Download - Power Consumption Analysis and Cryptography
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Sandrine AGAGLIATE, FTFC 2003 1
Power Consumption Analysis and Cryptography
S. Agagliate Canal+TechnologiesP. Guillot Canal+TechnologiesO. Orcières Thalès Communications
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Sandrine AGAGLIATE, FTFC 2003 2
The Problem
A secret is hidden into a chipEx: Digital Signature…
How to find the secret? Which protection against these attacks?
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Sandrine AGAGLIATE, FTFC 2003 3
Side Channel Attacks
Use leak of information Power consumption Electromagnetic radiation Fault provocation Computation time
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Sandrine AGAGLIATE, FTFC 2003 4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Chip consumption
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Sandrine AGAGLIATE, FTFC 2003 5
+
x
Known bit
XOR
XOR gate consumption
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Sandrine AGAGLIATE, FTFC 2003 6
Methods
SPA = Simple Power Analysis DPA = Differential Power Analysis …
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Sandrine AGAGLIATE, FTFC 2003 7
Counter measures
HardwareTimerBus encryption …
SoftwareAlgorithms
Constant timing Random Execution
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Sandrine AGAGLIATE, FTFC 2003 8
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
P1P2
P3=P1+P2
baxxyE K 32/ :
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Sandrine AGAGLIATE, FTFC 2003 9
Random Execution
Variables blinding private key k base point P
Randomization of computation algorithm
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Sandrine AGAGLIATE, FTFC 2003 10
Ternary techniques: optimisation
i
iikk 2
max
0
ki { -1, 0, 1 }
1111 = 1000-1-11 = 0-1111101111 = 1000-1000-1
Q := 0for i:=max down to 0
Q:=2Qif ki=1 then Q:=Q+Pif ki=-1 then Q:=Q-P
Result Q=k.P
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Sandrine AGAGLIATE, FTFC 2003 11
Binary transducer ternary
1 : 1 0
0
3
1
2
0 1
-1
0 : 00 : 0 1
0
0 : -1 0
1
1 : 0 -1
1 : 0
-1 0
0
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Sandrine AGAGLIATE, FTFC 2003 12
Sub-optimal alternate automaton
1 : 1 0
0 1
2
0 1
-1
0 : 00 : 0 1
1
1 : 0
0
0 : -1
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Sandrine AGAGLIATE, FTFC 2003 13
1 : 1 0
0
3
1
2
0 1
-1
0 : 00 : 0 1 / p
0 / q
0 : -1 0
1
1 : 0 –1 / r
1 : 0
-1 0
0 0 : 1 -1 / 1 - p
0 : -1 / 1 - q
Randomized automaton
1 : -11 / 1 -r
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Sandrine AGAGLIATE, FTFC 2003 14
Performances
2,2%2,1%Gain / previous work without DPA countermeasures
10,6%10,7%Loss / first automaton
300160Key size
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Sandrine AGAGLIATE, FTFC 2003 15
Conclusion
Power Analysis can reveal secrets Solution: to interfere with power
consumption Ex: random execution
Cost : computation speed, memory…