In
military
A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...
terminology, a countersign is a sign, word, or any other signal previously agreed upon and required to be exchanged between a
sentry
Sentry or The Sentry may refer to:
Comics
*Sentry (Kree)
*Sentry (Curtis Elkins)
*Sentry (Robert Reynolds)
*Senator Ward (comics) or Sentry
Vehicles
*Sentry (AUV), an autonomous underwater vehicle used to measure deep-ocean data
* E-3 Sentry AWAC ...
or guard and anybody approaching his or her post. The term usually encompasses both the sign given by the approaching party as well as the sentry's reply. However, in some armies, the countersign is strictly the reply of the sentry to the password given by the person approaching. A well-known sign/countersign used by the Allied forces on
D-Day
The Normandy landings were the landing operations and associated airborne operations on Tuesday, 6 June 1944 of the Allied invasion of Normandy in Operation Overlord during World War II. Codenamed Operation Neptune and often referred to as D ...
during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
: the challenge/sign was "flash", the
password
A password, sometimes called a passcode (for example in Apple devices), is secret data, typically a string of characters, usually used to confirm a user's identity. Traditionally, passwords were expected to be memorized, but the large number of ...
"thunder", and the countersign (to challenge the person giving the first code word) "Welcome".
D-Day By Jon E. Lewis, Lord Carver
p. 40 Some armies will select passwords or challenges that are difficult to pronounce by the enemy force speaking a different language.
In computer networks
A similar technique is becoming common in computer networking
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ma ...
, particularly for banking web sites. For example, (as in Bank of America
The Bank of America Corporation (often abbreviated BofA or BoA) is an American multinational investment bank and financial services holding company headquartered at the Bank of America Corporate Center in Charlotte, North Carolina. The bank w ...
's "SiteKey" system), a user might enter his or her user-ID, but withhold the corresponding password until the server replied to the user-ID with a previously agreed-upon phrase and/or image. So long as the connection is secure, and the user can choose from a wide range of phrases and/or images in the set-up process, they can be confident that they are signing on to the legitimate site, rather than to a spoofed one.
In literature
The opening lines of William Shakespeare
William Shakespeare ( 26 April 1564 – 23 April 1616) was an English playwright, poet and actor. He is widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's nation ...
's play ''Hamlet
''The Tragedy of Hamlet, Prince of Denmark'', often shortened to ''Hamlet'' (), is a tragedy written by William Shakespeare sometime between 1599 and 1601. It is Shakespeare's longest play, with 29,551 words. Set in Denmark, the play depicts ...
'' are between soldiers on duty are viewed as representing a crude sign, where the line "Long live the King!" was a sign between soldiers:
:''Bernardo. Who's there?''
:''Francisco. Nay, answer me. Stand and unfold yourself.''
:''Bernardo. Long live the King!''
:''Francisco. Bernardo?''
:''Bernardo. He.''
See also
* Challenge–response authentication
In computer security, challenge–response authentication is a family of protocols in which one party presents a question ("challenge") and another party must provide a valid answer ("response") to be authenticated.
The simplest example of a ch ...
* Shibboleth
A shibboleth (; hbo, , šībbōleṯ) is any custom or tradition, usually a choice of phrasing or even a single word, that distinguishes one group of people from another. Shibboleths have been used throughout history in many societies as passwor ...
References
{{reflist
Military terminology