It is fairly baffling why you'd choose RSA with 512 bit keys; as noted elsewhere I assume this is about the size of the signature. However, a PKCS#1 signature f

It is fairly baffling why you'd choose RSA with 512 bit keys; as noted elsewhere I assume this is about the size of the signature. However, a PKCS#1 signature for a 512 bit RSA key is 64 bytes, which is the same size as an ECDSA signature for, say, a NIST P-256 key and you're giving up an enormous amount of security by choosing RSA even vs entirely mainstream stuff like ECDSA.