A class representing elliptic curve public keys as defined in RFC 7748,
including the curve and other algorithm parameters. The public key is a
particular point on the curve, which is represented using only its
u-coordinate. A u-coordinate is an element of the field of integers modulo
some value that is determined by the algorithm parameters. This field
element is represented by a BigInteger which may hold any value. That is,
the BigInteger is not restricted to the range of canonical field elements.