Function franklin_reiter_attack 

pub fn franklin_reiter_attack(
    e: u32,
    r: &BigInt,
    c1: &BigInt,
    c2: &BigInt,
    n: &BigInt,
) -> Option<BigInt>

Franklin–Reiter related-message attack: recover m from ciphertexts of two LINEARLY RELATED messages m and m + r (known r) under the same modulus N and a small public exponent e. Both g₁(x) = xᵉ − c₁ and g₂(x) = (x + r)ᵉ − c₂ have the root x = m mod N, so their GCD over (ℤ/N)[x] is the linear factor x − m, and m is read straight off it. The lens: two ciphertexts sharing a hidden root, extracted by polynomial GCD.