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Old 2021-07-31, 02:13   #20
Dr Sardonicus
 
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Feb 2017
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Quote:
Originally Posted by RomanM View Post
<snip>
b=mod(u^n,p); a=mod(b^n,p)
b^2-a is a multiple of p for any integer n>0, I don't know the behavior of epsilon for every n, but seems that algorithm work only if n=2.
Do you mean b^n - a?

Another issue arises if n > 2, particularly for odd n > 2. Even if p is prime, if gcd(n, p-1) = 1, every residue mod p is an nth power residue. For n = 3, this is the case for every prime p congruent to 2 (mod 3).
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