Internet Engineering Course Semantic Web, Web Services, Semantic Web Services 1.
Semantic Web - Sharif University of...
Transcript of Semantic Web - Sharif University of...
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Semantic Web
Morteza Amini
Semantic Web Security
Sharif University of Technology Fall 95-96
Outline
Information Security and Semantic Web
Security Ontology and Its Application
Access Control in Semantic Web
Trust in Semantic Web
Privacy in Semantic Web
Sharif Univ. of Tech. Semantic Web Security - Morteza Amini 2
Outline
Information Security and Semantic Web
Security Ontology and Its Application
Access Control in Semantic Web
Trust in Semantic Web
Privacy in Semantic Web
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Information Security Concepts
Information Security is based on CIA.
Confidentiality: Protecting the information from disclosure to
unauthorized parties.
Integrity: The trustworthiness of data or resources, it’s usually
phrased in terms of preventing improper or unauthorized
modification.
Availability: Ensuring that authorized parties are able to access
the information when needed.
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Current Web Security
Semantic Web Security - Morteza Amini
User
Web server
HTML Documents
HTTP Request
HTTP Response
AAA: Authentication, Authorization, Accounting
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Semantic Web Security
We need to provide security for three types of entities in
Semantic Web:
Web Resources
Agents
Web Services
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Semantic Web Security (Cont.)
Entities can be one of 3 types:
Private -- No other entity has the right to access a private service/agent/resource
Secure -- Only entities that satisfy the associated policy of the secure agent/service/resource have the right to access it
Open -- All entities have the right to access an open resource/service/agent
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Current Web Security
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User
Semantic Web Server
Semantic Web Resources
Agent
Request for resource
Resource
Other Services
Automatic conversation! What can we do? Where and How can apply security in S.W.?
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The Semantic Web Layer Cake
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Security in Different Layers
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Outline
Information Security and Semantic Web
Security Ontology and Its Application
Access Control in Semantic Web
Trust in Semantic Web
Privacy in Semantic Web
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Security Ontology
Using ontology for specification of Core elements and concepts of security systems Security requirements of users and agents Security capabilities of systems Security policies Objects which are under protection ....
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Security Ontology Sample
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Merging with Service Profile in DAML-S
(similarly in OWL-S)
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Security Ontology Sample (Cont.)
Credentials Ontology
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Security Ontology Sample (Cont.)
Credentials Ontology
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Some Application of Security Ontology
Formal specification of security requirements/policies for Service/Agent/Web Resource
Formal reasoning about security
Matchmaking of services w.r.t. security requirements: General Match Close Match Possibility of Negotiation No Match
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Agent Service This is my Credential
No Match with my Credential Requirements
I’m sorry
They can speak
about security
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Outline
Information Security and Semantic Web
Security Ontology and Its Application
Access Control in Semantic Web
Trust in Semantic Web
Privacy in Semantic Web
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Access Control
Access Control Model characterizes the rights of each subject (active entity, such as a process) with respect to every other entity.-- [Matt Bishop, 2003]
Some kinds of Access Control Models: DAC (Discretionary Access Control) MAC (Mandatory Access Control) RBAC (Role-Based Access Control) ABAC (Attribute-Based Access Control)
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DAC & MAC Models
Objects (O): The set of all protected entities
Subjects (S): The set of active objects, such as processes and users
Rights (R): The set of possible access rights (actions) of subjects on objects.
DAC (Discretionary Access Control): The owner of the information can define permissions on information (in an access matrix)
MAC (Mandatory Access Control): restricting access to objects based on the sensitivity (as represented by a label) of the information contained in the objects and the formal authorization (i.e., clearance) of subjects to access information of such sensitivity.
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Right Objects Subjects O1 O2
S1 + -
S2 - +
B
Secret
Very Confidential
Confidential
Unclassified
s
A
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Role-Based Access Control (RBAC)
Role-Based Access [Ferraiolo et al, 2003] is similar to DAC except that instead of identifying a particular user, an access policy is created to allow users of a particular class (i.e. those who play some “role”) to access objects.
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Roles Subjects R1 R2
S1
S2
Right Objects Roles O1 O2
R1 + -
R2 - +
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Efforts on Access Control in S.W.
Some efforts were done to extend security mechanisms applicable to distributed systems (e.g. Kerberos, PKI, SPKI, etc.) for the semantic web.
