Practical Memory Checkers for Stacks, Queues and Deques

. A memory checker for a data structure provides a method to check that the output of the data structure operations is consistent with the input even if the data is stored on some insecure medium. In [8] we present a general solution for all data structures that are based on insert(i; v) and delete(j) commands. In particular this includes stacks, queues, deques (double-ended queues) and lists. Here, we describe more time and space efficient solutions for stacks, queues and deques. Each algorithm takes only a single function evaluation of a pseudorandomlike function like DES or a collision-free hash function like MD5 or SHA for each push/pop resp. enqueue/dequeue command making our methods applicable to smart cards. 1 Introduction A memory checker guarantees that the data that is retrieved from memory is consistent with the data inserted before. Consider for example a stack and the sequence push(a), push(b), pop, push(a), push(c), pop, pop. Then the expected output is \Gamma, \Gamma, b..