So usually the Diffie-Hellman key is 2048 bits as I understand but my computer can barely calculate a 10 digit number. What are some common numbers in Diffie-Hellman?
Here is my code that's suuuper slow:
$gen = 77;
$mod = 517165;
$saltA = 1233217;
$saltB = 5173123;
$calculatedSecretKeyA = gmp_mod(gmp_pow($gen, $saltA), $mod);
$calculatedSecretKeyB = gmp_mod(gmp_pow($gen, $saltB), $mod);
$calcKeyA = gmp_mod(gmp_pow($calculatedSecretKeyB, $saltA), $mod);
echo $calculatedSecretKeyB . "^" . $saltA . "" . " mod " . $mod . " = " . $calcKeyA;
$calcKeyB = gmp_mod(gmp_pow($calculatedSecretKeyA, $saltB), $mod);
echo $calculatedSecretKeyA . "^" . $saltB . "" . " mod " . $mod . " = " . $calcKeyB;
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.