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== '''[[Active attack]]''' ==
== '''[[William Morris]]''' ==
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In [[cryptography]] an '''active attack''' on a communications system is one in which the attacker changes the communication. He may create, forge, alter, replace, block or reroute messages. This contrasts with a [[passive attack]] in which the attacker only eavesdrops; he may read messages he is not supposed to see, but he does not alter messages.
'''William Morris''' (1834-1896), an Englishman of distant Welsh origins, was a writer, a businessman, a pioneer of the [[Arts and Crafts movement]], and an early [[socialism|socialist]]. As a writer, he produced [[poetry]], translations of Nordic literature, historical and [[fantasy]] [[novel]]s, and socialist propaganda, which included journalism, pamphleteering, verse, and two novels.


== Active attacks on communication ==
His business, Morris & Co, produced individually crafted [[furniture]], [[stained glass]], [[carpet]]s, [[tapestry|tapestries]], and [[wallpaper]], using techniques he had mastered himself, design being shared with a small group of others.  It won contracts for the complete fitting out of rooms and even buildings, as well as making retail sales through a shop in Oxford Street, [[London]].  He also founded the Kelmscott Press.  Both these enterprises were perfectionist and elitist in nature.  He recognised that the [[elitism]] was contrary to his principles, but defended himself on the grounds that the revolution could not come immediately.  The perfectionism was one of the guiding inspirations of the Arts and Crafts movement.


Active attacks that target the communication system itself include:
''[[William Morris|.... (read more)]]''
* [[man-in-the-middle attack]]; the attacker tricks both communicating parties into communicating with him; they think they are talking to each other
* [[Stream_cipher#Rewrite_attacks | rewrite attacks]]; the attacker can replace a message with anything he chooses
 
'''Successful active attacks are devastating!''' If the attacker can replace messages and have them taken as genuine, it is all over. The security system is then at best worthless; at worst it is of great value to the enemy.
 
Fortunately, these attacks are '''generally hard to execute'''. The attacker must not only intercept messages, break whatever [[cryptography]] is in use (often ''both'' an authentication mechanism and a cipher), and send off his bogus message; he also has to block delivery of the genuine message. Moreover, he has to do it all '''in real time''', fast enough to avoid alerting his victims and to beat whatever synchronisation mechanisms the network may be using. A cryptosystem that an enemy can break in hours or days would generally be considered insecure, even worthless, but it will prevent active attacks as long as the enemy cannot break it quickly enough to replace messages.
 
''[[Active attack|.... (read more)]]''


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Revision as of 20:43, 4 August 2013

William Morris

William Morris (1834-1896), an Englishman of distant Welsh origins, was a writer, a businessman, a pioneer of the Arts and Crafts movement, and an early socialist. As a writer, he produced poetry, translations of Nordic literature, historical and fantasy novels, and socialist propaganda, which included journalism, pamphleteering, verse, and two novels.

His business, Morris & Co, produced individually crafted furniture, stained glass, carpets, tapestries, and wallpaper, using techniques he had mastered himself, design being shared with a small group of others. It won contracts for the complete fitting out of rooms and even buildings, as well as making retail sales through a shop in Oxford Street, London. He also founded the Kelmscott Press. Both these enterprises were perfectionist and elitist in nature. He recognised that the elitism was contrary to his principles, but defended himself on the grounds that the revolution could not come immediately. The perfectionism was one of the guiding inspirations of the Arts and Crafts movement.

.... (read more)

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