Custom certificate as proof of transaction

Question

I'm developing a site where a user conducts a given transaction and once completed, the user is issued with a 'secure certificate'. The certificate serves as proof of the transaction and the user is able to upload the certificate at a later stage, to view the details of the transaction.

At the moment I'm using a custom XML document with encrypted fields. It works perfect, but I would like a standardized approach, such as an X.509 certificate. I'm no encryption expert, but from what I gather, X.509 is more geared towards SSL issued by a CA.

Is it possible to create your own valid valid CRT file? As a test, I created a CRT file with the example provided on WikiPedia. However, when I open the file in Windows I get this warning: Invalid Public Key Security Object File - This file is invalid as the following: Security Certificate.

Not having much luck here, so time to ask the experts. What direction should I be heading in? Any guidance would be greatly appreciated.

Answer 1

This doesn't really sound like a job for Asymmetric encryption. All you want to do is create some data that only you will ever be able to read? That's a job for plain old fashioned Symmetric encryption. The 'right' algorithm to use depends on your security vs performance needs, but there are libraries for just about any language you could be using.