Gaussian network model - Revision history

en>John of Reading: Typo/general fixing, replaced: specifity → specificity (2), typo(s) fixed: , → , (2) using AWB

2014-06-28T09:24:53Z

Typo/general fixing, replaced: specifity → specificity (2), typo(s) fixed: , → , (2) using AWB

← Older revision		Revision as of 11:24, 28 June 2014
Line 1:		Line 1:
	~~{{Multiple issues\|~~		Friends call him Royal Seyler. I've usually cherished living in Idaho. To keep birds is 1 of the issues he enjoys most. The job he's been occupying for years is a messenger.<br><br>My homepage car warranty - [http://testing6.Nittanylink.com/ActivityFeed/MyProfile/tabid/60/userId/56/Default.aspx relevant web site],
	~~{{tone\|date=September 2010}}~~
	~~{{unreferenced\|date=November 2008}}~~
	}}

	~~The~~ '''Key Selection Vector''' means the numerical associated with a [[Device Key Set]] and distributed by [[Licensor]] or its designee to Adopters and used to support authentication of Licensed Products and Revocation. It is considered a confidential set of [[Key (cryptography)\|keys]] used in ~~Restricted [[Authentication]] process of the [[HDCP]]. Restricted [[authentication]] is an [[AKE]] method for devices with limited computing resources~~.
	~~This method~~ is ~~used by copying devices of any kind (such as [[DV]] recorders or [[D-VHS]] recorders) and [[Information appliance\|devices]]~~
	communicating with them for authenticating copy-one-generation and no-more-copies contents. The restricted [[authentication]] protocol employs asymmetric key management and common key cryptography and relies on the use of shared secrets and hash functions to respond to a random challenge.

	~~==Role of KSV in Restricted Authentication==~~
	This method is based on a device being able to prove that it holds a [[secret]] shared with other devices. One device authenticates another by issuing a random [[Challenge-response authentication\|challenge]] that is responded to by modifying it with the shared secrets and multiple hashings.

	During the [[authentication]] process, both parties exchange their '''KSVs'''. Then each device adds (without overflow) its own secret keys according to a '''KSV''' received from another device. If a particular bit in the vector is set to 1~~, then the corresponding secret key is used in the addition, otherwise it is ignored. For each set~~ of keys a special key called a KSV (Key Selection Vector) is created. Each KSV has exactly 20 bits set to 0 and 20 bits set to 1. Keys and '''KSVs''' are generated in such a way that during this process both devices get the ~~same 56 bit number as a result. That number is later used in the [[encryption]] process.~~

	~~==KSVs are unique to each device==~~
	~~Even valid keys can become compromised (hacked), so [[HDCP]] includes a mechanism to revoke keys~~. The KSV values are unique to each key set and, therefore, to each device. The system can then compare these values to a revocation list, and if either the transmitter or receiver appears on that list, authentication fails. Updates to the revocation list arrive with new media and are automatically integrated. So if a key set somehow does get exposed or copied, the damage can be limited.

	~~This [[revocation]] process does not affect other devices, even if the devices are of the same make and model. In that sense, '''KSV''~~' ~~values are like [[serial number]]~~s.

	~~'''Exemplification:'''~~

	''Suppose that '''Sally''' and '''Bob''' buy the same kind of [[Television\|TV]] on the same day at the same store. '''Bob''' somehow hacks his set, gets caught, and has his '''KSV''' value revoked. '''Sally''' needn't worry. Her TV has a ~~different '''KSV''' value and won't be affected in any way~~.''

	~~==Apparent KSV weaknesses==~~
	~~If we can find 40 [[Linear independence\|linearly independent]] sets of vectors (<math>A_1~~<~~/math~~>~~) keys ... (~~<~~math~~>~~A_{40}</math>)keys, say, through reverse~~-~~engineering hardware, then we can completely break the system. At that point, one can extract the secret key array for any number of KSVs he wishes.~~

	In other cases where the separate keys are not linearly independent, it is still possible to create Xkeys for any Xksv that is within the span of the (<math>A_i</math>)KSVs for which we have found the private keys. There will be, however, no guarantee of them satisfying the 20 one and 20 zero bits property.

