Authenticated GDH Sample Clauses

Authenticated GDH. One attempt to modify the GDH.2 protocol to provide implicit key authentication is to assume that one group key. As a result, m2 and mI share a key gyr3r2 that m2 believes to be the group key, and t hus the attack has succeeded and the IKA property is broken.

Authenticated GDH. 2 protocol l=0 l=1

Authenticated GDH. 2 (A-GDH.2) Round i (1 i n 1): Same steps from GDH.2 Round n: 1. Mn selects a random integer rn ∈ Zq∗. Fig. 1. Tree based representation of members. Each of them is given a two bit address 00, 01, 10, 11 re- spectively. Let the contribution by each member to a 2-party DH be SA, SB , SC and SD . In the first round, illustrated by 2. For each Mi, Mn sends Mi: {yi = αKi,n · 1≤j≤n,j=∗ i rj }. Figure 2(a), A and B engage a 2-party Xxxx-Xxxxxxx protocol 3. After receiving the above message, each M computes the and calculate the key SAB = αSASB ; C and D similarly calcu- group key as S r K−1 = i· . late the key SCD = αSC SD . In the next round, illustrated by n i Figure 2(b), A and C participate in the Xxxx-Xxxxxxx proto- In this protocol, each group member obtains an authenticated shared key with Mn. A slight modification of the A-GDH.2 is that Mn sends each member Mi the final key encrypted by some symmetric encryptions using key Ki,n instead of sending them some number and let Mi compute the key. In this variation, the member Mn basically acts as the trusted third party (TTP). col using SAB and SCD as random numbers instead of selecting new random numbers. In other words, they will generate a key αSAB SCD . Similarly, B and D also participate the Xxxx- Xxxxxxx protocol to get the key αSAB SCD . Thus, the final key calculated by all members is SABCD = αSAB SCD .

Authenticated GDH. 2 protocol

Authenticated GDH. One attempt to modify the GDH.2 protocol to provide implicit key authentication is to assume that one group member mn shares a secret Kin with each mi sepa- rately, and then modify the last message in GDH.2 so that the message parts are blinded using the keys shared with the recipients. The message that mn broadcasts r1···rn ·K key. As a result, m2 and mI share a key gyr3r2 that m2 believes to be the group key, and thus the attack has succeeded and the IKA property is broken.

Authenticated GDH. 2 protocol An extension of the GDH.2 protocol (Algorithm 1) to pro- l=0 l=1

Authenticated GDH. 2 (A-GDH.2) Round i (1 i n 1): Same steps from GDH.2 Round n: 1. Mn selects a random integer rn 2 Z .