This article is about identification. For anonymity in Wikipedia see Wikipedia:Anonymity. For other uses see Anonymous (disambiguation) and Anonymus (disambiguation). This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (March 2009)

Anonymity is derived from the Greek word anonymia meaning "without a name" or "namelessness". In colloquial use anonymity typically refers to the state of an individual's personal identity or personally identifiable information being publicly unknown.

There are many reasons why a person might choose to obscure their identity and become anonymous. Several of these reasons are legal legitimate and socially approved ofmany acts of charity are performed anonymously as benefactors do not wish for whatever reason to be acknowledged for their action. Someone who feels threatened by someone else might attempt to hide from the threat behind various means of anonymity a witness to a crime can seek to avoid retribution for example by anonymously calling a crime tipline. There are also many illegal reasons to hide behind anonymity. Criminals typically try to keep themselves anonymous either to conceal the fact that a crime has been committed or to avoid capture. Anonymity may also be created unintentionally through the loss of identifying information due to the passage of time or a destructive event.

The term "anonymous message" typically refers to a message (which is for example transmitted over some form of a network) that does not carry any information about its sender and its intended recipient. It is therefore unclear if multiple such messages have been sent by the same sender or if they have the same intended recipient.

The problem of determining whether or not the identity of a communication partner is the same as one previously encountered is the problem of authentication.

In mathematics in reference to an arbitrary element (e.g. a human an object a computer) within a well-defined set (called the "anonymity set") "anonymity" of that element refers to the property of that element of not being identifiable within this set. If it is not identifiable then the element is said to be "anonymous". Contents 1 Compared with pseudonymity 2 Means of obtaining anonymity 3 Anonymity and social situations 4 Anonymity commerce and crime 5 Anonymity in charity 6 Issues facing the anonymous 7 Referring to the anonymous 8 Anonymity and the press 9 Anonymity on the Internet 10 Anonymity and politics 11 Anonymity and pseudonymity in art 12 Mathematics of anonymity 13 See also 14 References Compared with pseudonymity

Sometimes it is desired that a person can establish a long-term relationship (such as a reputation) with some other entity without necessarily disclosing personally identifying information to that entity. In this case it may be useful for the person to establish a unique identifier called a pseudonym with the other entity. Examples of pseudonyms are pen names nicknames credit card numbers student numbers bank account numbers and IP addresses. A pseudonym enables the other entity to link different messages from the same person and thereby the maintenance of a long-term relationship.

Someone using a pseudonym would be strictly considered to be using "pseudonymity" not "anonymity" but sometimes the term "anonymity" is used to refer to both (in general a situation where the legal identity of the person is disguised). Means of obtaining anonymity

Anonymity is a result of not having identifying characteristics (such as a name or description of physical appearance) disclosed. This can occur from a lack of interest in learning the nature of such characteristics or through intentional efforts to hide these characteristics. An example of the former would include a brief encounter with a stranger when learning the other person's name is not deemed necessary. An example of the latter would include someone hiding behind clothing that covers identifying features like hair color scars or tattoos in order to avoid identification.

