Creates a new prime finite field of an elliptic curve with the specified
prime {@code p}.
this.p = p;
if (this.p == null) {
throw new NullPointerException(Messages.getString("security.83", "p")); //$NON-NLS-1$ //$NON-NLS-2$
}
if (this.p.signum() != 1) {
throw new IllegalArgumentException(Messages.getString("security.86", "p")); //$NON-NLS-1$ //$NON-NLS-2$
}