alx seminar

8/6/2019 ALX Seminar

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CCEGK Group Key Protocol andits comparison

TE SeminarAlex James

Roll no. 3205

Guide: Prof. H.S. Narvekar

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Cryptography

Cryptography is the practice and study of the art of hidinginformation.

Cryptography has been used (as early as 1900BC) for thousands of years to avoid theinterception of confidential communications.

W ith the increased dependence of the current generation oncomputers, the need to ensure secure communications hastaken top priority. The science has undergone radical changeto meet these newer expectations.

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Diffie-Hellm an K ey Exchang e

Alice Bob

37 m od 17 = 11 310 m od 17 = 8

7m od 17 = 15

10m od 17 = 15

Pr ime: N = 17Int e ge r: G = 3

a = 7 b = 10

811

15Se cre t Key

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Encrypt ion us ing th e shar e d k ey

Alice Bob

15Se cre t ey

01001000 01101001 00100001

H i !

Hi!

00001111 00001111 0000111101000111 01100000 00101110

00001111 00001111 00001111

01001000 01101001 00100001

Hi! 4


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Encrypt ion us ing th e shar e d k ey

Alice Bob

15Se cre t ey

01001000 01100101 01111001

H e y

Hey

00001111 00001111 0000111101000111 01101010 01110110

00001111 00001111 00001111

01001000 01100101 01111001

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But what about s e cur e

co mm un icat ion in a group?

D iffie-Hellman key exchange thus effectively addresses secure

two -party communication

Can w e ext e nd th is conc e pt to m u lt ip le hosts?

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TheComm un icat ion -Com putat ion E fficie ntGroup K ey protoco l

(CCEGK)

An Ele gant So lut ion

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T he CCEGK Protoco l

This protocol was introduced in 200 7 by ShanyuZheng, D avid Manz, Jim Alves-Foss of the Universityof Idaho

Based on previous contributory keymanagement protocols such as the EGK andthe TG D H algorithms

Addresses issues regarding both communication and computation

costs

Considerably improves the computation and communication costs of the operations of the preceding group key management protocols

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O pe rat ions in CCEGK

The CCEGK composes of various operations:

INITIALISATION initial creation of the key managementinfrastructure

MASS JOIN adding multiple members to the group

JOIN adding a new member to the group

MERGE fusing two groups together

LEAVE a single member leaves the group

MASS LEAVE multiple members leave the group

PARTITION a single group is divided into two ormore groups

KEY REFRESH constantly updating the key9


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Ce rta in Assu m pt ions

The CCEGK utilizes a binary tree structure

The following assumptions are consistent throughoutgroup-key literature:

All members know the key structure, an ordered listof each other s identities, and their initial positionin the tree

All participants can unambiguously determine their groupsponsor

Every member sees the same sequence of group operations

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Notat ions

Host

Broadcast

Tree structur e nod e

Un icast11


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Bas ic Work ing

H1 H2

Se cre t key : 8

Prime : 23Integer : 5

Se cre t key : 9

Blind e d Key: Blind e d Key: 58 m od 23 = 16 59 m od 23 = 11

11 8 m od 23 = 8 16 9 m od 23 = 8

Se cre t Key : 8Blind e d Key : 58 m od 23 = 16

Diffie-Hellm an Key Pa ir : ( 8, 16 )

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Init ia lizat ion

(s1,b 1) (s2,b 2)

(S,B)

Group G

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Jo in

(S,B)

Group G

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M e rge

(s1,b 1) (s2,b 2)

(S,B)

Group G

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M ass Jo in

There are three kinds of mass-join operation in theCCEGK:

M ass jo in -ite rat ive

M ass jo in -me rge

Treats N members as N separate member joins

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Initialize the N different members into their ownindependent group and then merge the new group with theoriginal


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M ass Jo in

There are three kinds of mass-join operation in theCCEGK:

Treats N members as N separate member joins

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M ass jo in -sim u ltan e ous


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M ass Jo in -Sim u ltan e ous

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Le ave

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M ass Le ave

There are two kinds of mass-leave operations in theCCEGK:

M ass Le ave - ba lanc e d

M ass Le ave - im ba lanc e d

Initialize the whole group, leaving out theN leaving members

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Sponsors for each leaving node update their keys up the keypath and exchange blinded keys until the entire structure isupdated.


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M ass Le ave - Im ba lanc e d

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Part it ion

There are two kinds of mass-leave operations in theCCEGK:

Part it ion - ba lanc e d

Part it ion - im ba lanc e d

Initialize both the group separately fromthe beginning

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Use mass-leave imbalanced operation and then performinitialization operation on the leaving members


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Key Ref re sh

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The key is refreshed periodically to reduce thechances of outside intrusion.

The group s sponsor picks a new secret key andcalculates the blinded keys and secret keys upto theroot of the tree.

The sponsor then broadcasts it to all the members

who then calculate the keys individually.


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W orld W ide W eb and the Internet

Conference calls and Video Conferencing

D istributed System

Multiplayer Games

W hiteboard and D istributed D atabases

Applications of CCEGK

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CCEGK offers an elegant solution to the problem of securegroup key communication.

It possesses the best characteristics of the other group keymanagement protocols, addressing performance and security.

It is considerably more efficient than algorithms that came

before it in terms of both computation and communication.

Conclusion

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TH ANK YOU

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