EFFICIENT AND SCALABLE NETWORK SECURITY PROTOCOLS BASED ON LFSR SEQUENCES

The gap between abstract, mathematics-oriented research in cryptography and the engineering approach of designing practical, network security protocols is widening. Network researchers experiment with well-known cryptographic protocols suitable for different network models. On the other hand, researchers inclined toward theory often design cryptographic schemes without considering the practical network constraints. The goal of this dissertation is to address problems in these two challenging areas: building bridges between practical network security protocols and theoretical cryptography. This dissertation presents techniques for building performance sensitive security protocols, using primitives from linear feedback register sequences (LFSR) sequences, for a variety of challenging networking applications. The significant contributions of this thesis are: 1. A common problem faced by large-scale multicast applications, like real-time news feeds, is collecting authenticated feedback from the intended recipients. We design an efficient, scalable, and fault-tolerant technique for combining multiple signed acknowledgments into a single compact one and observe that most signatures (based on the discrete logarithm problem) used in previous protocols do not result in a scalable solution to the problem. 2. We propose a technique to authenticate on-demand source routing protocols in resource-constrained wireless mobile ad-hoc networks. We develop a single-round multisignature that requires no prior cooperation among nodes to construct the multisignature and supports authentication of cached routes. 3. We propose an efficient and scalable aggregate signature, tailored for applications like building efficient certificate chains, authenticating distributed and adaptive content management systems and securing path-vector routing protocols. 4. We observe that blind signatures could form critical building blocks of privacypreserving accountability systems, where an authority needs to vouch for the legitimacy of a message but the ownership of the message should be kept secret from the authority. We propose an efficient blind signature that can serve as a protocol building block for performance sensitive, accountability systems. All special forms digital signatures—aggregate, multi-, and blind signatures—proposed in this dissertation are the first to be constructed using LFSR sequences. Our detailed cost analysis shows that for a desired level of security, the proposed signatures outperformed existing protocols in computation cost, number of communication rounds and storage overhead

CONSTRUCTION OF EFFICIENT AUTHENTICATION SCHEMES USING TRAPDOOR HASH FUNCTIONS

In large-scale distributed systems, where adversarial attacks can have widespread impact, authentication provides protection from threats involving impersonation of entities and tampering of data. Practical solutions to authentication problems in distributed systems must meet specific constraints of the target system, and provide a reasonable balance between security and cost. The goal of this dissertation is to address the problem of building practical and efficient authentication mechanisms to secure distributed applications. This dissertation presents techniques to construct efficient digital signature schemes using trapdoor hash functions for various distributed applications. Trapdoor hash functions are collision-resistant hash functions associated with a secret trapdoor key that allows the key-holder to find collisions between hashes of different messages. The main contributions of this dissertation are as follows: 1. A common problem with conventional trapdoor hash functions is that revealing a collision producing message pair allows an entity to compute additional collisions without knowledge of the trapdoor key. To overcome this problem, we design an efficient trapdoor hash function that prevents all entities except the trapdoor key-holder from computing collisions regardless of whether collision producing message pairs are revealed by the key-holder. 2. We design a technique to construct efficient proxy signatures using trapdoor hash functions to authenticate and authorize agents acting on behalf of users in agent-based computing systems. Our technique provides agent authentication, assurance of agreement between delegator and agent, security without relying on secure communication channels and control over an agent’s capabilities. 3. We develop a trapdoor hash-based signature amortization technique for authenticating real-time, delay-sensitive streams. Our technique provides independent verifiability of blocks comprising a stream, minimizes sender-side and receiver-side delays, minimizes communication overhead, and avoids transmission of redundant information. 4. We demonstrate the practical efficacy of our trapdoor hash-based techniques for signature amortization and proxy signature construction by presenting discrete log-based instantiations of the generic techniques that are efficient to compute, and produce short signatures. Our detailed performance analyses demonstrate that the proposed schemes outperform existing schemes in computation cost and signature size. We also present proofs for security of the proposed discrete-log based instantiations against forgery attacks under the discrete-log assumption

