a methodology for analyzing the performance of authentication protocols

Analyzing the Performance of Authentication Protocols

1

A Methodology for Analyzing the performance of Authentication

ProtocolsAlan HarbitterDaniel A. Menasce

Presented byRob Elkind


2

Outline• Introduction• Kerberos – and extensions• Kerberos with Proxy• Methodology • Simulations – Multiple Realm and Mobile

with proxy• Conclusion


3

Introduction

• Use of new modeling methodology for analyzing authentication protocols – Closed queuing network model

• Two Kerberos examples will be tested• Designed to explicitly model performance

new protocol design including asymmetric and symmetric encryption


4

Kerberos Overview


5

Kerberos Realms• Kerberos realms - networked collection of workstations,

servers, and a single master KDC which must: • 1. maintain a database of matching user IDs and hashed

passwords for registered Kerberos users• 2. maintain shared secret keys with each registered

application server• 3. maintain shared secret keys with remote KDCs in other

realms• 4. propagate new or changed secret keys and database

updates to slave KDCs.


6

Public Key Cryptography

• Increase scalability• Smaller key shared space ~ n2 vs. n for n

users• Improved Security• Proposals:

– PKINIT (core specification)– PKCROSS– PKTAPP


7

PKINIT Overview


8

PKCROSS Overview


9

PKDA Overview (PKTAPP)


10

Proxy server with Kerberos

• Isolate client and server for security purposes

• Offload processing from mobile host or network

• IAKERB• Charon


11

Methodology

• Build model• Validate• Change parameters• Analyze results• Add “What ifs”


12

Modeling Topology multiple-realm


13

Validation of Model


14

“What-If” Analyses

• Vary input parameters to reflect various real world conditions

• Reflects sensitivity to various operational environments

• Gives insight into general performance characteristics of the protocol design


15

Analysis of Public-Key-Enabled Kerberos in Large Networks

• Compare PKTAPP and PKCROSS• Simulate using closed queuing network

model• Use skeleton software to model real world

protocol• When is it more efficient to authenticate to

a central KDC than to individual application servers?


16


17


18

PKCROSS vs. PKTAPP


19

“What-Ifs” Results


20

Analysis Of Public-key-enabled Kerberos InMobile Computing Environments

• Reduce the number of public/private key operations performed on the mobile platform.

• When a proxy is used, maintain the option to preserve the encrypted data stream through the proxy.

• Retain the standard Kerberos formats for messages sent to the KDC and application server.

• Preserve the semantics of Kerberos.


21

M-PKINIT


22

MP-PKINIT


23

Modeling Topology M&MP-PKINIT

• Can use same model as before – Substitute a mobile client for client– Wireless network for LAN– Proxy server for local KDC

• Adjust branching probabilities to reflect new model paths


24

Model Results


25

Model vs. Simulation


26

“What-If” Analysis


27

More “What-Ifs”


28

Conclusions

• Closed queuing model with class switching is a useful tool for analyzing performance in security protocols – supports wide range of operating conditions

• Skeleton implementation is a good way to work with new ideas that may not be operational yet

• PKCROSS outperforms PKTAPP for authenticating to more than one server

• Proxy server benefits 2G speeds but not 3G speeds


29

Thoughts

• Well written and presented, clear and detailed

• Good procedural methodology• Would be nice to see “What-Ifs” done on

the test bed and compared to model as well• Skeleton makes assumptions that may alter

results when performed with real implementation


30

Questions?

a methodology for analyzing the performance of authentication protocols

Documents