Key Distribution Scheme in Home-Network Security on Power Line Communication

Transcription

1 Key Distribution Scheme in Home-Network Security on Power Line Communication ETRI - ISIT Joint seminar Ryuzou Nishi ( ISIT )

2 2 Contents Introduction Home-Network Security Trends of High Speed PLC(Power Line Communication) Security of PLC Home-Network Security about Information Machinery and AV System Security about Control System Security about Community Communication Comparison between the Power Line and Wireless Conclusion Group Rekey Distribution

3 Introduction The Internet's popularization A huge variety of household appliances is expected to connect the Internet Entertainment Home network CE Transmission media LAN cable low speed power line Wireless e.g.ieee security equipment Telecommunication IT device newly High speed power line 3

4 Home-Network Security new risks Conventional risks mainly, leakages of personal information e.g. bank account New risks The safety of the human being and a life is exposed to the danger. The possibility of the leakage of the new personal information such as the use amount of electric power and the attention tendency of the television Electroricity Crime prevention equipment is switched off. A power supply is stopped An attacker can execute these, hiding his identity from the place which left the home far. Gas The gas supply is stopped A bath is prepared selfishly 4

5 Home-Network Security countermeasure Countermeasures according to the model Gateway model GW structure process Gateway has all security function points Each node's resource is least If GW is broken, The damage is biggest. distribution board PLC modem PLC modem power line Hierarchical model Individual model GW GW GW * Hierarchized gateway model * different cipher key is used in each layer Every node has a security function individually If some layer's GW is broken, The damage to the other layer is small. flexible Big CPU power is requested at each node Key management is complex distribution board In the environment of PLC, possible measure model is only the individual model 5

6 Trends of High Speed PLC The trend of every country USA 2000 for Home-Network Industry Alliance "HomePlug Power Alliance" was formed 2001 HomePlug v1.0 14Mbps specification release 2005 HomePlug AV about 200Mbps specification is being created EU The commercial services of access network began in Spain and Germany and so on. Japan 2003 PLC-J High Speed Power Line Communication Promoters' Alliance of Japan was formed 2004 High Speed PLC's experiment was permitted 6

7 Trends of High Speed PLC The technical characteristics The main reason that it was possible to communicate at high speed The advance of the communication technology Multi-carrier OFDM Orthogonal Frequency Division Multiplexing) improves the tolerance of noise and multipass The adoption of the modulation of the high spectral efficiency The expansion of frequency band width frequency the use of the more broadband ( 2M~30MHz ) In Japan, at present, it isn't possible to use this band and it needs a deregulation. 7

8 Trends of High Speed PLC The Example of developed PLC modem HomePlug AV specification Freq. band 2MHz 30MHz Max.data rate about 200Mbps PHY Specification of the prototype module modulation Wavelet OFDM sub-carrier 2PAM to 16PAM band-width 4 to 28MHz Max.data rate 190MHz Output level less than 50 dbm/hz power line FTTH PC Media server TV TV 8

9 Security of PLC Home-Network The main characteristics Signal attenuation level of distribution board is small The unwanted radiation The security measure using GW is difficult tapping is easy It peels off the film the cable and it connects. and it eavesdrops The electric outlet is in the everywhere of indoor or out of door. FTTH Power line Distribution Board modem PLC modem Gateway LAN cabel Distribution Board information leakage through power line Printer PC Power line information leakage through unwanted radio 9

10 The security about the Information machinery and AV system Security Issues The security using the gateway is difficult. information leakage through power line distribution board PLC modem information leakage through unwanted radio FTTH power line modem gateway LAN cable PC power line information leakage through power line information leakage through leak radio 10

11 The security about the Information machinery and AV system Expected risks The always-on connection risk The risk is bigger than the conventional wired type. The illegal access which used an outdoor power electric outlet In the collective housing, when there is a fragile home, there is possibility to receive the above risk from the user of the unspecified number on the Internet through the home and the electric power line on the security to the outside network. 11

12 The security about the control system Security Issues As the lifeline relation, there are much crime prevention facilities and equipment about the human life and the daily life. PLC modem There are very many numbers of the equipment. distribution board The ability of the information processing such as the CPU of the built-in and a resource is small compared with the information machinery. power line distribution board power line There are many long life-time equipments information leakage through power line information leakage through leak radio 12

