-th bits of the input [3]. While T-functions are often used to create long-period sequences, improper implementation can lead to significant linear vulnerabilities. Key Vulnerabilities
Compare the resulting bit with the observed ciphertext/keystream bit. ti_moe_more
, the state can be recovered one bit at a time starting from the Least Significant Bit (LSB) [4, 6]. -th bits of the input [3]
: The state size or the complexity of the mixing function is insufficient to prevent a guess-and-determine attack or a simple breadth-first search on the bit transitions [3, 5]. Solution Strategy (Write-up) , the state can be recovered one bit
: Since there may be multiple candidates for a bit that satisfy the equation temporarily, use a recursive search or a queue-based approach to find the state that consistently produces the correct keystream for the entire length of the flag [3, 4].
: Observe that the LSB of the keystream is directly tied to the LSB of the initial state. Bit-Stepping : Assume the first bits of the state are known. Simulate the T-function for the next bit (
The vulnerability in stems from the predictable bit-propagation within the T-function: Bit-by-Bit Leakage : Because the