Numero 36

fredag 22 november 1996, årgång 26

Veckoblad om forskning, undervisning och administration m.m.
NADA - Institutionen för numerisk analys och datalogi, KTH


Aktuellt kalendarium (inte kalendariet som hör specifikt till denna Numeroutgåva).

Måndagsseminarium: Examples of computations with unexpected results

Björn Sjögreen håller måndagsseminarium under ovanstående rubrik på måndag (25 nov.) kl. 15.15 i sal E2 (Osquars backe 2, plan 3).


We consider finite difference methods for solving partial differential equations. We can prove that the methods are convergent for certain simple model problems. However, for the realistic problems from, e.g., fluid mechanics, that we are solving, there are no mathematical proofs that the numerical methods converges. Does this have any importance in reality ? I will show examples of difficulties encountered in fluid dynamical computations, sometimes leading to non-convergence of methods known to be convergent when applied to simpler problems.

PDC-seminarium: The predictability problem

Erik Aurell håller PDC-seminarium under ovanstående rubrik fredagen den 29 nov. kl. 9.00 i seminarierum 1537 (Lindstedtsv. 3, plan 5).


This will be a report of work with the late Giovanni Paladin, and with Guido Boffetta, Andrea Crisanti and Angelo Vulpiani, published in Phys. Rev. Lett. vol 77 (1996), 1262 [short version].

PDC-seminarium: A linear in time algorithm for 2D gas dynamics without pressure

Andrei Sobolevsky håller PDC-seminarium under ovanstående rubrik på tisdag (26 nov.) kl. 15.15 i seminarierum 1537 (Lindstedtsv. 3, plan 5).

Erik Aurell

Postnummeruppslagning på Mac:ar

Nu finns postnummeruppslagning för Macanvändare i mappen Postinformation på NADA-arkiv. Starta programmet Postnummerkatalogen A-Ö i mappen Postnummerkatalogen.

Lasse C.

I korthet

Stipendier: Resebidrag ur Wallenbergsstiftelsens jubileumsfond. Numeropärmen 96.143

Stipendier: IVAs stipendier för vetenskapliga kontakter med republiken Korea. Numeropärmen 96.144

Stipendier: IVAs stipendier för vetenskapliga kontakter med Central- och Östeuropa. Numeropärmen 96.145

Pengar: Lista med anslag och stipendier från SU:s studentbyrå. Numeropärmen 96.146

Teoretisk datalogi-seminarium: Security Amplification for Two-party Protocols

Rafail Ostrovsky, Bellcore, håller seminarium i teoretisk datalogi under ovanstående rubrik torsdagen den 5 dec. kl. 15.15-16.15 i seminarierum 1537 (Lindstedtsv. 3, plan 5).


Abstract: A fundamental two-party completeness theorem, established by [Yao] and [Goldreich, Micali and Wigderson] shows that assuming the existence of one-way trapdoor permutations, two computationally bounded parties Alice (with private input $a$) and Bob (with private input $b$) can compute any polynomial-time two-argument function $f(a,b)$ with the following security guarantees: in the end of the protocol both parties will know $f(a,b)$ but such that for both parties any additional information about the other player input will be computationally hidden. In this talk, we show how to amplify the security for one of the two players in the above setting, and thus show a strictly stronger version of the above fundamental theorem. Namely, for one of the two parties, as before, any additional information (which does not follow from the output of the function) will be hidden computationally, while for the other player all the additional information will be hidden information-theoretically.

The implication is that a party (i.e., a citizen) may now be willing to undergo a "general function computation" against a potentially big brother (i.e. the government who possesses unknown computing power), since they can use the strong version where the security against that party is made independent of its computing power.

Joint work with Ramarathnam Venkatesan and Moti Yung

Johan Håstad

^ Upp till Numeros hemsida.

Senast ändrad 21 nov. 1996 <>