Network Security in Ring Multicast Diffie - Hellman Algorithm 1.A and B agree on a prime q and a number 1 <g <q. 2.A and B choose private keys, S A and S B. 3.A and B compute public keys, K A = g S A mod q K B = g S A mod q 4.For A, K = (K B ) S A mod p = g S A S B mod q For B, K = (K A ) S B mod p = g S A S B mod q X EA, D’EA, CD’EA da b c EABC * D’, CD’, BCD’, ABCD’ * * * e * E, D’E, CD’E, BCD’E EAB, D’EAB Member Addition Protocol a b c 2 AC’ 1 C’, BC’ * * * Member Exclusion Protocol e joins the multicast ring; d updates D to D’; New key will be ABCD’E. d leaves the multicast ring; c updates C to C’; New key will be ABC’. Mass Join Protocol ABF,ABEF, ABD’EF da b c * D’, CD’, BCD’, ABCD’ * * * e * f E,D’E, CD’E BCD’E, ABCD’E F,EF,D’EF, CD’EF BCD’EF, * AF,AEF, AD’EF, ACD’EF 4 ABCF, ABCEF 7 ABCD’F da b c 2 1 * D’’, CD’’, ACD’’ * * ef D’’F, CD’’F * 3 AD”F Subgroup Exclusion Protocol e, f join the group; Chain e & f in sequence; d updates D to D’; New key is ABCD’EF. b, e leave the group; d updates D to D’’; New key is ACD’’F. da b c ef a b c 2 AC’ 1 C’, BC’ * * * d ef Group 1: d e f 1 D’’ E’’, D’’E’’ F’’, E”F’’ * * * D’’F’’ Group 2: Subgroup Exclusion IKE Group Division Protocol Run the subgroup exclusion protocol to form Group 1; Run IKE to form Group 2. da b c Ko [F;0;new;B’,AB’,AB’D] * * * Ko [F;0;new;B’C,AB’C] Ko [F;0;new;B’CD] K N [G;1;-;-] Key Refresh with New word Policy Ko [F; 0; new; B’C,AB’C] Packet dataAlternating bitNew subkeys New key specified b refreshes the key; F & G are packet data; Key refresh doesn’t interrupt data flow. Key format KoKNKN Old key New key Key Refresh with Transformation K [F; 0; from d; T 1 ] Packet dataAlternating bitTransformation Refreshing member da b c * * * K [F;0;from d;T 1 ] * K [G;1;from d;T 1 ] T 1 K [G;1;-;-] K T1KT1K Key format d refreshes the key; F & G are packet data; New key is T 1 K; Key refresh doesn’t interrupt data flow. Key Refresh with Transformations K TK T=T A T B T C T D d a b c * * K [F;0;from d;T D ] K [G;1;from d; T D,T A ] K [G;1;from d; T D,T A,T B ] K [G;1;from d; T C,T A,T B ] K [G;1;from d; T B,T C ] * * K [H;0;from d;T C ] TK [H;0;-;-] d initiates the key refresh; Each member contributes its own transformation; F, G & H are packet data; Key refresh doesn’t interrupt data flow. Multicast Network Advantages: Low network transmission overheads High user scalability Applications: Stock quote services, Internet radio, Video conferencing, Pay per view TV Concerns: Backward/Forward secrecy Data confidentiality Membership changes (Dynamic Groups) Efficient key management scheme (Key Agreement, Key Refresh etc.) New word Policy in Ring Multicast N1N1 N1N1 M0M0 M0M0 M0M0 DC X 1 N1N1 N1N1 N1N1 N1N Station Station 1 is source; N 1 is new message; M 0 is prior packet; X means transmission error; DC means “Don’t Care”; 1 resent N 1 when seeing M 0. Secure Acknowledging Multicast (SAM) da b c 1 A B, AB C, BC, ABC * D, CD, BCD * * * AD,ACD ABD a is source; b, c, d are receivers; Group key is ABCD; Asterisk denotes receiver now has common secret key. ABCD AB ABC A Initial Key Establishment (IKE) Notations: SAM scheme achieves secure and efficient key agreement in the context of dynamic ring multicast network, such as initial key establishment, member addition, member exclusion, mass join, subgroup exclusion and group division etc. SAM provides both simple acknowledgement with new-word policy and simple key refresh via transformations. Key refresh does not interrupt the data exchange and acknowledgement. Conclusions Thank you for stopping by ! Any Questions ?? Contact us via John J. Metzner Yuexin Liu John J. Metzner, Yuexin Liu Dept. of Computer Science and Engineering, The Pennsylvania State University