Two kinds of Access Control Approach for S.W.: Identity-Based (Traditional Approach)
Attribute(Credential)-Based or Rule-Based or Policy-Based (New Approach) Each resource has its own access policies
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Authentication & Identification
Associate Group or Role to Identity
Retrieve Permissions of Group or Role
Fire Access Policy based on Credential
Retrieve Permissions from Access Policy
Reasoning to achieve Needed Credential
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Advantages of Rule based Access Control
Can specify dynamic policy rules in order to dynamically change the system security management
Offer maximum freedom and heterogeneity of the components
Can be used to force other security aspects such as Privacy, Obligations, ....
Able to define fine-grained access policies (on individual URIs to instances and classes)
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Access Control Challenges in SW
Policy specification in conceptual or individual layer
Fine-grained access control in open environment
Security permissions inheritance (policy propagation) Super Class and Sub Class Property and Sub Property Subsumption, Union, Intersection Restriction
Decentralized access data (policies)
Detection and resolution of conflicts between explicit and implicit policies
Policy composition (e.g., in service composition)
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Access Control Models in Semantic Web
W3C ACL - 2004
FGAC: Damiani, et al. - 2002
Rei: Kagal, et al. - 2003
KAoS: Uszok, et al. - 2003
SAIE: Abolhassani, et al. - 2003
SBAC: Javanmardi, et al. - 2006
SAC: Yague, et al. - 2005
SBAC: Naumenko – 2007
MA(DL)2: Amini, et al - 2010
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W3C ACL System
Goals: ACLs are designed to express access rules in a logical, unambiguous, machine-accessible format.
Structure: An access system may be divided into: Identity Management
Maintaining identity information. HTTP basic authentication credentials are a form of identity, as are the client machine's IP address and any SSL identity held by the user of that machine.
Group Association Lists of which identities and groups lie within which other groups.
Privilege Management Associating resources or groups of resources with access privileges
and lists of groups or identities enables the resource holder.
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W3C ACL System (Cont.)
Semantic Web Implication: A reasonable semantic web query for determining an identity's access privileges would be, for a given resource: Find the ACL rules for that resource. Find all the groups in that ACL. Find all the users in those groups. See if the caller's identity is among them.
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(namespace '(a http://localhost/SqlDB# myDb local:/) attach '(\"W3C::Rdf::SqlDB\" (\"properties:/usr/local/perl/modules/Conf/chacl.prop\" \"name:myDb::W3Cacls\")) ask '(myDb::W3Cacls (a::accessTo ?acl http://www.w3.org/Member/Overview.html) (a::access ?acl a::GET) (a::memberOf ?groups \"eric\") (a::accessor ?acl ?groups) ) collect '(?groups ?acl) )
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W3C ACL System (Cont.)
ACL Database Schema
uris (id, uri, acl) Associates a uri with a combincation of acls.
acls (acl, id, access) Unique combinations of ACL rules
hierarchy (sub, super, sponsor, stops) Associate identities or groups to groups
idInclusions (id, groupId, generation) Maintains the transitive closure of hierarchy
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FGAC: Fine-Grained Access Control
FGAC [E. Damiani, 2000-2002]
Fine-grained access control based on XML structure
An access rule could be applied locally or propagated recursively based on XML hierarchy
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{ }{ }
Access Authorization: , , , , is identified by URI or XPath
,
,
subject object action sign typeobjectsign
type local recursive
∈ + −
∈
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Policy based Security in Semantic Web
Policy specification languages for Semantic Web
Ponder [Damianou, et. al., 2000] KAoS [Bradshaw, Uszok, e. al., 2001-2003]
Developed in Institute for Human and Machine Cognition (IHMC), Univ.
Rei [Kagal, Finin, et. al., 2002-2003]
Developed in UMBC
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Based on Ontology Languages
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Types of Security Policy for S.W.
Policy language can cover following types of security policies for semantic web security.
Access Policies: policies about accessing web entities Delegation Policies Refrain Policies Obligation Policies
Privacy Policies: policies about accessing user’s private information
Conversation Policies: policies about S.W. entities conversation (security requirements for conversation)
Meta Policies: policies about policies Policy Priority policies Policy Harmonization Policies
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KAoS P.L. based System
KAoS Core Ontology (KPO): Rely on DAML DL-based ontology of the computational
environment Defines basic ontologies for actions, actors, groups, places,
various entities related to actions (e.g. computing resources), and policies
Supports following types of policies: Authorization Encryption Access and Resource Control Various forms of Obligation Agent Conversation Mobility Domain Registration
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Just for Security
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Example Policy Using KAoS P.L.
