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Published byMayra Maddox Modified over 2 years ago

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Smart Card security analysis Smart Card security analysis Marc Witteman, TNO

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Do we need smart card security?

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What are the threats ? disclosure Confidentiality:unauthorized disclosure of information sender receiver modification Integrity:unauthorized modification of information Authenticity:unauthorized use of service

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Whats inside a smart card ? CPU RAM test logic ROM EEPROM serial i/o interface security logic databus

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Smart card security evaluations logical analysis: software internal analysis: hardware side channel analysis: both hw and sw

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Logical analysis Communication Functional testing Protocol analysis Code review

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InternalAnalysis

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Internal analysis tools Etching tools Optical microscope Probe stations Laser cutters Scanning Electron Microscope Focussed Ion Beam System and more…….

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Reverse engineering

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Staining of ion implant ROM array

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Sub micron probe station

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Probing with eight needles

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FIB: fuse repair

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Side channel analysis Use of hidden signals –timing –power consumption –electromagnetic emission –etc.. Insertion of signals –power glitches –electromagnetic pulses

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Power consumption in clock cycle peak slope time I ddq area shape

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Power consumption in routines

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Power consumption in programs

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Timing attack on RSA RSA principle: –Key set e,d,n –Encipherment: C = M e mod n –Decipherment: M = C d mod n RSA-implementation (binary exponentiation) –M := 1 –For i from t down to 0 do: M := M * M If d i = 1, then M := M*C

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Timing Attack on RSA (2)

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Differential Power Analysis Assume power consumption relates to hamming weight of data Subtract traces with high and low hamming weight Resulting trace shows hamming weight and data manipulation

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Fault injection on smart cards Change a value read from memory to another value by manipulating the supply power: Threshold of read value A power dip at the moment of reading a memory cell

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Differential Fault Analysis on RSA Efficient implementation splits exponentiation: d p = d mod (p-1) d q = d mod (q-1) K = p -1 mod q M p = C d p mod p M q = C d q mod q M = C d mod n = ( ( (M q - M p )*K ) mod q ) * p + M p

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DFA on CRT Inject a fault during CRT that corrupts M q : M q is a corrupted result of M q computation M = ( ( (M q - M p )*K ) mod q ) * p + M p subtract M and M: M - M = (((M q - M p )*K) mod q)*p - (((M q - M p )*K) mod q)*p = (x 1 -x 2 )*p compute Gcd( M-M, n ) = Gcd( (x 1 -x 2 )*p, p*q ) = p compute q = n / p

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Conclusions Smart cards can be broken by advanced analysis techniques. Users of security systems should think about: –What is the value of our secrets? –What are the risks (e.g. fraud, eavesdropping) –What are the costs and benefits of fraud? Perfect security does not exist!

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For information: TNO Evaluation Centre Marc Witteman PO-Box GA Delft, The Netherlands Phone: Fax:

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