Find order of an Elliptic Curve over Gaussian Integer

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While the quotient you constructed is a valid object, it seems to be not the optimal way to construct the respective mathematical object. Apparently, general quotients of the Gaussian integers ZZ[I] currently have only barebones functionality; SageMath doesn't even know when they are finite. However, since p is prime (hence maximal) in ZZ[I] we can compute the residue_field instead (which is a much better implementation of the quotient):

p = 107927
G = ZZ[I]
J = G.ideal(p)
Q.<a> = G.residue_field(J)

A = (95385+100114*a)
B = (18724+61222*a)
E = EllipticCurve(Q,[A, B])
print(E)
print(E.cardinality())

It outputs:

Elliptic Curve defined by y^2 = x^3 + (100114*a+95385)*x + (61222*a+18724) over Residue field in a of Fractional ideal (107927)
11648283482

as you predicted.

Alternatively, making use of the third isomorphism theorem:

p = 107927
Q.<a> = GF(p^2, modulus=x^2+1)

This is possibly even faster.