Secure Group Communication Related Issues Presenter: Haiyan Cheng - - PowerPoint PPT Presentation

1 CS 6204, Spring 2005

Secure Group Communication Related Issues

Presenter: Haiyan Cheng

2 CS 6204, Spring 2005

Outlines

♦ Addresses relevant security issues for IP

multicast network

♦ Investigates steps to create secure multicast

sessions

– Group membership – Key distribution

♦ Establishes a criteria to evaluate multicast

keying architectures.

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Characteristics of Multicast

♦ Efficient data distribution ♦ Dynamic group membership ♦ Vulnerable to attack

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Security Services for Multicast

♦ Defining multicast by Access Control

during registration

♦ Key management

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Threats to Multicast Communications

♦ Eavesdropping ♦ Unauthorized creation of data ♦ Unauthorized alteration of data ♦ Unauthorized destruction of data ♦ Denial of service ♦ Illegal use of data

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Fundamental Security Services

♦ Authentication—Assure host identity (only

authorized hosts are permitted to join the secure group)

♦ Integrity—Assure traffic not altered ♦ Confidentiality—Assure information

confidentiality

– Encryption – Limiting the routing of session IP datagrams

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Implementation Details

♦ Initiator defines session requirements ♦ Initiator announces requirements to

potential participants

– Advertisement with SAP (Session Announcement Protocol) – Invitation with SIP (Session Initiation Protocol)

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Implementation Details

♦ Type of cryptographic algorithm ♦ Length of a crypto-period ♦ Key length ♦ Type of authentication mechanism used ♦ Other security related information

describing the implementation details of a particular secure session

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Key Management Issues

♦ Key management ♦ Key distribution ♦ Access control for key material

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Secure Multicast Process

1.

Identify need for a secure session

2.

Initiator defines the parameters

3.

Initiator determines whether assistant is required to perform the participant registration or key distribution functions.

4.

Announce session description to potential participants

5.

Potential participant register for the secure session

6.

Necessary maintenance operation can be performed during the course of a secure session.

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Secure Multicast Criteria

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Key Distribution Architectures

♦ Manual Key Distribution ♦ Pairwise Keying ♦ Hierarchical trees ♦ Secure Lock ♦ Distributed Registration and Key

Distribution (DiRK)

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Key Distribution Architectures

♦ Manual Key Distribution

– Key generation and distribution functions are reside at a central KDC (Key Distribution Center). – Key material must be determined by the initiator in advance. – No computational load on individual participants. – Not scalable. – Slow response to dynamic user entries and exits from the secure multicast group. – New key material must be manually distributed to valid participants in case there’s a group key compromise.

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Key Distribution Architectures

♦ Pairwise Keying

– CBT (Core Base Tree) architecture (proposed by Ballardie)

• Initiator creates an Access Control List (ACL) and SA

(Security Association)

• ACL and SA are passed to the core
• Core creates Group Traffic Encryption Key (GTEK) and

Group Key-encryption-keys (GKEK)

• Core distributes ACL, GTEK, GKEK to secondary routers.
• Internet Security Association and Key Management Protocol

(ISAKMP) is used to distribute keys between group members and the trusted routers. (guarantees the uniqueness of the session key between two entities.)

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Key Distribution Architectures

♦ Hierarchical Trees

– A hierarchical tree of key-encryption-keys is created. – Participants store all keys within the tree between themselves and the root – Efficient removal of participant – Scalable

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Key Distribution Architectures

♦ Secure Lock

– Use Chinese Remainder Theorem (CRT) to generate lock. – The lock is transmitted with each encrypted message. – Only users in the secure group can “unlock” the session key. – Flexible towards the dynamic addition and deletion of a group participant. – Not scalable for large group

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Key Distribution Architectures

♦ Distributed Registration and Key Distribution

(DiRK)

– A key distribution protocol designed for application

• ver MBONE.

– Active participant can help with registration and key distribution. – Hosts send registration request to request join session – Any active participant can respond. – Efficient due to the distributive nature – Highly scalable

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Key Distribution Architectures Comparison

♦ Manual Key Distribution— slow ♦ Pairwise Keying—linear efficiency for initial key

and rekey

♦ Hierarchical trees—linear efficiency for initial key

and logarithm rekey

♦ Secure Lock—linear efficiency for initial key and

constant rekey

♦ Distributed Registration and Key Distribution

(DiRK)—distributive linear efficiency for initial key and rekey (trust is a problem)

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Future Works

♦ Security application should be transparent

to users.

♦ Should work efficiently with other required

protocols.

♦ Focus on achieving a truly integrated

security solution that functions together with non-security functions and exisiting multicast protocols.