A Protocol for Secure Instant Messaging in Tactical Networks

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A Protocol for Secure Instant Messagingin
Tactical Networks

• Jens Tölle
• Philipp Steinmetz
• Tobias Ginzler

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Overview

• Tactical instant messaging
• Requirements
• Groups
• Implementation
• Future work

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Tactical instant messaging

• Exchange of text messages
• Wireless network

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Tactical instant messaging

• Pros
• Low bandwidth consumption
• No misunderstandings through bad speech reception
• Easy asynchronous reading and logging
• Silent operation
• Cons
• Text input inconvenient for sender

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Requirements

• No single point of failure no servers
• Security
• Robust transmission
• Presence information
• Ease of use

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Server-based instant messenger features

• Central user directory
• Centralized communication
• Centralized security infrastructure
• Implicit user structure

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Server-based instant messenger features

• Central user directory
• Centralized communication
• Centralized security infrastructure
• Implicit user structure

Replaced by decentralized mechanisms!
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Security

• Confidentiality
• Integrity and authenticity
• Future work Non-repudiation

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Confidentiality

• Confidentiality by symmetric encryption
• Future work Integration of key-agreement protocol

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Integrity and authenticity

• Certificate infrastructure
• Required certificates on devices

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Integrity and authenticity

• Future work nodes provide own certificate if
  unknown
• Shared trusted certification authority (CA)

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Groups

• One group one communication channel
• Confidentiality by group wide symmetric
  encryption key
• Assignment strategies?

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Group communication

• Assign one multicast address per group
• All group members join their multicast group
• Multicast routing replaces application-side
  membership management

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Group assignment

• Single channel
• Choose from set of channels
• Invite to custom channel

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Group assignment
Assign multicast addresses

• Single channel 1 preset multicast address
• Choose from set of channels n preset multicast
  addresses
• Invite to custom channel multicast address
  derived from unique user id

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Group assignment
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Group interaction
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Group interaction

• No unwanted merge and split operations

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Implementation

• Java ME
• Runs on mobile devices
• Message signing sufficiently fast (1s on 400 MHz
  ARM)

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Future work

• Gateway to client/server-network
• Presence information in large networks

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Summary

• Secure text messaging
• No servers, wireless links
• Group-oriented communication
• User structuring required

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Thank you!Any questions?

• steinmetz_at_fgan.de