Sorry if this is a silly question, but I'm new to all these certificates stuff :)

Let's say I have a digital certificate issued by my company (for email) with:

- Signature algorithm: md5RSA
- Public Key: RSA (512 bit)

Is it possible to convert this to use:

- Signature algorithm: sha1RSA
- Public Key: RSA (2048 bit)

Or it needs to be recreated by my issuer with the new settings?