Group Key. Secrecy Before considering group key secrecy, we briefly examine key fresh- ness. Every group key is fresh, since at least one member in the group generates a new random key share for every membership change6. The probability that new group key is the same as any old group key is negligible due to bijectiveness of (f ◦ g) function. { } 6 Recall that insider attacks are not our concern. This excludes the case when an insider intentionally generates non-random numbers. We note that the root (group) key is never used directly for the purposes of encryption, au- thentication or integrity. Instead, special-purpose sub-keys are derived from the this key, e.g., by applying a cryptographically secure hash function, i.e. H(group key) is used for such applications. As discussed in Section 2.4, decisional group key secrecy is more meaningful if sub-keys are derived from a group key. Decisional group key secrecy of STR protocol is related to imbalanced tree decision Xxxxxx-Xxxxxxx assumption mentioned in Section A.2. This assumption ensures that there is no information leakage other than public bkey information. We can also derive sub-keys based on the Xxxxx’x hedge technique [25] and compute them as: H(group key) ⊕ H(group key) where H is a random oracle. It follows that, in addition to the security in the standard model based on the Imbalanced Tree Decision Xxxxxx-Xxxxxxx assumption, the derived key is also secure in the random oracle model [6] based on the Imbalanced Tree Computational Xxxxxx-Xxxxxxx assumption.
Group Key. It is a solitary key which is allotted just for one gathering of versatile hubs in MANET. For building up a gathering key, bunch key is making and circulating a mystery for bunch individuals. Secure choice of bunch heads is another noteworthy issue in MANETs. The general methodology in previous conventions is that every member freely reports the quantity of associations with different members. At that point, the one with the greatest number of association is chosen as a group head. Consequently, group head choice procedure is open for security dangers. For example, a noxious member can guarantee that it has the most elevated number of associations in its neighbourhood. At that point, the malignant member can control all the interchanges of the group.
