Topic: Computing/Computer Security (Page 3)
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🔗 Bitcoin Cryptocurrency
Bitcoin (â‚¿) is a cryptocurrency. It is a decentralized digital currency without a central bank or single administrator that can be sent from user to user on the peer-to-peer bitcoin network without the need for intermediaries.
Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto and started in 2009 when its source code was released as open-source software. Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. Research produced by University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.
Bitcoin has been criticized for its use in illegal transactions, its high electricity consumption, price volatility, and thefts from exchanges. Some economists, including several Nobel laureates, have characterized it as a speculative bubble. Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.
🔗 XKeyscore
XKeyscore (XKEYSCORE or XKS) is a secret computer system used by the United States National Security Agency (NSA) for searching and analyzing global Internet data, which it collects in real time. The NSA has shared XKeyscore with other intelligence agencies, including the Australian Signals Directorate, Canada's Communications Security Establishment, New Zealand's Government Communications Security Bureau, Britain's Government Communications Headquarters, Japan's Defense Intelligence Headquarters, and Germany's Bundesnachrichtendienst.
In July 2013, Edward Snowden publicly revealed the program's purpose and use by the NSA in The Sydney Morning Herald and O Globo newspapers. The code name was already public knowledge because it was mentioned in earlier articles, and, like many other code names, it appears in job postings and online résumés of employees.
On July 3, 2014, German public broadcaster Norddeutscher Rundfunk, a member of ARD, published excerpts of XKeyscore's source code. A team of experts analyzed the source code.
🔗 .XIP
An .XIP file is a XAR archive which can be digitally signed for integrity. The .XIP file format was introduced in OS X 10.9, along with Apple's release of Swift. .XIP allows for a digital signature to be applied and verified on the receiving system before the archive is expanded. When a XIP file is opened (by double-clicking), Archive Utility will automatically expand it (but only if the digital signature is intact).
Apple has reserved the right to use the .XIP file format exclusively, removing it from public use since release. Starting with macOS Sierra, only .XIP archives signed by Apple will be expanded. Developers who had been using .XIP archives were required to move to using signed installer packages or disk images.