1. Thor: The Hybrid Online Repository
Tim van der Horst and Kent Seamons
Internet Security Research Lab
Brigham Young University
Good afternoon.
Today, I am presenting Thor: The Hybrid Online Repository
First IEEE/CreateNet International Conference on Security and Privacy
for Emerging Areas in Communication Networks
Athens, Greece 5th-9th September 2005

2. Digital Repositories
Repository – a place to store and protect valuable objects
Digital credential repository stores and protects digital credentials
Important service to applications and protocols that use credentials
Many repositories have been created and successfully deployed
Not designed with the mobile environment in mind
What is a repository? –Give Def
Digital CRED repository – Give Def
This is a valuable support service for apps and protocols that use creds
Many digital repositories have been created and successfully deployed. However, many of these repositories were not designed with the mobile environment in mind.

3. Purpose Identify the requirements of a mobile environment
Evaluate existing repositories in light of these requirements
Present the design of a repository that meets these requirements
The purpose of this research is to…

4. Requirements Physical Security Connectivity Manageability
The loss of the mobile device must not equate to a loss of the user’s credentials
Connectivity
A user-defined subset of credentials must be accessible regardless of the current communications topology
Manageability
Provide an interface to manage and maintain credentials across all participating devices R1 R2
We have identified 3 requirements for secure credential repositories in a mobile environment
The first requirement has to do with physical security. Due to the small size of mobile devices and their use outside a trusted domain, they are more prone to loss, theft, and destruction. As such, our first requirement is that: --Give R1
The second requirement has to do with connectivity. Due to the transient nature of mobile devices, they can experience a variety of both connect and disconnected topologies. As such, our second requirement states: -- Give R2
Our third requirement has to do with manageability. Management, replication, and synchronization of credentials is a critical task. As such, our third requirement states: --Give R3 R3

5. Existing Repositories
Application
Local R1 R2 R3
Local
Repository
Now that we have a set of requirements to evaluate repositories in the context of a mobile environment, lets do so.
Existing repositories fall into two different types: Local and remote
Local – Existing entirely on-device, as such if the device is destroyed, so is the repository and its contents and thus does not satisfy our first requirement. Also, since the repository is contained completely on-device it doesn’t have the facilities to interact with the repositories on the user’s other participating devices.
Remote – resides completely off-device. Because of this, when the device is destroyed the credentials remain safe. This type of repository can be shared by all of a user’s participating devices, thus providing satisfaction for the third requirement.
Notice that the requirements satisfied by these two types of repositories are complimentary. That is to say, if we were to combine the correct elements of these repositories we should get I repository that does satisfy all of these requirements.
Application R1 R2 R3
Remote
The
Internet
Remote
Repository

6. Hybrid Repository R1 R2 R3 Application The Internet Remote Repository
Local
Repository
This is in fact what a hybrid repository does. It combines local and remote elements in order to satisfy all three requirements.

7. Thor A design for a hybrid repository Design Goals
Leverages existing repositories, rather than creating a new one
Design Goals
All three requirements for a secure credential repository in a mobile environment must be satisfied
There must be no modifications required to the existing repository implementations
Where possible, increase usability and security of existing repositories without modifying them G1 G2 G3

8. Thor – Repository Interface
Creates an additional layer of abstraction
All repositories have three basic operations:
Put
Get
Delete

9. Thor – Design Root repository constraints Must be a remote repository?
Leaf
Leaf
Leaf R2
  

10. Centralized Management
Provides a single location to manage credentials
Local agent
Stores and manages meta-data in the repositories
Contains additional information about the credentials
Used to manage credentials
Meta-data is stored as an encrypted credential in the repository R3

11. Thor – Enhancements Credential organization
Create a virtual organization
Credential identifier obfuscation
Password management
Create a mapping of secure passwords to credentials, encrypt with a single password
145c01342ee13a015954fefe01
Credit card credential
4fe4c30f4a2466f52a591071dd
CIA agent credential

12. Central Management
Transparent features

13. Evaluation Does Thor meet its goals?
All three requirements for a secure credential repository in a mobile environment must be satisfied
There must be no modifications required to the existing repository implementations
Where possible, increase usability and security of existing repositories without modifying them G1 G1 G2 G2 G3 G3

14. Conclusions
Delineated a set of requirements for a repository in a mobile environment
Evaluated existing repositories based on those requirements
Designed and implemented a hybrid repository
Satisfies requirements of a mobile environment
Leverages existing repositories
Provides transparent features that enhance the protection of its contents

15. Future Work Incorporate more repositories into this system
-based repository
No need for a specialized credential server
Context-aware application interface
Create a virtual smart card interface for each type of application
Usability