TRS-80 With A Keccak Sponge Cake

The subject of this paper, an improbable implementation of a recently standardized cryptographic hash function on a thirty-five-year-old microcomputer, may strike some as unusual and recreative at best. In the tedious discipline of the process, however, lessons were learned in implementation trade-offs for basic cryptographic primitives which may prove interesting in the current context of securing (small to nano) machine to machine communications. More importantly, that such insights might stem out of revisiting how earlier computing platforms relate to the code written on them to cast a distant light on modern connections of code to material, historical and contextual factors certainly illuminates the joys of retrocomputing

Gimli, Lord of the Glittering TRS-80

Bernstein et al. have proposed a new permutation, Gimli, which aims to provide simple and performant implementations on a wide variety of platforms ranging from the AVR ATmega and ARM-Cortex to the Intel Haswell. In a festive spirit of retrocomputing, this brief paper reports such a simple and (somewhat) performant implementation on the almost Third-Age-of-Middle-earth-dating TRS-80

The PERT Problem with Alternatives: Modelisation and Optimisation

Management of projects often requires decisions concerning the choice of alternative activities. The completion time of the whole project (i.e. the makerpan) is computed subsequently. In this paper, we aim at selecting the activities and computing the makespan simultaneously. This problem is referred to as PERT Problem with Alternatives (PPA). The corresponding model is similar to a conventional PERT graph, except that two types of nodes are introduced to represent either the choice between activities, or the fact that a set of activities should be completed before starting a subsequent set of activities. In this paper, we analyse the PPA and we propose a pseudo-polynomial algorithm to solve it

Scheduling and Controlling Work-in-Process : An on Line Study for Shop Problems

In this paper, we address the problem of production systems having two characteristics. First, the manufacturing times can be chosen between given bounds. Such a production system is said to have controllable processing times. Second, an operation must start as soon as the previous operation on the same part (if any) is completed. A production system having this characteristic is said to be no-wait. Several on-line schedules are considered to minimize the makespan in flow shop and job shop situations. We prove that in the worst case, the makespan provided by these schedules is m times longer than the optimal one (for different flow shops and job shops), m being the number of machines. We give several related results on competitive ratio

On-line Scheduling in Assembly Processes

The assembly system under consideration is composed with several machines, and some of these machines may be identical or able to perform the same operations. The manufacturing system is fully automated and, semi-finished products or components are not stored during the process. A limited flexibility exist since the manufacturing times can be extended within certain limits at the expense of the unavailability of the resource. There are no conflicts between the resources; in other words, the same machine cannot be used to perform different operations for a same product. Due to the intensity of the flow of products to be manufactured. It is not allowed to reschedule products which have been previously scheduled. Thus, when a new product requirement arrives in the system, we have to take advantage of the idle time windows. The goal is to complete the product as soon as possible. We give a real-time scheduling algorithm which guarantees an optimal makespan to any product which arrives in the assembly system. A numerical example is provided to illustrate this approach