Members of domain called Arabello-HQ are forbidden to communicate with the outside of this domain using unencrypted communication.
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KAoS Policy Conflict Resolution
Authorization Policy: Authorized or Forbidden to do some actions
Obligation Policy: Required or Not-Required to do some actions
Types of policy conflict:
Positive vs. Negative Authorization:
Being simultaneously permitted and forbidden from performing some actions.
Positive vs. Negative Obligation:
Being both required and not required to perform
some action.
Positive Obligation vs. Negative Authorization:
Being required to perform a forbidden action.
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KAoS Policy Conflict Resolution (Cont.)
Policy precedence conditions: is needed to properly execute the automatic conflict resolution. Some conditions are: Priority Update Time: New policies have higher priority Relative authorities of individual who defined or imposed a policy The Scope of Policy: Subdomains takes precedence over superdomains
or vise versa
Steps in policy conflict resolution using Stanford’s Java Theorem Prover (JTP): Sort policies based on user-defined criteria. For each policy check the conflict with policies with lower priority. Remove the lower priority policy from the conflicting pair of policies. Do harmonization. It may generate zero, one or several new policies to
replace the removed policy. The newly policies inherit the precedence and the time of last update
from the removed policy.
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Policy Harmonization
If P1 and P4 are two Cartesian products defined as: P1 = D11 x D12 x …. x D1n P4 = D41 x D42 x …. x D4n
then P1\P4 = subP1 ∪ subP2 ∪ … ∪ subPn
where subPk = (D11 ∩ D41) x ... x (D1(k-1) ∩ D4(k-1)) x (D1k \ D4k) x D1(k+1) x .. x D1n
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KAoS Policy Administration Tool (KPAT)
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Rei: A Policy Language
A declarative policy language for describing policies over actions
Represented in RDF-S + logic like variables
Based on deontic concepts and speech acts
Possible to write Rei policies over ontologies in other semantic web languages
Different kinds of policies Security, privacy, conversation, etc.
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Delegation Revocation Request Cancel
Right Prohibition Obligation Dispensation
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Deontic Concepts & Speech Acts
Deontic Logic Concepts: can be used to describe properties of agents domain specific conditions in terms of: Right (Permission): What an agent can do Prohibition: What an agent can not do Obligation: What an agent should do Dispensation: What an agent need no longer do
Speech Acts: can be used to extend the policies Delegation: Add a permission Revocation: Remove a permission or add a prohibition Request: Causes an action to be performed or causes a delegation
which leads to a permission Cancel: Cancels previous request
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Rei Specifications
Policy Properties: Context, Default Policy, Grants
Deontic objects Rights, Prohibitions, Obligations, Dispensations Properties : Actor, Action, Constraints
Actions Properties: Actor, Target objects, PreConditions, Effects Composite actions: Seq, Choice, Once, Repetition
Speech Acts Delegation, Revocation, Request, Cancel Properties: Sender, Receiver, Deontic object/Action Used to modify policies
Meta Policies Setting priorities between policies or rules Setting modality precedence
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Rei Example Policy
All graduate students have the right to delegate a printing action on the HPPrinter in SUT to any undergraduate student
Logic Right(Grad, delegate(UnderGrad, right(print(sut-hpprinter))),
Constraints). Constraints = student(Grad, graduateStudent), student(UnderGrad, undergraduateStudent)
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Rei Example Policy (Cont.)
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:policy a rei:Policy; rei:grants [a rei:granting; rei:to s; rei:deontic R; rei:oncondition [a rei:SimpleCondition; rei:subject s; rei:predicate rdf:type; rei:object univ:GradStudent]
:s a rei:Variable.
:r a rei:Variable.
:R a rei:Right;
rei:agent rei:s;
rei:action [a rei:Delegate;
rei:Sender s; rei:Receiver r;
rei:Content [ a univ:PrintingAction;
rei:target sut:HPPrinter];
rei:constraints[a rei:SimpleCondition;
rei:subject r;
rei:predicate rdf:type;
rei:object univ:UndergradStudent].
