I have a distributed application consisting of many components that communicate over TCP (for examle JMS) and HTTP. All components run on internal hardware, with internal IP addresses, and are not accessible to the public.
I want to make the communication secure using SSL. Does it make sense to purchase signed certificates from a well-known certificate authority? Or should I just use self-signed certs?
My understanding of the advantage of trusted certs is that the authority is an entity that can be trusted by the general public - but that is only an issue when the general public needs to be sure that the entity at a particular domain is who they say they are.
Therefore, in my case, where the same organization is responsible for the components at both ends of the communication, and everything in between, a publicly trusted authority would be pointless. In other words, if I generate and sign a certificate for my own server, I know that it's trustworthy. And no one from outside the organization will ever be asked to trust this certificate. That is my reasoning - am I correct, or is there some potential advantage to using certs from a known authority?
There is no need for you to use an external public CA for a closed community project. In many larger organisations they operate an internal PKI to issue certs for internal projects like this. An advantage of using a PKI is that you can setup a trust relationship between the various components based on a single securely distributed root certificate / trust anchor.
However, if the project allowed internal users to connect securely to an internal service via their web browser you may want to consider using a public CA issued cert. The alternative is to make sure that every browser that may need to connect to your service trusted your root cert; this is to prevent browser warning messages.
I'd say it's reasonably safe, unless you think a ninja infiltrator is going to swap your server on you.
The 3rd party is there to make it harder to just 'up & generate' a new cert. Someone could re-create a self-signed cert on a new machine with the same details, it wouldn't be the same cert, you'd have to add an exception for it too, but your users probably wouldn't know the difference.
As long as your system is running inside your group and there are no plans to expand it (and plans do change, so keep that in mind), it is just fine to setup your own simple PKI infrastructure.
If you do end up expanding beyond your organization, all you need to do is distribute your root certificate to the parties you will be communicating. This gives actually a fine grained control to your partners how much trust they want to put in you vs the public CA infrastructure.
