Random Fault Attacks on a Class of Stream Ciphers

Algorithm 1

Algorithm for Random Fault Attack on Certain Ciphers.

1: Load key and initialization vector and perform the initialization phase.

2: Encrypt plaintext to compute the fault free ciphertexts and .

3: Repeat Step 2 but inject a random multi-byte fault in the state word .

Proceed to compute the faulty ciphertext words and .

4: Observe the faulty and fault free ciphertext words and apply Equation (10)

to recover the value of the random fault .

5: For any bits in the random fault equal to one, observe the values in the

corresponding bit positions in the faulty and fault free ciphertext and apply

Equation (11) to recover the corresponding bits of .

6: Repeat steps 3 to 5 until all of the bits in are recovered.