In some cases anonymity is reached unintentionally as is often the case with victims of crimes or war battles when a body is discovered in such a state that the physical features used to identify someone are no longer present. Anonymity is not always found in such morbid situations however. As an example a winner of a lottery jackpot is anonymous (one of however many play the lottery) until that person turns in the winning lottery ticket. Anonymity may also be created through a gradual eroding of ownership information such as the passage of time and loss of attribution to a saying. For example the quote "Ignorance is Bliss" originally had a known author but over time information on author's identity was obscured and has disappeared. Anonymity and social situations Anonymity may reduce the accountability one perceives to have for their actions and removes the impact these actions might otherwise have on their reputation. This can have dramatic effects both useful and harmful. In conversational settings anonymity may allow people to reveal personal history and feelings without fear of later embarrassment. Electronic conversational media can provide physical isolation in addition to anonymity. This prevents physical retaliation for remarks and prevents negative or taboo behavior or discussion from tarnishing the reputation of the speaker. This can be beneficial when discussing very private matters or taboo subjects or expressing views or revealing facts which may put someone in physical financial or legal danger (such as illegal activity or unpopular or outlawed political views). With few perceived negative consequences anonymous or semi-anonymous forums often provide a soapbox for disruptive conversational behavior. The term Internet troll is sometimes used to refer to those who do this online. Relative anonymity is often enjoyed in large crowds. Different people have different psychological and philosophical reactions to this development especially as a modern phenomenon. This anonymity is an important factor in crowd psychology and behavior in situations such as a riot. This perceived anonymity can be compromised by technologies such as photography. Anonymity commerce and crime Anonymous commercial transactions can protect the privacy of consumers. Some consumers prefer to use cash when buying everyday goods (like groceries or tools) to prevent sellers from aggregating information or soliciting them in the future. Credit cards are linked to a person's name and can be used to discover other information such as postal address phone number etc. The ecash system was developed to allow secure anonymous transactions. When purchasing taboo goods and services anonymity makes many potential consumers more comfortable with or more willing to engage in the transaction. Many loyalty programs use cards which personally identify the consumer engaging in each transaction (possibly for later solicitation or for redemption or security purposes) or which act as a numerical pseudonym for use in data mining. Anonymity can also be used as a protection against legal prosecution. For example when committing a robbery many criminals will obscure their faces to avoid identification. In organized crime groups of criminals may collaborate on a certain project without revealing to each other their names or other personally identifiable information. The movie The Thomas Crown Affair depicted a fictional collaboration by people who had never previously met and did not know who had recruited them. The anonymous purchase of a gun or knife to be used in a crime helps prevent linking an abandoned weapon to the identity of the perpetrator. Anonymity in charity There are two aspects one giving to a large charitable organization obscures the beneficiary of a donation from the benefactor the other is giving anonymously to obscure the benefactor both from the beneficiary and from everyone else. There are many reasons this is done. Anonymous charity has long been a widespread and durable moral precept of many ethical and religious systems as well as being in practice a widespread human activity. A benefactor may not wish to establish any relationship with the beneficiary particularly if the beneficiary is perceived as being unsavory. Benefactors may not wish to identify themselves as capable of giving. A benefactor may wish to improve the world as long as no one knows who did it out of modesty wishing to avoid publicity.1 Issues facing the anonymous Attempts at anonymity are not always met with support from society. There is a trend in society to mistrust someone who makes an effort to maintain their anonymity. This is often summed up in the statement "You wouldn't want to stay anonymous unless you had something to hide."citation needed The implication is that there is no legitimate reason to obscure one's identity from the world as a whole. Anonymity sometimes clashes with the policies and procedures of governments or private organizations. In the United States disclosure of identity is required to be able to vote though the secret ballot prevents disclosure of how individuals voted. In airports in most countries passengers are not allowed to board flights unless they have identified themselves to some sort of airline or transportation security personnel typically in the form of the presentation of an identification card. On the other hand some policies and procedures require anonymity. Referring to the anonymous When it is necessary to refer to someone who is anonymous it is typically necessary to create a type of pseudo-identification for that person. In literature the most common way to state that the identity of an author is unknown is to refer to them as simply "Anonymous." This is usually the case with older texts in which the author is long dead and unable to claim authorship of a work. When the work claims to be that of some famous author the pseudonymous author is identified as "Pseudo-" as in Pseudo-Dionysius the Areopagite an author claimingand long believedto be Dionysius the Areopagite an early Christian convert. Anonymus in its Latin spelling generally with a specific city designation is traditionally used by scholars in the humanities to refer to an ancient writer whose name is not known or to a manuscript of their work. Very many such writers have left valuable historical or literary records: an incomplete list of such Anonymi is at Anonymus. In the history of art many painting workshops can be identified by their characteristic style and discussed and the workshop's output set in chronological order. Sometimes