A distributed key establishment scheme for wireless mesh networks using identity-based cryptography

In this paper, we propose a secure and efficient key establishment scheme designed with respect to the unique requirements of Wireless Mesh Networks. Our security model is based on Identity-based key establishment scheme without the utilization of a trusted authority for private key operations. Rather, this task is performed by a collaboration of users; a threshold number of users come together in a coalition so that they generate the private key. We performed simulative performance evaluation in order to show the effect of both the network size and the threshold value. Results show a tradeoff between resiliency and efficiency: increasing the threshold value or the number of mesh nodes also increases the resiliency but negatively effects the efficiency. For threshold values smaller than 8 and for number of mesh nodes in between 40 and 100, at least 90% of the mesh nodes can compute their private keys within at most 70 seconds. On the other hand, at threshold value 8, an increase in the number of mesh nodes from 40 to 100 results in 25% increase in the rate of successful private key generations

Entangled cloud storage

Entangled cloud storage (Aspnes et al., ESORICS 2004) enables a set of clients to “entangle” their files into a single clew to be stored by a (potentially malicious) cloud provider. The entanglement makes it impossible to modify or delete significant part of the clew without affecting all files encoded in the clew. A clew keeps the files in it private but still lets each client recover his own data by interacting with the cloud provider; no cooperation from other clients is needed. At the same time, the cloud provider is discouraged from altering or overwriting any significant part of the clew as this will imply that none of the clients can recover their files. We put forward the first simulation-based security definition for entangled cloud storage, in the framework of universal composability (Canetti, 2001). We then construct a protocol satisfying our security definition, relying on an entangled encoding scheme based on privacy-preserving polynomial interpolation; entangled encodings were originally proposed by Aspnes et al. as useful tools for the purpose of data entanglement. As a contribution of independent interest we revisit the security notions for entangled encodings, putting forward stronger definitions than previous work (that for instance did not consider collusion between clients and the cloud provider). Protocols for entangled cloud storage find application in the cloud setting, where clients store their files on a remote server and need to be ensured that the cloud provider will not modify or delete their data illegitimately. Current solutions, e.g., based on Provable Data Possession and Proof of Retrievability, require the server to be challenged regularly to provide evidence that the clients’ files are stored at a given time. Entangled cloud storage provides an alternative approach where any single client operates implicitly on behalf of all others, i.e., as long as one client's files are intact, the entire remote database continues to be safe and unblemishe