As far as I understand ECDSA keys are smaller than RSA because all of the value of the ECDSA (up to a high number) are valid private keys.
Is there any method of compressing RSA keys, based on some form of description of the key?
e.g. This is the $M^{\text{th}}$ possible value of $n$, given that $e = E$ and $A \leq n < B$.
