© 2006 ravi sandhu secure information sharing enabled by trusted computing and pei * models ravi...

© 2006 Ravi Sandhuwww.list.gmu.edu

Secure Information Sharing Enabled byTrusted Computing and PEI* Models

Ravi Sandhu (George Mason University and TriCipher)

Kumar Ranganathan (Intel System Research Center, Bangalore)

Xinwen Zhang (George Mason University)

*PEI: Policy, Enforcement, Implementation

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Three Megatrends

Fundamental changes in• Cyber-security goals• Cyber-security threats• Cyber-security technology

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Cyber-security goals have changedCyber-security goals

• electronic commerce• information sharing• etcetera• multi-party security objectives• fuzzy objectives

INTEGRITYmodification

AVAILABILITYaccess

CONFIDENTIALITYdisclosure

USAGEpurpose

USAGE

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Cyber-security attacks have changed

The professionals have moved in• Hacking for fun and fame• Hacking for cash, espionage and sabotage

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Basic premise• Software alone cannot provide an adequate foundation for trust

Old style Trusted Computing (1970 – 1990’s)• Multics system• Capability-based computers

– Intel 432 vis a vis Intel 8086• Trust with security kernel based on military-style security labels

– Orange Book, eliminate trust from applications

What’s new (2000’s)• Hardware and cryptography-based root of trust

– Ubiquitous availability– Trust within a platform– Trust across platforms

• Rely on trust in applications– No Trojan Horses or– Mitigate Trojan Horses and bugs by legal and reputational recourse

Cyber-security technology has changed

Massive paradigm shift

Prevent information leakage by binding information to Trusted Viewers on the client

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PEI Models Framework

Security and system goals(requirements/objectives)

Target platform, e.g., TrustedComputing technology

Enforcement models

Policy models

Implementation models

NecessarilyInformal

ActualCode

Horizontalview

Looks atIndividual

layer

VerticalViewLooksAcrossLayers

Formal/quasi-formal

System blockdiagrams,

Protocol flows

Pseudo-code

Cannot do security without analyzing the application space in business terms

Cannot do security without understanding the target platform and its limitations

Divide and conquer AND confront and deal with issues at the correct layer}

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What is Information Sharing

The mother of all security problems• Share but protect

Requires controls on the client• Server-side controls do not scale to high assurance

Different from• Retail DRM (Digital Rights Management)• Enterprise DRM

Integrity of information on the client can be crypto-guaranteed to very high assurance by digital signatures. Guarantee of confidentiality on the client needs mechanisms beyond crypto alone.

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Classic Approaches to Information Sharing

Discretionary Access Control (DAC), Lampson 1971• Fundamentally broken• Controls access to the original but not to copies (or extracts)

Mandatory Access Control (MAC), Bell-LaPadula 1971• Solves the problem for coarse-grained sharing

– Thorny issues of covert channels, inference, aggregation remain but can be confronted

• Does not scale to fine-grained sharing– Super-exponential explosion of security labels is impractical– Fallback to DAC for fine-grained control (as per the Orange Book) is pointless

Originator Control (ORCON), Graubart 1989• Propagated access control lists: let copying happen but propagate ACLs to

copies (or extracts)• Park and Sandhu 2002 discuss an approach based on Trusted Viewers

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Enforcement models

Policy models


NecessarilyInformal

ActualCode

Horizontalview

Looks atIndividual

layer


Formal/quasi-formal


Protocol flows

Pseudo-code

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Scoping Information Sharing: Big Issues

Secure information sharing rather than Digital Rights Management (DRM)• Sensitivity of information content is the issue not revenue potential of retail

entertainment content• Open system as opposed to closed Enterprise DRM

Read-only versus read-write secure information sharing• Read-only is a useful subset• Avoids some of the complexities of read-write such as

– Extraction of pieces of information– Aggregation of several sources– Version control– Ability to overwrite versus annotate

Content-independent authorization versus content-dependent authorization• Content-independent is a useful subset• Content-dependent is more complex since it requires Trusted Viewers to parse

and understand the content

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Enforcement models

Policy models


NecessarilyInformal

ActualCode

Horizontalview

Looks atIndividual

layer


Formal/quasi-formal


Protocol flows

Pseudo-code

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Scoping Information Sharing

One Decomposition at the Policy Layer• Password based• Device based• Credential based

Just one possibilityDetermined by business objectives

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Scoping Information Sharing: Detailed Issues

Detailed issues include• Revocation Policy• Usage Policy• Re-dissemination Policy• Distribution Policy• Accessibility Policy

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Enforcement models

Policy models


NecessarilyInformal

ActualCode

Horizontalview

Looks atIndividual

layer


Formal/quasi-formal


Protocol flows

Pseudo-code

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Password-based encryption: traditional approach

Cleartextdocument:(O)

Encrypted document:{O}Kpw

Encryption (E) /Decryption (D)

PKCS5Password

(pw)

Kpw

Insecure due tooff-line dictionaryattacks

Guess Verify

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Trusted Viewer Seal with Password Authentication


Encrypted document:{O}K


PKCS5

Password (pw)

Seal /Unseal Encryption (E) /

Decryption (D)

K Hashed password:H(pw)

Sealed key: [K]TV

Encrypted & hashedpassword: {H(pw)}K

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Encrypted document:{O}K'


PKCS5

Password (pw)

Seal /Unseal

K

Kpw

Sealed key: [K]TV

K'

Trusted Viewer Seal with Password Authentication and Encryption

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Seal /Unseal

K

Sealed key:[{K}PubK_Dev]TV

Encryption /Decryption

PubK_Dev PrivK_Dev

Trusted Viewer Seal with Device Encryption

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Trusted Viewer Seal with Credential Authentication


Encrypted credentialpolicy

CredentialPolicy

Credentialproof

Compare




Seal /Unseal

K

Sealed key: [K]TV

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Trusted Viewer Seal with Credential Encryption




Seal /Unseal

K

Sealed key:[{K}PubK_Cred]TV

Encryption /Decryption

PubK_Cred PrivK_Cred

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Enforcement models

Policy models


NecessarilyInformal

ActualCode

Horizontalview

Looks atIndividual

layer


Formal/quasi-formal


Protocol flows

Pseudo-code

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Trusted Viewer Seal with Password Authentication




PKCS5

Password (pw)

Seal /Unseal Encryption (E) /

Decryption (D)

K Hashed password:H(pw)

Sealed key: [K]TV

Encrypted & hashedpassword: {H(pw)}K

On-line password guessingNeed a throttling mechanismMany possibilities


Secure Information Sharing Enabled byTrusted Computing and PEI* Models

Ravi Sandhu (George Mason University and TriCipher)

Kumar Ranganathan (Intel System Research Center, Bangalore)

Xinwen Zhang (George Mason University)

*PEI: Policy, Enforcement, Implementation

Questions ??

© 2006 ravi sandhu secure information sharing enabled by trusted computing and pei * models ravi...

Documents

content slide

client slide

sabotage slide

implementation slide

scoping information

secure information sharing

pei models framework

password authentication