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Security Aware Inference Engine
SAIE [Abolhassani, et al. – 2005]
Add Security at the level of inference engine
Security model is described by D.L.
We need to add security check in tableau algorithm
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Security Aware Inference Engine
Adding security semantics to expansion rules of Tableau Algorithm
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Security Aware Inference Engine
Security added Tableau Algorithm: This algorithm works based on expansion (completion) rules A tree is expanded starting from the original statement (i.e.
Query) A branch closes
in case of clash (i.e. C and ~C in the same node) in case of “security violation”
Algorithm terminates if no completion rule is applicable
It can infer security policies for complex concepts from the primitive ones; however, cannot infer the vice versa.
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SBAC: Semantic Based Access Control
SBAC [Javanmardi, Amini 2006]
Conceptual (Ontology) Level Access Control Based on the ontology of subjects, objects, and actions Reducing all semantic relationships to the subsumption Access rule propagation based on subsumption relationships in
subject, object, and action domains.
Semantic Web Security - Morteza Amini
{ }{ }{ }( ){ }{ }
, ,
, , , , , , , , ,
, ,
, ,Re
C T A R A R
SBAC OB AB Opr
OB Ont Ont SO Ont OO Ont AO
Ont C T R A
AB s o a s SO o OO a AO
Opr CA Grant voke
σ σ
=
= = ∨ = ∨ =
= ≤ ≤ ≤ ≤
= ± ∈ ∧ ∈ ∧ ∈
=
( ) ( )( ) ( )( ) ( )( ) ( )
Subjects Domain: , , , , ,
Objects Domain: , , , , ,
, , , , ,Actions Domain:
, , , , ,
i j i j
i j i j
i j i j
j j i i
s o a s s s o a
s o a o o s o a
s o a a a s o a
s o a a a s o a
± ∧ ≤ → ±
± ∧ ≤ → ±
+ ∧ ≤ → +
− ∧ ≤ → +
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MA(DL)2 Authorization Model
MA(DL)2 [Amini et al. – 2010]
An access control model based on MA(DL)2 Logic MADL: Multi-Agent Deontic Logic DL: Description Logic
Specification of ontology of subjects, objects, and actions using DL.
Policy specification and inference using MA(DL)2 logic
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MA(DL)2 Authorization Model
Policy specification in two levels: Conceptual level and ground (individual) level
Types of policies: Permissions, Prohibitions, Obligations
Sample Policy for conceptual level: Visiting professors and students in CE can access CE’s resources
except theses. True → PE(authCE@CE)do((Student⊔ExtFacultyMember)⊓Visitor, ⊤Object \Thesis, Read)
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Outline
Information Security and Semantic Web
Security Ontology and Its Application
Access Control in Semantic Web
Trust in Semantic Web
Privacy in Semantic Web
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What is Trust?
An entity is trustworthy if there is sufficient credible evidence leading one to believe that the system will meet a set of given requirements.
Trust is a measure of trustworthiness, relying on the evidence provided.
Central Questions in S.W.: How trustworthy is information found on the Semantic Web? How do I decide that it is trustworthy?
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Basic Roles
Information Providers want that their information is used / believed might want to state their publishing intend (assertion, quote) are only willing to put a certain effort into publishing
Information Consumers want to use the information for different tasks have different subjective trust requirements have different subjective preferences for certain trust
mechanisms
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Trust Mechanisms
Reputation-based Trust Mechanisms
Context-based Trust Mechanisms
Content-based Trust Mechanisms
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Reputation-based Trust Mechanisms
Include rating systems and web-of-trust mechanisms
Are a well researched area
Have a general problem: They require explicit and topic-specific trust ratings high effort for information consumers
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Context-based Trust Mechanisms
Use background information about the information provider e.g. his role in the application domain or his membership in a
specific group example policies: "Distrust everything a vendor says about his
competitor“ or “Trust all members of organization A.”
Information created in the information gathering process publishing and retrieval date and the retrieval URL information whether a signature is verifiable or not example policy: “Trust all information which has been signed
and is not older than a month.”
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Content-based Trust Mechanisms
Use information content itself, together related information content published by other information providers.
