It&#x27;s called index calculus[1]. Basically, it allows you to do a (huge) amount of work that can be factored out from breaking specific DH exchanges, as long as the same prime is used. Since finding good DH primes is far more expensive than coming up with good primes for RSA, these primes tend to be reused on a massive scale.<p>[1]: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Index_calculus_algorithm" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Index_calculus_algorithm</a>