Distributing a Private Key Generator in Ad hoc Networks: Authority Distribution Using Threshold Cryptography

The nodes in a Mobile Ad hoc Network (MANET) have limited computing and bandwidth resources, making the design of methods for cryptographic key management particularly challenging. Because the network infrastructure is unstable, assuming that authorities used in key management are implemented using any single node is unrealistic. Threshold cryptography can be used to distribute an authority, such that it is implemented by multiple nodes. This makes the authority more robust against network failures and harder to compromise. Identity-based cryptography (IBC), where any identity may serve as a public key, makes certificates and certificate distribution superfluous. The authority issuing private keys corresponding to identities is called a Private Key Generator (PKG). This thesis considers distributing a PKG to the nodes in a MANET. It gives a description of a generic distributed PKG, including a definition of security. An example of a distributed PKG is also given. This distributed PKG is compatible with some of the most prevalent IBC systems. It is shown that the security properties of the base IBC systems are preserved when this distributed PKG is used instead of the original.