Self-securing ad-hoc wireless networks (SSAWN)
Usually, an entity is trusted only if it is verified by a central authority, which cannot be the case in wireless and ad-hoc networks.
The goal of a self-securing network.
Achieve high-security assurance.
High success ratio.
Efficient communication.
Localized trust model, an entity is trusted if any k trusted entities claim so within a certain time period.
k entities typically among the entity’s one-hop neighbors.
Cares most about the trustworthiness of its immediate neighbors in practice - a node will communicate with the rest of the world via its one-hop neighbors.
Once a node is trusted by its local community, it is globally accepted as a trusted node.
Otherwise, a locally distrusted entity is regarded as untrustworthy in the entire network.
Shared secrets
The encryption mechanism uses RSA asymmetric keys.
Global Secret Key (SK) and the corresponding Public Key (PK).
SK functionality is 'distributed' among nodes.
Any K nodes holding a partial secret form a distributed Certificate Authority (CA).
SK is used to sign certificates for all nodes in the network.
A certificate signed by SK can be verified by the well-known public key P K.
Threshold secret sharing.
Each node has a part of the secret.
Unique ID, derived from the node's address.
The mechanism for local detection of misbehaving nodes.
At least K one-hop neighboring nodes.
Key pair for each node (public and secret keys).
Basic Operation
Basic operation.
Distributed PKI.
The system's private key is split into server nodes.
The quorum of k servers produces certificate updating.
Structure of certificate.
Operates in phases.
Server group formation/maintenance.
Certificate updating/revocation.
Shared key updating/renewing.
SK is not visible, known, or recoverable by any network node.
Each node carries a certificate signed with SK.
PK is assumed to be well-known for certificate verification.
Nodes without valid certificates are denied access to any network resources such as routing and packet forwarding.
Shared secrets
The partial secret key is a function of node IDs.
Generation of a polynomial of order K-1, known only in the initial setup.
K nodes holding a partial secret share recover SK using Lagrange interpolation.
A coalition of K-1 nodes holding a partial secret share does not have any information about SK.
Node wants to use the distributed CA.
Contact K nodes that have a partial secret share.
K one-hop neighboring nodes.
It is easier to collect reliable information about the misbehavior of closer nodes.
PK is known by all nodes
Upon the receipt of vi’s certification request, a node checks its records.
If its record shows vi as a well-behaving legitimate node, it returns a “partial” certificate by applying its share of SK.
Otherwise, the request is dropped.
By collecting k partial certificates, vi combines them together to generate the full new certificate as if it were from a CA server.
Upon receiving k partial certificates from the coalition, node vi multiplies them together to recover its full certificate (Lagrange interpolation – polynomial that passes through several points.
A misbehaving or broken node will be unable to renew its certificate.
A valid certificate represents the trust from a coalition of k nodes.
Nodes with valid certificates are globally trusted.
Each node contributes to the overall trust management and maintenance by monitoring and certifying its neighboring nodes.
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