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KAIS T Scalable Key Management for Secure Multicast Communication in the Mobile Environment Jiannong Cao, Lin Liao, Guojun Wang Pervasive and Mobile Computing 2 (2006) 2007. 11. 8 Kim Pyung
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Scalable Key Management for Secure Multicast Communication Introduction IP Multicast Saves a great deal of bandwidth Needs group key management in a scalable and secure manner Scalability Under the mobile Internet environment Frequent moving, joining and leaving, and the large size of a group 1-affects-N phenomenon ( re-keying message, # of enc/decryption ) Security Backward / forward confidentiality 2/15
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System Model and Assumptions Scalable and Hierarchical key management(SHKM) S : multicast source F: forwarding node, subgroup manager CA : Centralized authority Scalable Key Management for Secure Multicast Communication 3/15
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SHKM : Main idea Hierarchy by subgroup priority ordering F i » F j Initiation : RSA algorithm Randomly chosen TEKs by SGM The parameters for derivation of the lower group’s TEK from CA changing residue e j, related factor г ij Scalable Key Management for Secure Multicast Communication 4/15
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SHKM : Key Generation SGM S i chooses the TEK k i CA gets (PK, SK) by RSA PK : public key E PK (k i ) D SK (k i ) changing residue : e i = k i 2 mod n ( n is secret ) if S j » S i, related factor : г ji = h(Z k j e i mod P) k i Scalable Key Management for Secure Multicast Communication SiCA 5/15
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SHKM : Key Derivation TEK : k j requestsfor access S i parameters : e i, г ji E k j ( e i, г ji ) check S j » S i ? D k j ( e i, г ji ) TEK of S i : k i = h(Z k j e i mod P) г ji Scalable Key Management for Secure Multicast Communication SjCA 6/15
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SHKM : Key Modification the relationship : S j » S l » S i key modification : k l k l * e l * = ( k l *) 2 mod n г jl * = h(Z k j e l * mod P) k l * г li * = h(Z k l * e i mod P) k i Only direct successor and predecessor of S l Scalable Key Management for Secure Multicast Communication 7/15
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SHKM : Protocol analysis Adding a new subgroup A new subgroup S i into an existing multicast group the changing residue e i, related factor г (CA) No re-keying message and No re-generation of a new TEK for whole group Scalable vs Key Graph ? Backward confidentiality? S h » S i (new) » S j » S k » S l Scalable Key Management for Secure Multicast Communication 8/15
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SHKM : Protocol analysis Deletion of a subgroup For the higher-priority subgroups Delete the changing residue e, related factor г (CA) No re-key message For the lower-priority subgroups New TEK for lower-priority subgroups New changing residue e, related factor г (CA) vs Centralized protocols ? - the cost transferred to CA Scalable Key Management for Secure Multicast Communication 9/15
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SHKM : Protocol analysis Leaving of subgroup members Multiple leaving about h, (m i, m i+1, …, m i+h-1 ) in S l New TEK k l * for S l new changing residue e l (CA) For the higher-priority subgroups New related factor г (CA) For the lower-priority subgroups New TEK for lower-priority subgroups New changing residue e, related factor г (CA) Scalable Key Management for Secure Multicast Communication 10/15
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SHKM : Protocol analysis Joining of a new subgroup member New TEK k l * for S l new changing residue e l (CA) For the higher-priority subgroups New related factor г (CA) For the lower-priority subgroups backward confidentiality New related factor г (CA) Scalable Key Management for Secure Multicast Communication 11/15
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SHKM : Protocol analysis Migration of member between subgroups First entry delayed re-keying + periodic (FEDRP) A TEK timer table for members residing outside the subgroup Leaving or timer expire “Reset” A lower re-keying rate Scalable Key Management for Secure Multicast Communication 12/15
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Attack Analysis Continuous attack (in Lin’ scheme) k i is exposed S j » S i г ji = Z k j ID i mod P k i k i = Z k j ID i mod P г ji k i *= Z k j ID i mod P г ji * k i *=h( Z kj e i * mod P ) г ji * Sibling attack S j » S i and S j » S l h( Z kj e i * mod P ) = г ji * k i h( Z kj e l * mod P ) = г jl * k l Scalable Key Management for Secure Multicast Communication 13/15
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Evaluation n : # of group userss : # of groups t : # of ave successorsm : # of ave dir-successors r : related factor computatione : changing residue computation Scalable Key Management for Secure Multicast Communication 14/15
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Conclusions No re-keying messages, but some reporting messages Reduced enc/dec cost compared with decentralized transferred to CA The defense of malicious attacks Scalable Key Management for Secure Multicast Communication 15/15
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