Total ionic strength adjustment buffer - Revision history

en>Colonies Chris: /* Theory */

2014-04-11T20:40:07Z

Theory

← Older revision		Revision as of 22:40, 11 April 2014
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en>ChrisGualtieri: /* Theory */Checkwiki 61 + General Fixes using AWB

2014-02-22T05:26:00Z

Theory: Checkwiki 61 + General Fixes using AWB

← Older revision		Revision as of 07:26, 22 February 2014
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	~~{{About\|a security policy model\|the Buddhist concept\|Noninterference (Buddhism)}}~~		Greetings! I am Myrtle Shroyer. Playing baseball is over the counter std test - [http://nuvem.tk/altergalactica/AliceedMaurermy read more], hobby he will by no means quit doing. North Dakota is where me and my spouse live. Managing people is what I do and the wage has been really fulfilling.

	~~'''Non-interference''' is a strict [[multilevel security]] policy model, first described by Goguen and Meseguer in 1982, and amplified further in 1984~~.

	~~==Introduction==~~
	~~In simple terms, a computer~~ is modeled as a machine with inputs and outputs. Inputs and outputs are classified as either ''low'' (low sensitivity, not highly classified) or ''high'' (sensitive, not to be viewed by uncleared individuals). A computer has the ~~non~~-~~interference property if and only if any sequence of low inputs will produce the same low outputs, regardless of what the high level inputs are.~~

	That is, if a low (uncleared) user is working on the machine, it will respond in exactly the same manner (on the low outputs) whether or not a high (cleared) user is working with sensitive data. The low user will not be able to acquire any [~~[information]] about the activities (if any) of the high user.~~

	~~==Formal expression==~~

	Let <math>M</math> be a memory configuration, and let <math>M_L</math> and <math>M_R</math> be the projection of the memory <math>M</math> to the low and high parts, respectively. Let <math>{=_L}</math> be the function that compares the low parts of the memory configurations, i.e., <math>M\ {=_L}\ M^\prime</~~math> iff <math>M_{L} = M_{L}^\prime<~~/~~math>~~. ~~Let <math>(P,M) \rightarrow^* M^\prime</math> be the execution of the program <math>P<~~/~~math> starting with memory configuration <math>M<~~/~~math> and terminating with the memory configuration <math>M^\prime</math>.~~

	The definition of non-interference for a deterministic program <math>P</math> is the following:<ref>Smith, Geoffrey (2007). "Principles of Secure Information Flow Analysis". Advances in Information Security. 27. Springer US. pp. 291-307.</ref>

	~~<math>\begin{array}{rrl}\forall M_1, M_2 :\; & M_1\ {=_L}\ M_2 & \land\\~~
	~~& (P,M_1) \rightarrow^* M_1^\prime & \land\\~~
	~~&(P,M_2) \rightarrow^* M_2^\prime &\Rightarrow\\~~
	~~&M_1^\prime\ {=_L}\ M_2^\prime\end{array}</math>~~

	~~==Limitations==~~

	~~===Strictness===~~
	~~This is a very strict policy, in that a computer system with [[covert channels~~]~~] may comply with~~, ~~say, the [[Bell–LaPadula model]], but~~ will not comply with non-interference. The reverse could be true (under reasonable conditions, being that the system should have labelled files, etc.) except for the "No classified information at startup" exceptions noted below. However, non-interference has been shown to be stronger than [[non-deducibility]].

	~~This strictness comes with a price. It~~ is very difficult to make a computer system with this property. There may be only one or two commercially available products that have been verified to comply with this policy, and these would essentially be as simple as switches and ~~one-way information filters (although these could be arranged to provide useful behaviour)~~.

