Creates an RSA key file with the following lines 1 Public Modulus N 2 Private Exponent D 3+ Private Primes (depending on COMM_NOF_PRIMES).

Note that this is the default public exponent set by Golang in rsa.go See https://github.com/golang/go/blob/6269dcdc24d74379d8a609ce886149811020b2cc/src/crypto/rsa/rsa.go#L226.