Techniques to Prevent Power Analysis on Encryption Hardware CS252 Final Project By Shengliang Song

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Techniques to Prevent Power Analysis on
Encryption HardwareCS252 Final ProjectBy
Shengliang Song Nikita Borisov Professor Jan
Rabaey Kurt Keutzer

• Smart Card
• Differential Power Analysis
• Divide-and-conquer approach

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Smart Card

• Processing Power (Intel 8051, Motorola 6805)
• Data Storage (EEPROM, FLASH, ROM, RAM)
• IO Power Source (Contact, Contactless)

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Smart Cards
B) Inductive Coupling Asynchronous RF/ID and
RF/DC ISO 7816-3 (similar to RS232 operating at
9600 baud with even parity)
Power A) Smart Card Reader Synchronous powered,
clocked and addressed under control of the
outside world
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Differential Power Analysis

• Semiconductor logic gates
• consuming power
• producing electromagnetic radiation
• DPA plaintext or ciphertext gt encryption or
  decryption keys
• Observes m encryption operation
• Captures power traces T1..m1..k (k samples
  each)
• records the ciphertexts C1..m
• Delta D1..k (by finding the difference between
  the averages of the traces for which D(c,b,ks) is
  one and the average of the traces for which
  D(c,b,ks) is zero.)

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Measure a circuits power consumption

• a small (50 ohm) resistor is inserted in series
  with the power or ground input

Vcc
I Vout/R
Vout
R 50 ohm
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DPA Traces
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DEFENSES

• Still being studied
• Balancing computation with complements
• Splitting bits into randomized shares
• Special circuit design techniques
• Randomize order
• Complicated, costly

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Divide-and-conquer approach

• Build a simple ALU which implements sensitive
  operations (ROT, ADD, XOR, Skey)
• Make it power analysis resistant (Continue
  Research IC layer, glu-logical, Computer
  Architecture)
• Design control logical normally (8bit CPU or ROM
  based Machine)

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Control CPU or ROM Based Machine
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ALU SBox

• Basic Units
• ROT
• ADD
• XOR
• SBox
• Shielding will be less complex
• Communication (ALU, Sbox, Ctrl)

SAkey
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ADVANTAGES
IO

• Smaller than an entire cipher
• reduce cost of expensive techniques
• Easier to apply complex design principles
• Model interactions
• Reused

CPU
ALU
SBOX
Skey
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PROBLEMS

• communication between controller and ALU can be
  slow
• Asynchronous (Req, Ack, ALU takes more than one
  clock cycle time)
• Synchronous (ALU need run in a fast clock rate)
• some cipher specific techniques (eg. Randomized
  Sbox lookups) are harder to apply

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References

• Smart Cards http//www.sjug.org/jcsig/others/smar
  t_card.htm
• Differential Power Analysis http//www.cryptograp
  hy.com/dpa/Dpa.pdf