13 The security about the control system Expected risks Through the network, the lifeline of home may be stopped, or misused. The illegal access which used outdoor power electric outlets If the security is fragile because of a little processing ability, a whole home-network security may be broken through the control system Requested countermeasures Security update techniques for long life-time equipments An access control according to a variety of equipments 13

14 The security about Community Communication Security Issues Key management is complex for communication in each home for communications in a community for simultaneous communications in a home and a community Expected risks If the security of some home in community is fragile, a whole community-network security may be broken through the home Countermeasure For example, management office of community manages every PLC modems in a concentrated manner FTTH power line distribution board distribution board modem Gateway PLC modem PLC modem LAN cable PC 14

15 The Comparison between the power line and the wireles ( ref. Y.Lin et al. A Comparative Performance Study of Wireless and Power Line Networks EEE Comm. Magazine April 2003 ) According to these data, the distance dependence property of throughput differ. However power line communication also has unstableness, and an average range of power line communication is wider. 15

16 The Comparison with other transmission media Network model Area Wired LAN Wireless LAN Bluetooth PLC gateway individual individual individual about 100m about 10m Wider than WLAN in average Measures Firewall i PIN Link Key Built-in equipment fixed mobile mobile /fixed portable /fixed 16

17 Conclusion Compared to wired network, it is difficult for gateway to assure security of PLC(Power Line Communication). Compared to wireless network( e.g. IEEE802.11b), transmission area is more wide, therefore more attackers such as DoS and impersonation may exist. More appliances may connect to PLC home-network, because new cabling is not unnecessary and limitation of location is less. however complex key management is required

18 Group Rekey Distribution Scheme Reliability and real-life customer expectations The existing solution of multicast rekeying still are severely lacking with respect to reliability and real-life customer expectations. We propose a new approach that takes into account different recipient categories and treats each category differently by offering better service

19 Group Rekey Distribution Scheme Preserving members with long-duration membership This paper aims at preserving members with long-duration membership from the impact of rekeying operations caused by members whose membership is shorter.

20 Group Rekey Distribution Scheme Reliability When a new key does not reach its intended recipient because of some packet losses, members affected by these losses will not be able to access future rekeying material.

21 Our proposal for group rekey distribution scheme subject group key update in case of members' joining in or leaving from group. Goal reducing required rekey message size and increasing reliability

22 Key server regroup all members into permanent sub-group and volatile sub-group K 1 K 3 Group key permanent sub-group s key update It dose not generate the special packet for the key update by multiplexing rekey message and non-rekey message volatile sub-group s key update key update only when member change occurs ( the same as LKH ) K 4 K 5 K 6 K 7 M 1 M 2 M 3 M 4 Star Permanent sub-group Tree Volatile sub-group Key Tree Structure

23 multiplexing rekey message and non-rekey message ( e.g. preamble part of packet ) preamble other data usual packet frame exclusive OR Orthogonal code corresponded to update key multiplexed packet frame

24 The analysis about the reliability of key distribution Criterion : rekey message rate ( bits per second : bps) Conventional approach ( approach using FEC ) B' = ( k / T p (C pp / r) + ( k / T v C' vv + k / T p Proposal B = ( k C vv ) / T v + k / T p B/ B' = 1 / ((C p / C v ) (1/r) + 1 ) = 1/3 k key length r FEC's coding rate T p key update period of p-group T v key update period of v-group C pp average rekey number every T p C' vv average rekey number every T v in the conventional C v average rekey number every T v in the proposal C p average rekey number every one second of p-group C v average rekey number every one second of p-group Cp / Cv 1, r = 0.5, Tv /Tp)/ Cvv 0, C'vv / Cvv 1

25 The analysis about the reliability of key distribution Criterion : improved SNR for required reliability (error rate) Conventional approach ( approach using FEC ) improved SNR ( by coding gain ) about 3dB ( coding ratio : 0.5 convolutional coding ) Proposal improved SNR ( by despreading effect ) about 11 db ( orthogonal code length : 12 bit )

26 Conclusion future work Secure update of key table which correspond keys to orthogonal codes, in order to gain backward security analysis of effectiveness in the environment of home-network