php - How does the computer calculate or store diffie hellman values?

Question

question from:https://stackoverflow.com/questions/66069915/how-does-the-computer-calculate-or-store-diffie-hellman-values

Answer 1

Use gmp_powm

gmp_powm ( GMP|int|string $num , GMP|int|string $exponent , GMP|int|string $modulus ) : GMP

for the below lines.

$calculatedSecretKeyA = gmp_powm($gen, $saltA, $mod);

$calculatedSecretKeyB = gmp_powm($gen, $saltB, $mod);

$calcKeyA = gmp_powm($calculatedSecretKeyB, $saltA, $mod);
    
$calcKeyB = gmp_powm($calculatedSecretKeyA, $saltB, $mod);

It uses the modular form of square-and-multiply technique. The intermediate values will never exceed mod^2. Also, it has O(log n) complexity.