Common-modulus RSA attack
= Common-modulus RSA attack
= RSA common-modulus attack
{c}
{synonym}
If the same invertible message $m$ is sent under one RSA modulus with coprime public exponents $e_1,e_2$, choose integers $a,b$ with $ae_1+be_2=1$. From $c_i=m^{e_i}\pmod N$ one recovers
$$
m\equiv c_1^ac_2^b\pmod N,
$$
using modular inverses for negative exponents.