Determination of the true value of the Euler totient function in the RSA cryptosystem from a set of possibilities
Chuan-Kun Wu, Xiaohan Wang · Electronics Letters · 1993
To attack the RSA cryptosystem, the value of the Euler totient function φ(n) can be guessed (with a probabilistic algorithm) instead of factorising modulus n. The Letter proves that among the possible values of φ(n), only that satisfying 2x ≡ 1(mod n) is the true value, i.e. x = φ(n), under some reasonable assumptions.