archival research later identifies the name as when the "Master of Flmalle"defined by three paintings in the Stdelsches Kunstinstitut in Frankfurt was identified as Robert Campin. The 20th-century art historian Bernard Berenson methodically identified numerous early Renaissance Florentine and Sienese workshops under such sobriquets as "Amico di Sandro" for an anonymous painter in the immediate circle of Sandro Botticelli. In legal cases a popularly accepted name to use when it is determined that an individual needs to maintain anonymity is "John Doe". This name is often modified to "Jane Doe" when the anonymity-seeker is female. The same names are also commonly used when the identification of a dead person is not known. The semi-acronym Unsub is used as law enforcement slang for "Unknown Subject of an Investigation". The military often feels a need to honor the remains of soldiers for whom identification is impossible. In many countries such a memorial is named the Tomb of the Unknown Soldier. Anonymity and the press Most modern newspapers and magazines attribute their articles to individual editors or to news agencies. An exception is the British weekly The Economist which may be the world's only un-bylined paper. All British newspapers run their leaders (i.e. editorials) anonymously. Anonymity on the Internet Main article: Anonymous post Most commentary on the Internet is essentially done anonymously using unidentifiable pseudonyms. While these names can take on an identity of their own they are frequently separated from and anonymous from the actual author and according to the University of Stockholm creating more freedom of expression and less accountability.2 The online encyclopedia Wikipedia is collaboratively written mostly by authors using either unidentifiable pseudonyms or IP address identifiers although a few have used identified pseudonyms or their real names. Full anonymity on the Internet however is not guaranteed since IP addresses in principle can be tracked allowing to identify the computer from which a certain post was made albeit not the actual user. Anonymizing services such as I2P - The Anonymous Network or Tor address the issue of IP tracking. Their distributed technology approach may grant a higher degree of security than centralized anonymizing services where a central point exists that could disclose one's identity. Sites such as Chatroulette and Omegle capitalize on the current fascination with anonymity. They are examples of anonymous chat or stranger chat. Anonymity and politics Modern pasquinades glued to the base of Pasquino one of the Talking Statues of Rome. The history of anonymous expression in political dissent is both long and with important effect as in the Letters of Junius or Voltaire's Candide or scurrilous as in pasquinades. In the tradition of anonymous British political criticism the Federalist Papers were anonymously authored. Without the public discourse on the controversial contents of the U.S. Constitution ratification would likely have taken much longer as individuals worked through the issues. The United States Declaration of Independence however was not anonymous. If it had been unsigned it might well have been less effective. John Perry Barlow Joichi Ito and other US bloggers express a very strong support for anonymous editing as one of the basic requirements of open politics as conducted on the Internet.3 Saipansucks.com is an example of an anonymously written website that socially and politically criticizes the United States' Commonwealth of the Northern Mariana Islands and UticaSux.com politically criticizes the local government of Utica New York in the United States. Anonymity and pseudonymity in art Anonymity is directly related to the concept of obscurantism or pseudonymity where an artist or group attempts to remain anonymous for various reasons not limited to: adding an element of mystique to themselves and/or their work attempting to avoid what is known as the "cult of personality" or hero worship where the charisma good looks wealth and/or other unrelated or mildly related aspects of the person(s) is the main reason for interest in their work rather than the work itself; also the ability to break into a field or area of interest normally dominated by males such as James Tiptree Jr the famous science fiction author who was actually a woman named Alice Bradley Sheldon as seems to also be the case with JT LeRoy. The reasons for choosing this approach vary. Some such as Thomas Pynchon and J. D. Salinger who seem to want to avoid the "limelight" of popularity or simply want to live private lives. Some others include The Residents and until 2004 musician Jandek. This is frequently applied in fiction from The Lone Ranger Superman and Batman where a hidden identity is assumed. Mathematics of anonymity An example: Suppose that only Alice Bob and Carol have the keys to a bank safe and that one day the contents of the safe are missing (without the lock being violated). Without any additional information we do not know for sure whether it was Alice Bob or Carol who opened the safe; the perpetrator remains anonymous. In particular each of the elements in Alice Bob Carol has a 1/3 chance of being the perpetrator. However as long as none of them has been identified as being the perpetrator with 100% certainty we can say that the perpetrator remains anonymous. Anonymity is not an absolute. That is the degree of anonymity one enjoys may vary. In the above example if Carol has an ironclad alibi at the time of the perpetration then we may deduce that it must have been either Alice or Bob who opened the safe. That is the probability of the elements Alice Bob Carol of being the perpetrator is now 1/2 1/2 and 0 respectively. This clearly amounts to a reduction of the perpetrator's anonymity (i.e. although the perpetrator still remains anonymous it is now more likely than before that (s)he is either Alice or Bob). See also Look up anon anonymity or anonymous in Wiktionary the free dictionary. I2P Anonymity application Anonymous web browsing List of anonymously published works Anonymous P2P Friend-to-friend Private P2P Personally identifiable information Pseudonymity Pseudonymization John Doe Crypto-anarchism Internet privacy Privacy software FLAIM Anonymous (group) Java Anon Proxy References Donors Increasingly Make Their Big Gifts Anonymously Chronicle Analysis Finds By Sam Kean (January 09 2008) The Chronicle of Philanthropy Anonymity on the Internet By Jacob Palme and Mikael Berglund - Jacob Palme's Home Page The Infrastructure of Democracy