Jörn-Marc Schmidt joern-marc.schmidt@iaik.tugraz.at
Fault Injection Plaintext Faulty Ciphertext But how to inject a fault?
Fault: • Injection • Model • Exploitation
Non-invasive Device is not altered physical Semi-invasive De-packaging, no electrical contact Invasive No limits
Active Passive (Fault Attacks) (Observing Attacks) Glitch attacks, Power Side-Channel Non-Invasive Spikes, … Attacks Optical Fault Injection, Optical inspection Semi-Invasive … (ROM, …) Permanent circuit Invasive Probing, … changes, …
Oscilloscope Microscope Probing station Focused Ion Beam (FIB)
Class I Clever Outsider Class II Knowledgeable Insider Class III Funded Company
Decapsulation Procedure: 1. Mill a hole 2. Etch with Fuming Nitric Acid 3. Clean with Ultrasonic treatment in Acetone
Light creates electron / hole pair • • Near np junction: hole moves to p, electron to n region • Results in current and maybe a transition of a transistor • Called Optical Beam Induced Current (OBIC) Light Electron Hole n region p region
• Fault Type – Transient – Permanent – Destructive • Timing • Precision (Bit, Byte, Word) • Set, Flip, Program Flow..
d d = Sig CRT ( M mod p , M mod q ) mod pq d = M mod pq a random fault d d = + δ Sig CRT ( M mod p , M mod q ) mod pq d = + ∆ M p mod pq = − p GCD ( Sig Sig , pq ) p, q: large primes M: message to sign d: secret key
Manipulation of: – Loops – Checks � Repeat transmit (*MSG_address); MSG_length+ + ; MSG_address+ + ; until(MSG_length= = 5); �
… MixColumns • Alter Ciphertext AddRoundKey • Set Bit before SB • Fault before MC SubBytes ( 𝜀 , 0,0,0) ShiftRows AddRoundKey Ciphertext
Fault Injection Power Consumption Timing Electromagnetic Emanation Error Messages
0 = R 0
• An adversary can inject more than a single fault. • Can we do better than doubling? • How to built efficient side-channel and fault countermeasures?
• Fault attacks are powerful • Possible attacks depend on adversary • Stick to realistic fault models
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