Multicast encryption

Abstract: In this paper we introduce two notions of security: multi-user indistinguishability and multi-user non-malleability. We believe that they encompass the correct requirements for public key encryption schemes in the context of multicast communications. A precise and non-trivial analysis proves that they are equivalent to the former single-user notions, provided the number of participants is polynomial. We also introduce a new definition for non-malleability which is simpler than those currently in use. We believe that our results are of practical significance: especially they support the use of PKCS#1 v.2 based on OAEP in the multicast setting.

Abstract: We prove a computational soundness theorem for symmetric-key encryption protocols that can be used to analyze security against adaptively corrupting adversaries (that is, adversaries who corrupt protocol participants during protocol execution). Our soundness theorem shows that if the encryption scheme used in the protocol is semantically secure, and encryption cycles are absent, then security against adaptive corruptions is achievable via a reduction factor of O(n ċ (2n)l), with n and l being (respectively) the size and depth of the key graph generated during any protocol execution. Since, in most protocols of practical interest, the depth of key graphs (measured as the longest chain of ciphertexts of the form Ɛk1 (k2), Ɛk2 (k3), Ɛk3 (k4), ...) is much smaller than their size (the total number of keys), this gives us a powerful tool to argue about the adaptive security of such protocols, without resorting to non-standard techniques (like non-committing encryption). We apply our soundness theorem to the security analysis of multicast encryption protocols and show that a variant of the Logical Key Hierarchy (LKH) protocol is adaptively secure (its security being quasi-polynomially related to the security of the underlying encryption scheme).

Abstract: Multicast security is one of the most important security services in wireless sensor networks (WSNs) since it enables a sink to multicast messages to sensors in a secure manner. While multicast authentication has widely been addressed in the literature, the problem of multicast encryption still remains open in WSNs. In this paper, we propose a multicast encryption scheme called global-partition, local-diffusion (GPLD) that focuses on scheme efficiency and supports various multicast group semantics. GPLD partitions sensors into a series of elementary groups using their location and class information and accordingly builds a location-class-aware symmetric key management framework. Furthermore, the scheme leverages the fact that sensors are both end receivers and routers, which effectively minimizes global (sink-to-sensor) group key distribution and rekeying traffic while supporting various multicast group semantics. The efficiency and security properties of GPLD are justified through both analysis and simulations.

Abstract: Secure multicast provides efficient delivery which includes an identical data from a source to multiple receivers. A common solution is to apply a symmetric key that is used to encrypt the transmitted data. However, the heavy cost of the rekeying process is the main problem in large and dynamic multicast groups. The tree-based architecture is widely used to reduce the rekeying cost in terms of storage, transmission and computation. However, it usually requires extra overhead to keep key tree balance which is in order to achieve logarithmic rekeying cost. In this paper, we shall propose a new RSA-like multicast key management scheme to solve the rekeying problem. Our protocol applies a star-based architecture to eliminate the rekeying processes and provide the good performance when the membership changes in a multicast group. Furthermore, we also provide an extended multicast scheme, in which we combine public-key and symmetric-key cryptosystems to enhance the performance of multicast encryption.