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 2022-03-11, 15:54 #1 paulunderwood     Sep 2002 Database er0rr 22·1,063 Posts Strengthening Damg ̊ard and Frandsen, and Khashin Strengthening Damg ̊ard and Frandsen[1], and Khashin[2] I propose the test: {tst(n,c)= Mod(c,n)!=-1&& kronecker(c,n)==-1&& Mod(c,n)^((n-1)/2)==-1&& Mod(Mod(x+1,n),x^2-c)^(n+1)==1-c;} The Frobenius part's squaring during left-right binary exponentiation can be computed in 2 Selfridges for small c [2:2.2]: (s*x+t)^2 == 2*s*t*x + (t+c*s)*(t+s) - (c+1)*s*t, where s and t are intermediate values. Multiplication by the base x+1 is: (s*x+t)*(x+1) = (t+s)*x + c*s+t. Therefore the test is 1+2 Selfridges and has no known counterexamples so far... Do any of the authors mention the addition of the Euler PRP test? [1] An Extended Quadratic Frobenius Primality Test with Average Case Error Estimates & Ivan Bjerre Damg ̊ard Gudmund Skovbjerg Frandsen, https://eprint.iacr.org/2001/102.pdf [2] Counterexamples for Frobenius primality test, Sergey Khashin, https://arxiv.org/pdf/1307.7920.pdf Edit: In order to prevent cyclotomic polynomials I add Mod(c,n)!=-3 and Mod(c,n)!=-1/3, the latter where gcd(3,n)==1 However a counterexample is [n, c]=[79786523, 2982522]. Last fiddled with by paulunderwood on 2022-03-11 at 20:29

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