Totally positive matrix - Revision history

128.101.152.183: /* Definition */

2014-10-10T19:21:57Z

Definition

← Older revision		Revision as of 21:21, 10 October 2014
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	~~{{inline\|date=June 2010}}~~

	A '''mimic function''' changes a file <math>A</math> so it assumes the statistical properties of another file <math>B</math>. That is, if <math>p(t,A)</math> is the probability of some substring <math>t</math> occurring in <math>A</math>, then a mimic function <math>f</math>, recodes <math>A</math> so that <math>p(t,f(A))</math> approximates <math>p(t,B)</math> for all strings <math>t</math> of length less than some <math>n</math>. It is commonly considered to be one of the basic techniques for [[Information hiding\|hiding information]], often called [[steganography]].

	~~The simplest mimic functions use simple statistical models to pick the symbols in the output~~. ~~If the statistical model says~~ that ~~item <math>x</math> occurs with [[probability]] <math>p(x~~,~~A)</math>~~ and ~~item <math>y</math> occurs with probability <math>p(y~~,A)<~~/math~~>~~, then~~ a ~~random number is used~~ to ~~choose between outputting <math>x<~~/~~math> or <math>y<~~/~~math>~~ with ~~probability <math>p(x,A)</math> or <math>p(y,A)</math> respectively.~~		I woke up yesterday and realised - I've been solitary for some time today and after much bullying from buddies I now locate myself signed-up for online dating. They assured me that there are plenty of interesting, sweet and ordinary people to meet, therefore here goes the pitch!<br>My family and pals are magnificent and spending time together at tavern gigabytes or dinners is definitely a must. I haven't ever been in to clubs as I realize you [http://lukebryantickets.asiapak.net luke bryan thats my kinda night tour] can never have a decent conversation with all the sound. I likewise have two undoubtedly cheeky and really cunning dogs that are [http://www.invariablykeen.org/ invariably keen] to meet fresh individuals.<br>I strive to maintain as physically healthy as potential staying at the gymnasium several-times a week. I appreciate my athletics and make an effort to perform or watch as many a potential. I shall frequently at Hawthorn matches being winter. Note: In case that you would contemplated purchasing an athletics I don't brain, I've experienced the [http://www.Dict.cc/englisch-deutsch/carnage.html carnage] of wrestling suits [http://okkyunglee.com luke bryan concert videos] at stocktake revenue.<br><br>Look into my web blog :: [http://www.ffpjp24.org meet and Greet luke bryan]

	~~More sophisticated mimic functions use grammar-based models of <math>B</math> to structure~~ the ~~output~~. ~~One example,~~ [http://www.~~spammimic~~.~~com "SpamMimic"], uses a [[context free grammar]~~] to ~~model~~ the ~~structure of~~ a ~~typical spam email message~~. ~~It will convert the input file A~~ to ~~read like~~ a ~~spam message~~.

	~~Even more sophisticated models use reversible [[Turing machine]]s.~~

	~~==References==~~
	* Peter Wayner. [http://www.~~funet~~.fi/~~pub~~/~~crypt~~/~~old~~/~~mimic/mimic~~.~~text "Mimic Functions"~~]
	* Peter Wayner. [http://www.~~wayner~~.org~~/books/discrypt2/ "Disappearing Cryptography"~~]

	~~[[Category:Cryptography]]~~
	~~[[Category:Steganography]]~~

	~~{{Crypto-stub}}~~

en>Khazar2: /* History */clean up, typos fixed: 1930's → 1930s using AWB

2013-04-07T05:15:57Z

History: clean up, typos fixed: 1930's → 1930s using AWB

← Older revision		Revision as of 07:15, 7 April 2013
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	~~Name: Cheryl Tauchert~~<br>~~My age: 25~~<br>~~Country: France~~<br>~~Home town: Sarcelles~~ <br>~~ZIP: 95200~~<br>~~Address: 79 Rue Des Six Freres Ruellan~~<br><br>~~Feel~~ free to ~~surf~~ to ~~my web page :~~: [http://~~istoriya~~.~~sumy~~.ua/~~index.php~~/~~%D0%9A%D0%BE%D1%80%D0%B8%D1%81%D1%82%D1%83%D0%B2%D0%B0%D1%87~~:~~RogelioConstant house training dog~~]		{{inline\|date=June 2010}}

			A '''mimic function''' changes a file <math>A</math> so it assumes the statistical properties of another file <math>B</math>. That is, if <math>p(t,A)</math> is the probability of some substring <math>t</math> occurring in <math>A</math>, then a mimic function <math>f</math>, recodes <math>A</math> so that <math>p(t,f(A))</math> approximates <math>p(t,B)</math> for all strings <math>t</math> of length less than some <math>n</math>. It is commonly considered to be one of the basic techniques for [[Information hiding\|hiding information]], often called [[steganography]].

			The simplest mimic functions use simple statistical models to pick the symbols in the output. If the statistical model says that item <math>x</math> occurs with [[probability]] <math>p(x,A)</math> and item <math>y</math> occurs with probability <math>p(y,A)</math>, then a random number is used to choose between outputting <math>x</math> or <math>y</math> with probability <math>p(x,A)</math> or <math>p(y,A)</math> respectively.

			More sophisticated mimic functions use grammar-based models of <math>B</math> to structure the output. One example, [http://www.spammimic.com "SpamMimic"], uses a [[context free grammar]] to model the structure of a typical spam email message. It will convert the input file A to read like a spam message.

			Even more sophisticated models use reversible [[Turing machine]]s.

			==References==
			* Peter Wayner. [http://www.funet.fi/pub/crypt/old/mimic/mimic.text "Mimic Functions"]
			* Peter Wayner. [http://www.wayner.org/books/discrypt2/ "Disappearing Cryptography"]

			[[Category:Cryptography]]
			[[Category:Steganography]]

			{{Crypto-stub}}

en>Michael Hardy: /* History */

2012-09-01T21:22:08Z

History

New page

Name: Cheryl Tauchert My age: 25 Country: France Home town: Sarcelles ZIP: 95200 Address: 79 Rue Des Six Freres Ruellan Feel free to surf to my web page :: [http://istoriya.sumy.ua/index.php/%D0%9A%D0%BE%D1%80%D0%B8%D1%81%D1%82%D1%83%D0%B2%D0%B0%D1%87:RogelioConstant house training dog]