When choosing the public key for ElGamal, $\alpha$ must be chosen as a primitive mod p. What if $\alpha$ is not a primitive root ? How will it influence the encryption and decryption ?

  • $\begingroup$ nice link $\endgroup$
    – kelalaka
    Commented Oct 25, 2018 at 22:05

1 Answer 1


Everything works, except the key and signature space, reduced greatly;

The result is that the signature space (when the key is used for signing) or the public key space (when the key is used for encryption) may be greatly reduced from its expected size of log(p) bits, possibly down to 1 bit (the worst case if the order of g is 2)1.

It not hard to detect a $g$ is the generator or not.


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