Example policies: “Believe information which has been stated by at least 5
independent sources.” “Distrust product prices that are more than 50% below the
average price.” “Distrust people claiming that Texan cows are aliens.”
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Requirements for a Semantic Web Trust Layer
Use of all trust relevant information available: Journalism’s WWWWW: who, what, where, when and why
Support different, subjective, task-specific trust policies Reputation-based Context-based Content-based
Keep in mind that many applications don’t require total trustworthiness.
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Trust based on:
Digital Signatures XML Signature
W3C Candidate Recommendation (October 2000) Joint work with IETF
Develop a XML syntax used for representing signatures on digital content and procedures for computing and verifying such signatures.
XML Encryption Developing a process for encrypting/decrypting digital content
(including XML documents and portions thereof) an XML syntax used to represent the
(1) encrypted content and (2) information that enables an intended recipient to decrypt it.
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Outline
Information Security and Semantic Web
Security Ontology and Its Application
Access Control in Semantic Web
Trust in Semantic Web
Privacy in Semantic Web
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Platform for Privacy Preferences (P3P)
Concerns about privacy of personal data on the Web
Platform for Privacy Preferences (P3P) candidate recommendation (December 2000).
Allows: Web service providers to make a formal statement of their
privacy policies. Users to set their privacy preferences manual or automatic comparison of preferences against policy.
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Goals and Capabilities of P3P1.0
P3P version 1.0: A protocol designed to inform Web users of the data-collection practices of Web sites.
It provides a way for a Web site to encode its data-collection and data-use practices in a machine-readable XML format known as a P3P policy.
The P3P specification defines: A standard schema for data a Web site may wish to collect, known as
the "P3P base data schema" A standard set of uses, recipients, data categories, and other privacy
disclosures An XML format for expressing a privacy policy A means of associating privacy policies with Web pages or sites, and
cookies A mechanism for transporting P3P policies over HTTP
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Goals of P3P1.0
The goal of P3P version 1.0 is twofold:
It allows Web sites to present their data-collection practices in
a standardized, machine-readable, easy-to-locate manner.
It enables Web users to understand what data will be collected by sites they visit, how that data will be used, and what data/uses they may "opt-out" of or "opt-in" to.
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References
“Computer Security, Art and Science”, Matt Bishop, Addison-Wesley, 2003
“Towards security and trust management policies on the Web”, Theo Dimitrakos, Brian Matthews, Juan Bicarregui, CLRC Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK.
“A Semantic Approach for Access Control in Web Services”, Mariemma I. Yagüe, José M. Troya, EUroWeb 2002.
“Agents, Trust, and Information Access on the Semantic Web”, Timothy Finin and Anupam Joshi, ACM SIGMOD, December 2002.
“KAoS Policy and Domain Services: Toward a Description-Logic Approach to Policy Representation, Deconfliction, and Enforcement”, A. Uszok, J. Bradshaw, R. Jeffers, N. Suri, P. Hayes, M. Breedy, L. Bunch, M. Johnson, S. Kulkarni, J. Lott.
“W3C ACL System”, Eric Prud'hommeaux, http://www.w3.org/2001/04/20-ACLs.html, 2001.
“W3C recommendations for privacy, security, trust”, Brian Matthews, W3C UK Office at RAL, http://www.nr.no/coras/workshop_at_RAL/w3coffice-bmm.ppt, March 2002.
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References (Cont.)
“A Policy Based Approach to Security for the Semantic Web”, Lalana Kagal, Tim Finin, Anupam Joshi, ISWC2003.
“Security for DAML Web Services: Annotation and Matchmaking”, Grit Denker, Tim Finin, Lalana Kagal, Massimo Paolucci, Katia Sycara, ISWC2003.
“Creating a Policy-Aware Web: Discretionary, Rule-based Access for the World Wide Web”, Weitzner, Daniel, Hendler, James, Berners-Lee, Tim and Connolly, Dan. In Web and Information Security, 2004.
“Security in Semantic Web”, Hassan Abolhassani, Leila Sharif, 2004.
“The Platform for Privacy Preferences 1.0 (P3P1.0) Specification”, http://www.w3.org/TR/P3P, April 2002.
“The Semantic Web Trust Layer”, Jeremy Carroll, Christian Bizer, Developers Day Talk at The Thirteenth International World Wide Web Conference (WWW2004), New York, May 2004.
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Any Question... [email protected]
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