	~~===No classified information at startup===~~
	~~If the computer has (at time=0) any high (i.e., classified) information within it, or low users create high information subsequent to time=0 (so-called "write-up," which~~ is allowed by many computer security policies), then the computer can legally leak all that high information to the low user, and can still be said to comply with the non-interference policy. The low user will not be able to learn anything about high user activities, but can learn about any high information that was created through means other than the actions of high users.(von Oheimb 2004)

	~~Computer systems that comply with the Bell-LaPadula Model~~ do not suffer from this problem since they explicitly forbid "read-up." Consequently, a computer system that complies with non-interference will not necessarily comply with the Bell-LaPadula Model. Thus, the [[Bell–LaPadula model]] and the ~~non-interference model are incomparable: the Bell-LaPadula Model is stricter regarding read-up, and the non-interference model is stricter with respect to [[covert channels]]~~.

	~~===No summarisation===~~
	Some legitimate multilevel security activities treat individual data records (e.g., personal details) as sensitive, but allow statistical functions of the data (e.g., the mean, the total number) to be released more widely. This cannot be achieved with a non-interference machine.

	~~==References==~~
	~~{{reflist}}~~

	~~==Further reading==~~

	* {{cite encyclopedia
	~~\| last = McLean~~
	~~\| first = John~~
	~~\| title = Security Models~~
	~~\| encyclopedia = Encyclopedia of Software Engineering~~
	~~\| volume = 2~~
	~~\| pages = 1136–1145~~
	~~\| publisher = John Wiley & Sons, Inc~~
	~~\| location = New York~~
	~~\| year = 1994 }}~~

	* {{cite conference
	~~\| first = David~~
	~~\| last = von Oheimb~~
	~~\| authorlink = David von Oheimb~~
	~~\| title = Information Flow Control Revisited: Noninfluence = Noninterference + Nonleakage~~
	~~\| booktitle = European Symposium on Research in Computer Security (ESORICS)~~
	~~\| pages = 225–243~~
	~~\| publisher = LNCS, Springer-Verlag~~
	~~\| year = 2004~~
	~~\| location = Sophia Antipolis, France}}~~

	~~{{DEFAULTSORT:Non-Interference (Security)}}~~
	~~[[Category:Computer security models]]~~

206.239.34.25: /* Theory */ grammar

2013-09-06T21:59:59Z

Theory: grammar

← Older revision		Revision as of 23:59, 6 September 2013
Line 1:		Line 1:
	~~Nice to meet you, my name~~ is [~~http://Www~~.~~Bettertoknow~~.~~org.au/bugs/mensbusiness/GenitalAnalHerpes Figures Held] although I don~~'~~t really like becoming known as like that~~. ~~California is where I've usually been residing~~ and ~~I love every working day residing here~~. ~~Bookkeeping~~ is ~~her~~ working ~~day occupation now. His wife doesn't like~~ it the ~~way he does but what he truly likes doing home std test~~ is to ~~do aerobics~~ and ~~he's been performing it for fairly [http:~~//~~payiz~~.az/~~index~~.~~php?do~~=/~~profile-14379~~/~~info~~/ ~~at home std testing] home [http:~~//~~www.justmommies.com~~/~~articles/sexually_transmitted_disease~~.~~shtml std testing]~~ a ~~while.~~<br><br>~~Visit my web site std [http~~:~~//www~~.~~streaming~~.~~iwarrior~~.~~net~~/~~blog~~/~~396549 home std test kit~~] ~~test~~ ([~~http://www~~.~~kindrasdesigns~~-~~testing~~.~~com/index~~.~~php?~~do~~=/profile~~-~~12578/info/ simply click~~ the up ~~coming website page~~])		{{About\|a security policy model\|the Buddhist concept\|Noninterference (Buddhism)}}

			'''Non-interference''' is a strict [[multilevel security]] policy model, first described by Goguen and Meseguer in 1982, and amplified further in 1984.

			==Introduction==
			In simple terms, a computer is modeled as a machine with inputs and outputs. Inputs and outputs are classified as either ''low'' (low sensitivity, not highly classified) or ''high'' (sensitive, not to be viewed by uncleared individuals). A computer has the non-interference property if and only if any sequence of low inputs will produce the same low outputs, regardless of what the high level inputs are.

