[HGI-News-de] HGI Seminar am MONTAG, den 15. Sept: "Group Key Exchange with Extern. and Int. Session Id. Generation" von Jun FURUKAWA

[Newsletter des Horst Görtz Instituts]

Halllo,

im Rahmen des HGI-Seminars "Aktuelle Themen der IT-Sicherheit" wird  
am Montag, den 15. September der folgende Vortrag angeboten:

Furukawa Jun (NEC Japan)
"Group Key Exchanges with Internal and External Session Identity Generation and Their Lower Bounds on Communication Complexity"

Termin:
Montag, der 15. September um  11.00 Uhr
Raum: IC 4/161.

Alle Interessierte sind herzlich eingeladen!


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Zusammenfassung:

A group key exchange (GKE) protocol allows n parties to establish a common group key in an insecure network. To prevent insider attacks as well as outsider attacks, Katz and Shin considered a universally composable (UC) security notion and showed a three round UC GKE protocol that requires 3(n2-n) messages to be exchanged in it.  This UC notionof GKE assumes that each protocol run is given a globally unique session identity (SID) by an external algorithm. 
On the other hand, AKE- and MA-security introduced by Bresson et al. assumes no such identities and these SIDs are determined within the protocols.  We considered here the both types of GKEs, that are GKE with internal SID generation and that with external SID generation.  We first prove these GKEs require at least 2 rounds of communication to prevent insider attacks. Next, we derive lower bounds on the number of messages to be exchanged in 2-round GKEs. They are 2n(n-1) messages when SIDs are internally generated and (1/2)n2 +O(n) messages when SIDs are externally generated.  Finally, we shows these lower bounds are in fact the minimums by showing concrete examples.

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Gruß,
Biljana Cubaleska