	~~==How could this be broken?==~~
	First, it is rare to find Akeys's, Bkeys's, Aksv and Bksv that have the above property that when each device does the operation, they can both come up with the same shared secret. Therefore, this means it exists a mathematical model that creates such [~~[subsets]].~~

	~~Since the keys are generated linearly in the given [[system]], it appears that if someone could determine the Akeys [[List (computing)\|vector]] from any 40-50 different systems~~: ~~<math>A_1</math> .... <math>A_n<~~/~~math>, and knew the Xksv from system X (this is public information from the protocol), then he could determine the Xkeys private key [[array data structure\|array]].~~

	~~==What do we know?==~~
	~~If we assume that we have 40 (<math>A_i<~~/~~math>)KSVs that are linearly independent, we’ll have a set of n linear equations on 40 unknown –~~

	~~The Xkeys key vector array:~~

	~~[Xkeys] * (A1)ksv = = [(A1)keys] * Xksv[Xkeys] * (A2)ksv = = [(A2)keys] * Xksv.~~..~~[Xkeys] * (A40)ksv = = [(A40)keys] * Xksv~~

	~~By having [[Acknowledgement (data networks)\|acknowledgment]] on all the KSVs, and assuming we know the secret key [[List (computing)\|vectors]] (<math>A_i<~~/math>)keys, we can repeat the above algorithm to generate a new Bkeys for any other device with an [[arbitrary]] Bksv. Last step will be to substitute Xksv = Bksv. If the space spanned by the (<math>A_i</~~math>)KSVs doesn't span the full 40 dimensional space, we're probably OK. Either, the KSVs were designed to not span the [[space]], or we need to get the (<math>A_i<~~/~~math>)keys from a few more devices to round out the space.~~

	~~Each additional device has low odds of being [[Linear independence\|linearly dependent]] with the existing set. (roughly 1~~/~~2^[40-dimensionality-of-spanned-space]). Otherwise, this linear dependence was done on purpose. Thus, we know that all other KSVs are in the space spanned by the one we're given.~~

	Through a [[linear combination]] of any known ksv (with 20 one bits and 20 zero bits) and (A_i)keys we can construct a valid Xksv and Xkeys already know. The only trick is finding a Xksv in the subspace that has the required number of 0 & 1 [[bit]]s. This is the only potentially difficult part, though given a concrete example, it would not be difficult to solve.

	~~==See also==~~
	* [[HDCP]]
	* [[Cryptographic hash function\|Hash]] Functions

	~~==External links==~~
	* [http://~~cryptome.sabotage.org~~/~~hdcp-4attacks~~.~~htm Apparent HDCP weaknesses]~~

	~~{{DEFAULTSORT:Key Selection Vector}}~~
	~~[[Category:Digital rights management standards]~~]

en>Serensoner: /* Other relevant servers */

2013-08-07T22:30:57Z

Other relevant servers

← Older revision		Revision as of 00:30, 8 August 2013
Line 1:		Line 1:
	~~Nestor~~ is the ~~title my mothers~~ and ~~fathers~~ [~~http://pupo~~.~~ch/mypupo/panda/panda2/index~~.~~php?mod~~=~~users&action~~=~~view&id~~=~~161 auto warranty~~] ~~gave me but I don~~'~~t like when people use my complete title~~. ~~One~~ of the [~~http://www~~.~~mass~~.~~gov/ocabr/consumer-rights-~~and~~-resources/autos/lemon-laws/used-vehicle-warranty-law~~.~~html extended~~] [~~http~~://~~ghaziabadmart~~.~~com~~/~~oxwall/blogs/post/16946 car warranty] things I love most~~ is ~~greeting card collecting but I don~~'t have the ~~time recently~~. ~~Some time~~ in the ~~past I chose to live in Arizona but I need car~~ [~~http~~:/~~/www~~.~~Kbb~~.~~com~~/~~extended-auto-warranty~~/ ~~warranty~~] to ~~move~~ for ~~my family~~. ~~After extended auto warranty being out of my job for years I grew~~ to ~~become a production and distribution officer but I plan on altering it~~.<br><br>my [~~http:~~//~~Www~~.~~toyotacertified~~.~~com/warranty~~.~~html homepage -~~] [http://~~www~~.~~holzkunst-scholz~~.de/~~index~~.~~php?mod=users&action=view&id=7124 auto warranty~~]		{{Multiple issues\|
			{{tone\|date=September 2010}}
			{{unreferenced\|date=November 2008}}
			}}

			The '''Key Selection Vector''' means the numerical associated with a [[Device Key Set]] and distributed by [[Licensor]] or its designee to Adopters and used to support authentication of Licensed Products and Revocation. It is considered a confidential set of [[Key (cryptography)\|keys]] used in Restricted [[Authentication]] process of the [[HDCP]]. Restricted [[authentication]] is an [[AKE]] method for devices with limited computing resources.
			This method is used by copying devices of any kind (such as [[DV]] recorders or [[D-VHS]] recorders) and [[Information appliance\|devices]]
			communicating with them for authenticating copy-one-generation and no-more-copies contents. The restricted [[authentication]] protocol employs asymmetric key management and common key cryptography and relies on the use of shared secrets and hash functions to respond to a random challenge.

			==Role of KSV in Restricted Authentication==
			This method is based on a device being able to prove that it holds a [[secret]] shared with other devices. One device authenticates another by issuing a random [[Challenge-response authentication\|challenge]] that is responded to by modifying it with the shared secrets and multiple hashings.

