What is the performance difference of pki to symmetric encryption?

Question

We are looking to do some heavy security requirements on our project, and we need to do a lot of encryption that is highly performant.

I think that I know that PKI is mu

Answer 1

Practical PKI-based encryption systems use asymmetric encryption to encrypt a symmetric key, and then symmetric encryption with that key to encrypt the data (having said that, someone will point out a counter-example).

So the additional overhead imposed by asymmetric crypto algorithms over that of symmetric is fixed - it doesn't depend on the data size, just on the key sizes.

Last time I tested this, validating a chain of 3 or so X.509 certificates [edit to add: and the data they were signing] was taking a fraction of a second on an ARM running at 100MHz or so (averaged over many repetitions, obviously). I can't remember how small - not negligible, but well under a second.

Sorry I can't remember the exact details, but the summary is that unless you're on a very restricted system or doing a lot of encryption (like if you want to accept as many as possible SSL connections a second), NIST-approved asymmetric encryption methods are fast.