Illinois
Security Lab
Rakesh Bobba , Omid Fatemieh, Fariba Khan, Carl A.
Gunter and Himanshu Khurana
University of Illinois at Urbana-Champaign

Illinois
Security Lab
Attribute-Based Messaging (ABM): Targeting messages based on attributes.
ACSAC 2006

Illinois
Security Lab
Attribute-Based Messaging (ABM): Targeting messages based on attributes.
Examples
• Address all faculty going on sabbatical next term
• Notify all female CS graduate students who passed qualifying exams of a scholarship opportunity
ACSAC 2006

Illinois
Security Lab
• Attribute-based systems have desirable properties
– flexibility, privacy and intuitiveness
• Attribute-Based Messaging (ABM) brings these advantages to e-mail messaging
– enhances confidentiality by supporting targeted messaging
• via dynamic and transient groups
– enhances relevance of messages
• by reducing unwanted messages
ACSAC 2006

Illinois
Security Lab
• Access Control
– access to such a system should be carefully controlled
• potential for spam
• privacy of attributes
• Deployability
– system should be compatible with existing infrastructure
• Efficiency
– system should have comparable performance to regular e-mail
ACSAC 2006

Ensuing Issues
•ABM Address
Format, Client I/F
•Access Control policy specification and enforcement
•Attribute Database creation and maintenance
Attr.
DB
ABM
Server
E-mail
MTA
Policy
Decision
Illinois
Security Lab
ACSAC 2006

Illinois
Security Lab
• Attribute database
– all enterprises have attribute data about their users
– data spread over multiple, possibly disparate databases
– assume that this attribute data is available to
ABM system
• “information fabric” , “data services layer”
• ABM address format
−logical expressions of attribute value pairs
−disjunctive normal form
ACSAC 2006

• Access Control Lists (ACLs)
– difficult to manage
Illinois
Security Lab
ACSAC 2006

Illinois
Security Lab
×Access Control Lists (ACLs)
× difficult to manage
• Role-Based Access Control (RBAC)
– simplified management if roles already exist
ACSAC 2006

× Access Control Lists (ACLs)
× difficult to manage
× Role-Based Access Control (RBAC)
× simplified management if roles already exist
• Attribute-Based Access Control (ABAC)
− uses same attributes used to target messages
− more flexible policies than with RBAC
• Access policy
− XACML is used to specify access policies
− Sun’s XACML engine is used for policy decision
ACSAC 2006
Illinois
Security Lab

• Problem
– need policy per logical expression
– policy explosion
• Solution?
– one policy per <attribute,value>
Illinois
Security Lab
ACSAC 2006

Illinois
Security Lab
• Use existing e-mail infrastructure (SMTP)
– address ABM messages to the ABM server (MUA) and add ABM address as a MIME attachment
• No modification to client
– use a web server to aid the sender in composing the
ABM address via a thin client (web browser)
• E-mail like semantics
– policy specialization
ACSAC 2006

AR1
AR2
Attribute
DB
MS SQL Server Policy xml
PDP
Sun’s XACML
Engine
PS2
PS7
Web Server
Windows IIS
ABM Server
Illinois
Security Lab
Sender
MS1
ACSAC 2006
MTA
Legend
PS: Policy
Specialization
MS: Messaging
AR: Address
Resolution

• Problem
– open to replay attacks
• Solution
– MTA configured with SMTP authentication
• with additional message specific checks
Illinois
Security Lab
ACSAC 2006

• Measured
– latency over regular e-mail
• with and without access control
– latency of Policy Specialization
• Setup
– up to 60K users
– 100 attributes in the system
• 20% of attributes common to most users
• 80% of attributes sparsely distributed
ACSAC 2006
Illinois
Security Lab

Illinois
Security Lab
ACSAC 2006

10
8
6
4
2
0
14
Policy Specialization Latency
12
143 282 398 568 674
Number of Policies
(Number of policies ~= 5 * Number of attributes)
ACSAC 2006
Illinois
Security Lab

Illinois
Security Lab
• Policy Administration
– one policy per <attribute ,value> not per address
– further be reduced to one policy per attribute
• Privacy
– of sender and receivers
– of ABM address
• Usability
– user interfaces
ACSAC 2006

Illinois
Security Lab
• Technologies
– List Servers
– Customer Relationship Management (CRM)
• Secure role-based messaging
• WSEmail
ACSAC 2006

Illinois
Security Lab
• Inter-domain ABM
– e.g., address doctors in the tri-state area who have expertise in a specific kind of surgical procedure
– challenge – “attribute mapping”
– application in ‘emergency communications’
• Encrypted ABM
ACSAC 2006

ACSAC 2006
Illinois
Security Lab