Towards secure end-to-end data aggregation in AMI through delayed-integrity-verification

The integrity and authenticity of the energy usage data in Advanced Metering Infrastructure (AMI) is crucial to ensure the correct energy load to facilitate generation, distribution and customer billing. Any malicious tampering to the data must be detected immediately. This paper introduces secure end-to-end data aggregation for AMI, a security protocol that allows the concentrators to securely aggregate the data collected from the smart meters, while enabling the utility back-end that receives the aggregated data to verify the integrity and data originality. Compromise of concentrators can be detected. The aggregated data is protected using Chameleon Signatures and then forwarded to the utility back-end for verification, accounting, and analysis. Using the Trapdoor Chameleon Hash Function, the smart meters can periodically send an evidence to the utility back-end, by computing an alternative message and a random value (m', r) such that m' consists of all previous energy usage measurements of the smart meter in a specified period of time. By verifying that the Chameleon Hash Value of (m', r) and that the energy usage matches those aggregated by the concentrators, the utility back-end is convinced of the integrity and authenticity of the data from the smart meters. Any data anomaly between smart meters and concentrators can be detected, thus indicating potential compromise of concentrators

Sequential message authentication code without random oracles

Katz et al. provided a generic transform to construct aggregate message authentication codes and imposed a lower bound on the length of one aggregate MAC tag. The lower bound shows that the required tag length is at least linear with the number of messages when fast verification such as constant or logarithmic computation overhead is required. Aggregate message authentication codes are useful in settings such as mobile ad-hoc networks where devices are resource-constrained and energy cost is at a premium. In this paper, we introduce the notion of sequential aggregate message authentication code (SAMAC). We present a security model for this notion under unforgeability against chosen message and verification query attack and construct an efficient SAMAC scheme by extending a number-theoretic MAC construction due to Dodis et al. We prove the security of our SAMAC scheme under the CDH assumption in the standard model. Our SAMAC scheme improves the lower bound with the help of the underlying algebraic structure. Performance analysis shows that our SAMAC scheme yields constant computation for the verifier as well as fixed length for one aggregate

Verifiably encrypted cascade-instantiable blank signatures to secure progressive decision management

National Research Foundation (NRF) Singapore under NC

Unifying Static And Runtime Analysis In Declarative Distributed Systems

Today’s distributed systems are becoming increasingly complex, due to the ever-growing number of network devices and their variety. The complexity makes it hard for system administrators to correctly configure distributed systems. This motivates the need for effective analytic tools that can help ensure correctness of distributed systems. One challenge in ensuring correctness is that there does not exist one solution that works for all properties. One type of properties, such as security properties, are so critical that they demand pre-deployment verification (i.e., static analysis) which, though time-consuming, explores the whole execution space. However, due to the potential problem of state explosion, static verification of all properties is not practical, and not necessary. Violation of non-critical properties, such as correct routing with shortest paths, is tolerable during execution and can be diagnosed after errors occur (i.e., runtime analysis), a more light-weight approach compared to verification. This dissertation presents STRANDS, a declarative framework that enables users to perform both pre-deployment verification and post-deployment diagnostics on top of declarative specification of distributed systems. STRANDS uses Network Datalog (NDlog), a distributed variant of Datalog query language, to specify network protocols and services. STRANDS has two components: a system verifier and a system debugger. The verifier allows the user to rigorously prove safety properties of network protocols and services, using either the program logic or symbolic execution we develop for NDlog programs. The debugger, on the other hand, facilitates diagnosis of system errors by allowing for querying of the structured history of network execution (i.e., network provenance) that is maintained in a storage-efficient manner. We show the effectiveness of STRANDS by evaluating both the verifier and the debugger. Using the verifier, we prove path authenticity of secure routing protocols, and verify a number of safety properties in software-defined networking (SDN). Also, we demonstrate that our provenance maintenance algorithm achieves significant storage reduction, while incurring negligible network overhead