Tieyan Li, Hongjun Wu, Feng Bao, Henry Lee'

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Flagship project SmartCondo-gtSecureSensor
Design SenSec with improvement cryptanalysis
Tieyan Li, Hongjun Wu, Feng Bao, Henry
Lee. InfoComm Security Department
(ICSD) Institute for Infocomm Research (I2R) 9th,
Jul. 2004
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Outline

• Improvement and cryptanalysis SenSec (formerly
  TinySec)
• Improvement
• Cryptanalysis
• Packet format
• Analyze overheads
• Analyze performance
• Source code (to be changes)
• New component graph
• In proceeding

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Improvement

• TinySec
• Optional design (No TinySec, TinySec-Auth
  (default), TinySec-AE). Confusing
• Using a block cipher for both encryption
  authentication is smart. Processing encryption
  authentication separately is not wise
• Assuming Msg gt 8 bytes. How to process smaller
  msg
• SenSec
• AE by default (SenSec-AE). Clearing
• Completing encryption authentication in one
  process. Saving energy (-2)
• Assuming all msg lengths (including lt 8 bytes).
  Padding additional bytes with msg length nlt8
  bytes

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Cryptanalysis

• The IV in TinySec
• Each sensor keeps an IV for every destination
  address
• If too many destination addresses, high memory
  consumption
• If limited memory space, same IV being used
  repeatedly
• TinySec -- assume each sensor communicate with
  only a few sensors
• (say, 4 or 5). Not general.
• SenSec
• Keep the one byte group ID (distinguish the
  group messages)
• Each sensor only needs to keep one IV
• No restriction on the number of sensors in a
  group to communicate with each other (group id,
  one byte, differentiate the motes in the
  different groups)

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SenSec (Packet format)
Old packet (CRC) 7 b
Authentication Only (TinySec-Auth) 8 b
Authentication, Encryption (TinySec-AE) 12 b
IV
Dest (2)
AM (1)
Len (1)
Data (0..29)
MAC (4)
Ctr (3)
Grp (1)
(SenSec) 12 b
IV
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SenSec (Predicted Overhead)
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SenSec (Performance Summary)
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SenSec (Sources need to be changed)

• tos.interfaces  (may not be the same name)
• TinySec.nc  _at_author Tieyan Li   
• TinySecControl.nc  _at_author Tieyan Li 
• MAC.nc  _at_author Hongjun Wu, Interface to
  compute a message authentication code.  
• BlockCipher.nc  _at_author Hongjun Wu   
• BlockCipherInfo.nc     _at_author Hongjun Wu
• BlockCipherMode.nc  _at_author Hongjun Wu, Presents
  an encryption mode interface on type of the
  BlockCipher interface
• tos.lib.TinySec  (may not be the same name)
• AMStandardTinySec.nc  _at_author Tieyan Li
• CBCMAC.nc  _at_author Hongjun Wu   
• CBCModeM.nc  _at_author Hongjun Wu, Implements
  Cross Block Chaining mode.   
• Security.nc  _at_author Hongjun Wu   
• SecurityM.nc  _at_author Hongjun Wu   
• SkipJackM.nc  _at_author Hongjun Wu  
• TinySecC.nc  _at_author Tieyan Li
• TinySecM.nc  _at_author Tieyan Li

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SenSec (Component graph)
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In proceeding
Available at http//www.i2r.a-star.edu.sg/icsd/Se
cureSensor/papers/Secure-Sensor-0708.ppt
Thank you! Q A