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Power Consumption Analysis and Cryptography

Power Consumption Analysis and Cryptography. S. Agagliate Canal+Technologies P. Guillot Canal+Technologies O. Orcières Thalès Communications. The Problem. A secret is hidden into a chip Ex: Digital Signature … How to find the secret?

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Power Consumption Analysis and Cryptography

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  1. Power Consumption Analysis and Cryptography S. Agagliate Canal+Technologies P. Guillot Canal+Technologies O. Orcières Thalès Communications Sandrine AGAGLIATE, FTFC 2003

  2. The Problem • A secret is hidden into a chip • Ex: Digital Signature… • How to find the secret? • Which protection against these attacks? Sandrine AGAGLIATE, FTFC 2003

  3. Side Channel Attacks • Use leak of information • Power consumption • Electromagnetic radiation • Fault provocation • Computation time Sandrine AGAGLIATE, FTFC 2003

  4. Chip consumption 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Sandrine AGAGLIATE, FTFC 2003

  5. XOR gate consumption x + Known bit XOR Sandrine AGAGLIATE, FTFC 2003

  6. Methods • SPA = Simple Power Analysis • DPA = Differential Power Analysis • … Sandrine AGAGLIATE, FTFC 2003

  7. Counter measures • Hardware • Timer • Bus encryption • … • Software • Algorithms • Constant timing • Random Execution Sandrine AGAGLIATE, FTFC 2003

  8. P2 P1 P3=P1+P2 Elliptic Curve Cryptosystems • For digital signature • Use the computation of Q=k.P k=private key P=data • Advantages • small key, small signature size • high security Sandrine AGAGLIATE, FTFC 2003

  9. Random Execution • Variables blinding • private keyk • base pointP • Randomization of computation algorithm Sandrine AGAGLIATE, FTFC 2003

  10. Ternary techniques: optimisation ki  { -1, 0, 1 } Q := 0 for i:=max down to 0 Q:=2Q if ki=1 then Q:=Q+P if ki=-1 then Q:=Q-P Result Q=k.P 1111 = 1000-1 -11 = 0-1 111101111 = 1000-1000-1 Sandrine AGAGLIATE, FTFC 2003

  11. Binary transducer  ternary 0 0 1 1 0 1 0 : 0 1 0 : 0 1 : 1 0 0 : -1 0 0 1 : 0 3 2 1 : 0 -1 -1 0 -1 Sandrine AGAGLIATE, FTFC 2003

  12. Sub-optimal alternate automaton 0 0 1 1 0 1 0 : 0 1 0 : 0 1 : 1 0 0 : -1 1 : 0 2 -1 Sandrine AGAGLIATE, FTFC 2003

  13. Randomized automaton 0 0 1 0 : 1 -1 / 1 - p 1 0 1 0 : 0 1 / p 0 : 0 1 : 1 0 0 : -1 0 0 : -1 / 1 - q 1 : 0 0 / q 3 2 1 : 0 –1 / r -1 0 -1 1 : -11 / 1 -r Sandrine AGAGLIATE, FTFC 2003

  14. Performances 300 Key size 160 Loss / first automaton 10,7% 10,6% Gain / previous work without DPA countermeasures 2,1% 2,2% Sandrine AGAGLIATE, FTFC 2003

  15. Conclusion • Power Analysis can reveal secrets • Solution: to interfere with power consumption • Ex: random execution • Cost : computation speed, memory… Sandrine AGAGLIATE, FTFC 2003

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