On the Circuit Complexity of Perfect Hashing
نویسندگان
چکیده
We consider the size of circuits that perfectly hash an arbitrary subset S⊂{0, 1} of cardinality 2 into {0, 1}. We observe that, in general, the size of such circuits is exponential in 2k−m, and provide a matching upper bound.
منابع مشابه
Perfect Hashing, Graph Entropy, and Circuit Complexity
We present two simple and general techniques, both of which should find further application. First, we show that approximate compaction can be efficiently performed in constant parallel time using perfect hash functions. This allows us to show that polylogarithmic-threshold functions are in linear $AC^0$. Next, we show that the information theoretic notion of graph entropy captures some aspect ...
متن کاملUsing Tries to Eliminate Pattern Collisions in Perfect Hashing
4any current perfect hashing algorithms suffer from the problem of pattern collisions. In this paper, a perfect hashing technique that uses array-based tries and a simple sparse matrix packing algorithm is introduced. This technique eliminates all pattern collisions, and because of this it can be used to form ordered minimal perfect hash functions on extremely large word lists. This algorithm i...
متن کاملDynamic Perfect Hashing: Upper and Lower Bounds
The dynamic dictionary problem is considered: provide an algorithm for storing a dynamic set, allowing the operations insert, delete, and lookup. A dynamic perfect hashing strategy is given: a randomized algorithm for the dynamic dictionary problem that takes O(1) worst-case time for lookups and O(1) amortized expected time for insertions and deletions; it uses space proportional to the size of...
متن کاملA Practical Minimal Perfect Hashing Method
We propose a novel algorithm based on random graphs to construct minimal perfect hash functions h. For a set of n keys, our algorithm outputs h in expected time O(n). The evaluation of h(x) requires two memory accesses for any key x and the description of h takes up 1.15n words. This improves the space requirement to 55% of a previous minimal perfect hashing scheme due to Czech, Havas and Majew...
متن کاملOn the computational complexity of finding a minimal basis for the guess and determine attack
Guess-and-determine attack is one of the general attacks on stream ciphers. It is a common cryptanalysis tool for evaluating security of stream ciphers. The effectiveness of this attack is based on the number of unknown bits which will be guessed by the attacker to break the cryptosystem. In this work, we present a relation between the minimum numbers of the guessed bits and uniquely restricted...
متن کامل