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Hashcash
Hashcash is a proof-of-work system used to limit email spam and denial-of-service attacks. Hashcash was proposed in 1997 by Adam Back and described more formally in Back's 2002 paper "Hashcash – A Denial of Service Counter-Measure". In Hashcash the client has to concatenate a random number with a string several times and hash this new string. It then has to do so over and over until a hash beginning with a certain number of zeros is found. Background The idea "...to require a user to compute a moderately hard, but not intractable function..." was proposed by ynthia Dworkand oni Naorin their 1992 paper "Pricing via Processing or Combatting Junk Mail".{Cite book, last1=Dwork, first1=Cynthia, pages=139–147, last2=Naor, first2=Moni, title=Advances in Cryptology — CRYPTO' 92 , chapter=Pricing via Processing or Combatting Junk Mail , series=Lecture Notes in Computer Science, publisher=Springer, doi=10.1007/3-540-48071-4_10, date=2001-05-18, volume=740, isbn=978-3-540-57340-1, doi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proof-of-work
Proof of work (also written as proof-of-work, an abbreviated PoW) is a form of Cryptography, cryptographic proof (truth), proof in which one party (the ''prover'') proves to others (the ''verifiers'') that a certain amount of a specific computational effort has been expended. Verifiers can subsequently confirm this expenditure with minimal effort on their part. The concept was first implemented in Hashcash by Moni Naor and Cynthia Dwork in 1993 as a way to deter denial-of-service attacks and other service abuses such as spam (electronic), spam on a network by requiring some work from a service requester, usually meaning processing time by a computer. The term "proof of work" was first coined and formalized in a 1999 paper by Markus Jakobsson and Ari Juels. The concept was adapted to digital tokens by Hal Finney (computer scientist), Hal Finney in 2004 through the idea of "reusable proof of work" using the 160-bit secure hash algorithm 1 (SHA-1). Proof of work was later popularized ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adam Back
Adam Back (born July 1970) is a British cryptographer and cypherpunk. He is the CEO of Blockstream, which he co-founded in 2014. He invented Hashcash, which is used in the bitcoin mining process. Life Back was born in London, England, in July 1970. His first computer was a ZX81, Sinclair ZX81. He taught himself BASIC, Basic, and spent his time reverse engineering video games, finding decryption keys in Software suite, software packages. He completed his A-Levels, A levels in advanced mathematics, physics, and economics. He has a computer science Doctor of Philosophy, PhD in distributed systems from the University of Exeter. During his PhD, Back worked with compilers to make use of parallel computers in a semi automated way. He became interested in Pretty Good Privacy, PGP encryption, Electronic cash system, electronic cash and Anonymous remailer, remailers. He spent two thirds of his time working with encryption. After graduation, Back spent his career as a consultant in Start ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Function (cryptography)
A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with a fixed size of n bits) that has special properties desirable for a cryptographic application: * the probability of a particular n-bit output result (hash value) for a random input string ("message") is 2^ (as for any good hash), so the hash value can be used as a representative of the message; * finding an input string that matches a given hash value (a ''pre-image'') is infeasible, ''assuming all input strings are equally likely.'' The ''resistance'' to such search is quantified as security strength: a cryptographic hash with n bits of hash value is expected to have a ''preimage resistance'' strength of n bits, unless the space of possible input values is significantly smaller than 2^ (a practical example can be found in ); * a ''second preimage'' resistance strength, with the same expectations, refers to a similar problem of finding a second message that mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bitcoin
Bitcoin (abbreviation: BTC; Currency symbol, sign: ₿) is the first Decentralized application, decentralized cryptocurrency. Based on a free-market ideology, bitcoin was invented in 2008 when an unknown entity published a white paper under the pseudonym of Satoshi Nakamoto. Use of bitcoin as a currency began in 2009, with the release of its open-source software, open-source implementation. In 2021, Bitcoin in El Salvador, El Salvador adopted it as legal tender. It is mostly seen as an investment and has been described by some scholars as an economic bubble. As bitcoin is pseudonymous, Cryptocurrency and crime, its use by criminals has attracted the attention of regulators, leading to Legality of cryptocurrency by country or territory, its ban by several countries . Bitcoin works through the collaboration of computers, each of which acts as a Node (networking), node in the peer-to-peer bitcoin network. Each node maintains an independent copy of a public distributed ledger of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SHA-256
SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. They are built using the Merkle–Damgård construction, from a one-way compression function itself built using the Davies–Meyer structure from a specialized block cipher. SHA-2 includes significant changes from its predecessor, SHA-1. The SHA-2 family consists of six hash functions with digests (hash values) that are 224, 256, 384 or 512 bits: SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, SHA-512/256. SHA-256 and SHA-512 are hash functions whose digests are eight 32-bit and 64-bit words, respectively. They use different shift amounts and additive constants, but their structures are otherwise virtually identical, differing only in the number of rounds. SHA-224 and SHA-384 are truncated versions of SHA-256 and SHA-512 respectively, computed with different initial values. SHA-512/224 and SHA-512/256 are also trunc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SpamAssassin
Apache SpamAssassin is a computer program used for e-mail spam filtering. It uses a variety of spam-detection techniques, including DNS and fuzzy checksum techniques, Bayesian filtering, external programs, blacklists and online databases. It is released under the Apache License 2.0 and is a part of the Apache Foundation since 2004. The program can be integrated with the mail server to automatically filter all mail for a site. It can also be run by individual users on their own mailbox and integrates with several mail programs. Apache SpamAssassin is highly configurable; if used as a system-wide filter it can still be configured to support per-user preferences. History Apache SpamAssassin was created by Justin Mason, who had maintained a number of patches against an earlier program named ''filter.plx'' by Mark Jeftovic, which in turn was begun in August 1997. Mason rewrote all of Jeftovic's code from scratch and uploaded the resulting codebase to SourceForge on April 20, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spam In Blogs
Spam in blogs (also known as blog spam, comment spam, or social spam) is a form of spamdexing which utilizes internet sites that allow content to be publicly posted, in order to artificially inflate their website ranking by linking back (also referred to as backlinking) to their web pages. Backlinking helps search algorithms determine the popularity of a web page, which plays a major role for search engines like Google and Microsoft Bing to decide a web page ranking on a certain search query. This helps the spammer's website to list ahead of other sites for certain searches, which helps them to increase the number of visitors to their website. It may be done by posting random comments on other blog websites (usually by an automated process), or by copying other websites' content and using it on free-to-use publishing services like Blogger and WordPress or publicly accessible wikis, digital guest books, and internet forums. Note that ''blog spam'' also has another meaning, spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blog
A blog (a Clipping (morphology), truncation of "weblog") is an informational website consisting of discrete, often informal diary-style text entries also known as posts. Posts are typically displayed in Reverse chronology, reverse chronological order so that the most recent post appears first, at the top of the web page. In the 2000s, blogs were often the work of a single individual, occasionally of a small group, and often covered a single subject or topic. In the 2010s, multi-author blogs (MABs) emerged, featuring the writing of multiple authors and sometimes professionally Editing, edited. MABs from newspapers, other News media, media outlets, universities, think tanks, advocacy groups, and similar institutions account for an increasing quantity of blog Web traffic, traffic. The rise of Twitter and other "microblogging" systems helps integrate MABs and single-author blogs into the news media. ''Blog'' can also be used as a verb, meaning ''to maintain or add content to a blog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mozilla Thunderbird
Mozilla Thunderbird is a free and open-source email client that also functions as a personal information manager with a Digital calendar, calendar and contactbook, as well as an RSS feed reader, chat client (IRC/XMPP/Matrix (protocol), Matrix), and news client. Operated by MZLA Technologies Corporation, a subsidiary of the Mozilla Foundation, Thunderbird is an independent, community-driven project that is managed and overseen by the Thunderbird Council, which is elected by the Thunderbird community. As a cross-platform application, Thunderbird is available for Windows, macOS, FreeBSD, Android (operating system), Android, and Linux. The project strategy was originally modeled after that of Mozilla's Firefox, and Thunderbird is an interface built on top of that Web browser. Overview General Thunderbird is an e-mail, newsgroup, news feed, and instant messaging client with personal information manager (PIM) functionality, inbuilt since version 78.0 and previously available from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SourceForge
SourceForge is a web service founded by Geoffrey B. Jeffery, Tim Perdue, and Drew Streib in November 1999. SourceForge provides a centralized software discovery platform, including an online platform for managing and hosting open-source software projects, and a directory for comparing and reviewing B2B software that lists over 104,500 business software titles. It provides source code repository hosting, bug tracking, mirroring of downloads for load balancing, a wiki for documentation, developer and user mailing lists, user-support forums, user-written reviews and ratings, a news bulletin, micro-blog for publishing project updates, and other features. SourceForge was one of the first to offer this service free of charge to open-source projects. Since 2012, the website has run on Apache Allura software. SourceForge offers free hosting and free access to tools for developers of free and open-source software. , the SourceForge repository claimed to host more than 502,00 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
