On the Complexity of the Tiden-Arnborg Algorithm for Unification modulo One-Sided Distributivity

We prove that the Tiden and Arnborg algorithm for equational unification modulo one-sided distributivity is not polynomial time bounded as previously thought. A set of counterexamples is developed that demonstrates that the algorithm goes through exponentially many steps.Comment: In Proceedings UNIF 2010, arXiv:1012.455

Unification modulo a 2-sorted Equational theory for Cipher-Decipher Block Chaining

We investigate unification problems related to the Cipher Block Chaining (CBC) mode of encryption. We first model chaining in terms of a simple, convergent, rewrite system over a signature with two disjoint sorts: list and element. By interpreting a particular symbol of this signature suitably, the rewrite system can model several practical situations of interest. An inference procedure is presented for deciding the unification problem modulo this rewrite system. The procedure is modular in the following sense: any given problem is handled by a system of `list-inferences', and the set of equations thus derived between the element-terms of the problem is then handed over to any (`black-box') procedure which is complete for solving these element-equations. An example of application of this unification procedure is given, as attack detection on a Needham-Schroeder like protocol, employing the CBC encryption mode based on the associative-commutative (AC) operator XOR. The 2-sorted convergent rewrite system is then extended into one that fully captures a block chaining encryption-decryption mode at an abstract level, using no AC-symbols; and unification modulo this extended system is also shown to be decidable.Comment: 26 page

On the equivalence problem for regular Thue systems

AbstractA decision procedure is presented for the equivalence problem for regular almost-confluent Thue systems. On the other hand, the equivalence problem for regular preperfect systems is shown to be undecidable

Evaluation Of National And Industry-Specific Interventions On Coir Industry In India A Special Reference To Kerala

The purpose of the study is to delineate the impact of national and industry-specific government interventions and the influence of political parties in power. The study employs an interrupted time series design from the annual national coir export data (1970-2012) published by the Coir Board. The study concludes by highlighting that the significance of economic environment has a greater impact on the trends of coir exports than industry-specific interventions. A seminal finding of this study is that there is a significant difference in the coir exports during the period of governance by the two political fronts in Kerala