge overhead. This situation often occurs in Telnet sessions, where most keypresses generate a single byte of data that is transmitted immediately. Worse, over slow links, many such packets can be in transit at the same time, potentially leading to congestion collapse.
Nagle's algorithm works by combining a number of small outgoing messages and sending them all at once. Specifically, as long as there is a sent packet for which the sender has received no acknowledgment, the sender should keep buffering its output until it has a full packet's worth of output, thus allowing output to be sent all at once.
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- "Nagle's Algorithm" | 2022-12-30 | 25 Upvotes 2 Comments
π DNA Computing
DNA computing is a branch of computing which uses DNA, biochemistry, and molecular biology hardware, instead of the traditional silicon-based computer technologies. Research and development in this area concerns theory, experiments, and applications of DNA computing. The term "molectronics" has sometimes been used, but this term has already been used for an earlier technology, a then-unsuccessful rival of the first integrated circuits; this term has also been used more generally, for molecular-scale electronic technology.
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- "DNA Computing" | 2018-12-16 | 11 Upvotes 15 Comments
π Background of .plan files: the 1977 Finger Protocol
In computer networking, the Name/Finger protocol and the Finger user information protocol are simple network protocols for the exchange of human-oriented status and user information.
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- "Background of .plan files: the 1977 Finger Protocol" | 2011-12-18 | 19 Upvotes 7 Comments
π Jensen's Device
Jensen's Device is a computer programming technique that exploits call by name. It was devised by Danish computer scientist JΓΈrn Jensen, who worked with Peter Naur at Regnecentralen. They worked on the GIER Algol compiler, one of the earliest correct implementations of ALGOL 60. ALGOL 60 used call by name.
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- "Jensen's Device" | 2015-08-03 | 14 Upvotes 11 Comments
π Music Macro Language
Music Macro Language (MML) is a music description language used in sequencing music on computer and video game systems.
π Homoiconicity
In computer programming, homoiconicity (from the Greek words homo- meaning "the same" and icon meaning "representation") is a property of some programming languages. A language is homoiconic if a program written in it can be manipulated as data using the language, and thus the program's internal representation can be inferred just by reading the program itself. For example, a Lisp program is written as a regular Lisp list, and can be manipulated by other Lisp code. In homoiconic languages, all code can be accessed and transformed as data, using the same representation. This property is often summarized by saying that the language treats "code as data".
In a homoiconic language, the primary representation of programs is also a data structure in a primitive type of the language itself. This makes metaprogramming easier than in a language without this property: reflection in the language (examining the program's entities at runtime) depends on a single, homogeneous structure, and it does not have to handle several different structures that would appear in a complex syntax.
As noted above, a commonly cited example is Lisp, which was created to allow for easy list manipulations and where the structure is given by S-expressions that take the form of nested lists. Lisp programs are written in the form of lists; the result is that the program can access its own functions and procedures while running, and programmatically alter itself on the fly. Homoiconic languages typically include full support of syntactic macros, allowing the programmer to express transformations of programs in a concise way. Examples are the programming languages Clojure (a contemporary dialect of Lisp), Rebol (also its successor Red), Refal, Prolog, and more recently Julia.
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- "Homoiconicity" | 2016-01-19 | 20 Upvotes 5 Comments
π The Complexity of Songs
"The Complexity of Songs" is a journal article published by computer scientist Donald Knuth in 1977, as an in-joke about computational complexity theory. The article capitalizes on the tendency of popular songs to devolve from long and content-rich ballads to highly repetitive texts with little or no meaningful content. The article notes that a song of length N words may be produced remembering, e.g., only O(log N) words ("space complexity" of the song).
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- "The Complexity of Songs" | 2018-04-08 | 20 Upvotes 5 Comments