Power Consumption Analysis and Cryptography

1
Power Consumption Analysis and Cryptography

• S. Agagliate CanalTechnologies
• P. Guillot CanalTechnologies
• O. Orcières Thalès Communications

2
The Problem

• A secret is hidden into a chip
• Ex Digital Signature
• How to find the secret?
• Which protection against these attacks?

3
Side Channel Attacks

• Use leak of information
• Power consumption
• Electromagnetic radiation
• Fault provocation
• Computation time

4
Chip consumption
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16
5
XOR gate consumption
x

Known bit
XOR
6
Methods

• SPA Simple Power Analysis
• DPA Differential Power Analysis

7
Counter measures

• Hardware
• Timer
• Bus encryption
• Software
• Algorithms
• Constant timing
• Random Execution

8
Elliptic Curve Cryptosystems

• For digital signature
• Use the computation of Qk.P
• kprivate key
• Pdata
• Advantages
• small key, small signature size
• high security

9
Random Execution

• Variables blinding
• private key k
• base point P
• Randomization of computation algorithm

10
Ternary techniques optimisation
ki ? -1, 0, 1
Q 0 for imax down to 0 Q2Q if ki1 then
QQP if ki-1 then QQ-P Result Qk.P
1111 1000-1 -11 0-1 111101111 1000-1000-1
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
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
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
14
Performances
15
Conclusion

• Power Analysis can reveal secrets
• Solution to interfere with power consumption
• Ex random execution
• Cost computation speed, memory