Digital Certificate - changing encryption algorithm

Question

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?

Answer 1

It needs to be recreated. Public and private keys are made in pairs at the same time.