			During the [[authentication]] process, both parties exchange their '''KSVs'''. Then each device adds (without overflow) its own secret keys according to a '''KSV''' received from another device. If a particular bit in the vector is set to 1, then the corresponding secret key is used in the addition, otherwise it is ignored. For each set of keys a special key called a KSV (Key Selection Vector) is created. Each KSV has exactly 20 bits set to 0 and 20 bits set to 1. Keys and '''KSVs''' are generated in such a way that during this process both devices get the same 56 bit number as a result. That number is later used in the [[encryption]] process.

			==KSVs are unique to each device==
			Even valid keys can become compromised (hacked), so [[HDCP]] includes a mechanism to revoke keys. The KSV values are unique to each key set and, therefore, to each device. The system can then compare these values to a revocation list, and if either the transmitter or receiver appears on that list, authentication fails. Updates to the revocation list arrive with new media and are automatically integrated. So if a key set somehow does get exposed or copied, the damage can be limited.

			This [[revocation]] process does not affect other devices, even if the devices are of the same make and model. In that sense, '''KSV''' values are like [[serial number]]s.

			'''Exemplification:'''

			''Suppose that '''Sally''' and '''Bob''' buy the same kind of [[Television\|TV]] on the same day at the same store. '''Bob''' somehow hacks his set, gets caught, and has his '''KSV''' value revoked. '''Sally''' needn't worry. Her TV has a different '''KSV''' value and won't be affected in any way.''

			==Apparent KSV weaknesses==
			If we can find 40 [[Linear independence\|linearly independent]] sets of vectors (<math>A_1</math>) keys ... (<math>A_{40}</math>)keys, say, through reverse-engineering hardware, then we can completely break the system. At that point, one can extract the secret key array for any number of KSVs he wishes.

			In other cases where the separate keys are not linearly independent, it is still possible to create Xkeys for any Xksv that is within the span of the (<math>A_i</math>)KSVs for which we have found the private keys. There will be, however, no guarantee of them satisfying the 20 one and 20 zero bits property.

			==How could this be broken?==
			First, it is rare to find Akeys's, Bkeys's, Aksv and Bksv that have the above property that when each device does the operation, they can both come up with the same shared secret. Therefore, this means it exists a mathematical model that creates such [[subsets]].

			Since the keys are generated linearly in the given [[system]], it appears that if someone could determine the Akeys [[List (computing)\|vector]] from any 40-50 different systems: <math>A_1</math> .... <math>A_n</math>, and knew the Xksv from system X (this is public information from the protocol), then he could determine the Xkeys private key [[array data structure\|array]].

			==What do we know?==
			If we assume that we have 40 (<math>A_i</math>)KSVs that are linearly independent, we’ll have a set of n linear equations on 40 unknown –

			The Xkeys key vector array:

			[Xkeys] * (A1)ksv = = [(A1)keys] * Xksv[Xkeys] * (A2)ksv = = [(A2)keys] * Xksv...[Xkeys] * (A40)ksv = = [(A40)keys] * Xksv

			By having [[Acknowledgement (data networks)\|acknowledgment]] on all the KSVs, and assuming we know the secret key [[List (computing)\|vectors]] (<math>A_i</math>)keys, we can repeat the above algorithm to generate a new Bkeys for any other device with an [[arbitrary]] Bksv. Last step will be to substitute Xksv = Bksv. If the space spanned by the (<math>A_i</math>)KSVs doesn't span the full 40 dimensional space, we're probably OK. Either, the KSVs were designed to not span the [[space]], or we need to get the (<math>A_i</math>)keys from a few more devices to round out the space.

			Each additional device has low odds of being [[Linear independence\|linearly dependent]] with the existing set. (roughly 1/2^[40-dimensionality-of-spanned-space]). Otherwise, this linear dependence was done on purpose. Thus, we know that all other KSVs are in the space spanned by the one we're given.

			Through a [[linear combination]] of any known ksv (with 20 one bits and 20 zero bits) and (A_i)keys we can construct a valid Xksv and Xkeys already know. The only trick is finding a Xksv in the subspace that has the required number of 0 & 1 [[bit]]s. This is the only potentially difficult part, though given a concrete example, it would not be difficult to solve.

			==See also==
			* [[HDCP]]
			* [[Cryptographic hash function\|Hash]] Functions

			==External links==
			* [http://cryptome.sabotage.org/hdcp-4attacks.htm Apparent HDCP weaknesses]

			{{DEFAULTSORT:Key Selection Vector}}
			[[Category:Digital rights management standards]]

en>DSisyphBot: r2.7.2) (Robot: Adding zh:高斯网络模型

2012-08-28T11:05:06Z

r2.7.2) (Robot: Adding zh:高斯网络模型

New page

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