			That is, if a low (uncleared) user is working on the machine, it will respond in exactly the same manner (on the low outputs) whether or not a high (cleared) user is working with sensitive data. The low user will not be able to acquire any [[information]] about the activities (if any) of the high user.

			==Formal expression==

			Let <math>M</math> be a memory configuration, and let <math>M_L</math> and <math>M_R</math> be the projection of the memory <math>M</math> to the low and high parts, respectively. Let <math>{=_L}</math> be the function that compares the low parts of the memory configurations, i.e., <math>M\ {=_L}\ M^\prime</math> iff <math>M_{L} = M_{L}^\prime</math>. Let <math>(P,M) \rightarrow^* M^\prime</math> be the execution of the program <math>P</math> starting with memory configuration <math>M</math> and terminating with the memory configuration <math>M^\prime</math>.

			The definition of non-interference for a deterministic program <math>P</math> is the following:<ref>Smith, Geoffrey (2007). "Principles of Secure Information Flow Analysis". Advances in Information Security. 27. Springer US. pp. 291-307.</ref>

			<math>\begin{array}{rrl}\forall M_1, M_2 :\; & M_1\ {=_L}\ M_2 & \land\\
			& (P,M_1) \rightarrow^* M_1^\prime & \land\\
			&(P,M_2) \rightarrow^* M_2^\prime &\Rightarrow\\
			&M_1^\prime\ {=_L}\ M_2^\prime\end{array}</math>

			==Limitations==

			===Strictness===
			This is a very strict policy, in that a computer system with [[covert channels]] may comply with, say, the [[Bell–LaPadula model]], but will not comply with non-interference. The reverse could be true (under reasonable conditions, being that the system should have labelled files, etc.) except for the "No classified information at startup" exceptions noted below. However, non-interference has been shown to be stronger than [[non-deducibility]].

			This strictness comes with a price. It is very difficult to make a computer system with this property. There may be only one or two commercially available products that have been verified to comply with this policy, and these would essentially be as simple as switches and one-way information filters (although these could be arranged to provide useful behaviour).

			===No classified information at startup===
			If the computer has (at time=0) any high (i.e., classified) information within it, or low users create high information subsequent to time=0 (so-called "write-up," which is allowed by many computer security policies), then the computer can legally leak all that high information to the low user, and can still be said to comply with the non-interference policy. The low user will not be able to learn anything about high user activities, but can learn about any high information that was created through means other than the actions of high users.(von Oheimb 2004)

			Computer systems that comply with the Bell-LaPadula Model do not suffer from this problem since they explicitly forbid "read-up." Consequently, a computer system that complies with non-interference will not necessarily comply with the Bell-LaPadula Model. Thus, the [[Bell–LaPadula model]] and the non-interference model are incomparable: the Bell-LaPadula Model is stricter regarding read-up, and the non-interference model is stricter with respect to [[covert channels]].

			===No summarisation===
			Some legitimate multilevel security activities treat individual data records (e.g., personal details) as sensitive, but allow statistical functions of the data (e.g., the mean, the total number) to be released more widely. This cannot be achieved with a non-interference machine.

			==References==
			{{reflist}}

			==Further reading==

			* {{cite encyclopedia
			\| last = McLean
			\| first = John
			\| title = Security Models
			\| encyclopedia = Encyclopedia of Software Engineering
			\| volume = 2
			\| pages = 1136–1145
			\| publisher = John Wiley & Sons, Inc
			\| location = New York
			\| year = 1994 }}

			* {{cite conference
			\| first = David
			\| last = von Oheimb
			\| authorlink = David von Oheimb
			\| title = Information Flow Control Revisited: Noninfluence = Noninterference + Nonleakage
			\| booktitle = European Symposium on Research in Computer Security (ESORICS)
			\| pages = 225–243
			\| publisher = LNCS, Springer-Verlag
			\| year = 2004
			\| location = Sophia Antipolis, France}}

			{{DEFAULTSORT:Non-Interference (Security)}}
			[[Category:Computer security models]]

70.189.170.229: improve

2011-04-21T16:37:08Z

improve

New page

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