139 lines
5.1 KiB
Markdown
139 lines
5.1 KiB
Markdown
# Delay Tolerant Networks Security
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#### Applications of DTNs
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##### Interplanetary communication
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<img src="img/o.png" alt="DTN in space" style="zoom:50%;" />
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> **Characteristics**
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>
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> - High intermittent connectivity
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> - Extremely long message travel time
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> - Delay: finite speed of light
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> - Low Transmission reliability
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> - Inaccurate position
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> - Limited visibility
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> - Low asymmetric Data Rate
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> **Security**
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> - CCSDS protocol
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> - space End to End security
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> - space end to end reliability
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##### Military
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> No consistent network infrastructure and frequent disruptions
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> **Characteristics**
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> - High intermittent connectivity
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> - Mobility, destruction, noise & attacks, interference
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> - Low transmission reliability
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> - positioning inaccuracy
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> - limited visibility
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> - Low data rate
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> **Security**
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> - Mainly MANET security
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> - Distribution of CAs (Certificate Authorities) in mobile ad hoc networks cannot provide military level security
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> - Combining a self-organised approach with an off-line trusted third-party
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##### Rural Areas
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> Providing internet connectivity to rural/developing areas
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> **Characteristics**
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> - Intermittent connectivity
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> - Mobility - sparse development
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> - High propagation delay
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> - Asymmetric data rate
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> 
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> **Security**
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> - Standard cryptographic techniques such as PKI and transparent encrypted file systems
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- Disaster-struck areas
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- Disconnected kiosks in rural areas
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- Remote sensing applications
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But also
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- Bulk data distribution in urban areas
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- Sharing of individual content in urban areas
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- Mobile location-aware sensing applications
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- Social mobile applications
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#### DTN Security Goals
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Due to the resource scarcity of DTNs, the focus is on protecting the DTN infrastructure from unauthorised access and use.
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- Prevent **access** by unauthorised applications.
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- Prevent unauthorised applications from asserting control over DTN infrastructure.
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- Prevent authorised applications from sending bundles at a rate or class of service for which they **don't have permission**.
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- Detect and discard bundles that were sent from unauthorised applications/users.
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- Detect and discard bundles whose headers have been modified.
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- Detect and discard compromised entities.
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Secondary emphasis is on providing optional end-to-end security services to bundle applications.
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#### DTN Security Challenges
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- High round-trip times and disconnections
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- Do not allow frequent distribution of a large number of certificates and encryption keys end-to-end.
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- More scalable to use users' keys and credentials at neighbouring or nearby nodes.
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- Delays or loss of connectivity to a key or certificate server
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- Multiple certificate authorities desirable but not sufficient and certificate revocation not appropriate
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- Long delays
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- Messages may be valid for days/weeks, so message expiration may not be able to be depended on to rid the network of unwanted messages as efficiently as in other types of networks.
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- Constrained Bandwidth
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- Need to minimise the cost of security in terms of network overhead (header bits).
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###### Traditional PKI not applicable
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- Traditional symmetric cryptography approaches are not suitable for DTNs for two major reasons
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- In PKI, a user authenticates another user's public key using a certificate
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- This is not possible without online access to the receiver's public key or certificates
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- PKIs implement key revocation based on frequently updated online certificate revocation lists
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- In the absence of instant online access to CAs' servers, a receiver cannot authenticate the sender's certificate.
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###### Identity Based Cryptography not applicable
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Identity-Based Cryptography (IBC) schemes, where the public key of each entity is replaced by its identity and associated public formatting policies, are not suitable for security in DTNs.
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- IBC does not solve the key management problem in DTNs
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- It is not scalable because it assumes that a user must know the public parameters for all the trusted parties.
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###### Mobile ad hoc Key Management Proposals not applicable
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- Virtual Certificate Authority
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- Not applicable due to the absence of trusted third parties
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- Certificate chaining based on pretty good privacy (PGP)
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- Not applicable due to insufficient density of certificate graphs
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- Peer-to-peer key management based on mobility
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- Not applicable due to certificate revocation mechanism
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#### Existing Mandatory DTN Security
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Based on the *bundle* protocol
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- Hop-by-hop bundle integrity
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- Hop-by-hop bundle sender authentication
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- Access Control (only legit users with right permissions)
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- Limited protection from DoS attacks
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- Payload Security Header is computed once at the source bundle agent, carried unchanged, and checked at the destination bundle agent (and possibly also security boundary bundle agents)
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- Bundle Authentication Header is computed at every sending bundle agent and checked at every receiving hop along the way from the source to the destination.
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Current DTN security initiative is based on pre-shared secrets and involves no trust dynamics mechanisms
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- Works well against external threats but not applicable to internal threats
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