Secure commitment is a primitive enabling information hiding, which is one of the most basic tools in cryptography. Specifically, it is a two-party partial-information game between a "committer" and a "receiver", in which a secure envelope is first implemented and later opened. The committer has a bit in mind which he commits to by putting it in a "secure envelope". The receiver cannot guess what the value is until the opening stage and the committer can not change his mind once committed. In this paper, we investigate the feasibility of bit commitment when one of the participants (either committer or receiver) has an unfair computational advantage. That is, we consider commitment to a strong receiver with a To appear in Symposium on Theoretical Aspects of Computer Science (STACS) 92, February 13-15, Paris, France. y MIT Laboratory for Computer Science, 545 Technology Square, Cambridge MA 02139, USA. Supported by IBM Graduate Fellowship. Part of this work done while at IBM T.J. W...

Abstract Function approximation is essential to reinforcement learning, but the standard approach of approximating a value function and determining a policy from it has so far proven theoretically intractable. In this paper we explore an alternative approach in which the policy is explicitly

We use the assumption that all sets in NP (or other levels of the polynomial-time hierarchy) have efficient average-case algorithms to derive collapse consequences for MA, AM, and various subclasses of P/poly. As a further consequence we show for C 2 fP(PP);PSPACEg that C is not tractable

The notion of NP-completeness has provided a rigorous mathematical definition for measuring intractability of NP problems. But this measure applies only to worst-case complexity. Being NP-complete does not indicate that a problem is intractable on the average case. Indeed, some NP

the description of a new multiparty protocol devoted to the sharing of secrets whose main application is related to key management. The main particularity of this scheme is that it is based on a problem classified as DistNP-Complete under the average-case analysis, the so called Distributional Matrix

and minorization conditions to construct a formula giving an analytic upper bound on the distance to stationarity. A rigorous answer to (Q1) can be calculated using this formula. The desired characteristics of the target distribution are typically estimated using ergodic averages. Geometric ergodicity

We reviewed the results of arthrodesis of the first meta-tarsophalangeal joint and excisional arthroplasty of the lesser metatarsophalangeal joints performed on patients who presented intractable metatarsalgia and forefoot deformities. The study included 18 feet (15 patients) in 12 women and 3 men

Abstract Purpose To report the early results of suprachoroidal silicone implant surgery in intractable glaucoma. Materials and methods A modified silicone implant with no valve was implanted into the suprachoroidal space of 15 eyes with intractable glaucoma. Results The mean age of the patients

the successful treatment of six cases of postoperative intractable, Grade B pancreatic fistulae, in which fistula closure was achieved through the use of tissue adhesive. Methods Six subjects presented at our hospital with Grade B pancreatic fistulae after pancreaticoduodenectomy. In all cases, the drain amylase

ABSTRACT Being NP-complete has been widely interpreted as being computationally intractable. But NP-completeness is a worst-case concept. Some NP-complete problems are \easy on average", but some may not be. How is one to know whether an NP-complete problem is \di cult on average