Post on 08-Apr-2018
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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
Hey 5
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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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