The title says it all really...let's say I have a packet of data that one of my applications needs to store encrypted with a public key (RSA, say, with the private key kept elsewhere). Let's say the application also then needs a way of determining if said packet has already been stored, so I combine it with a randomly generated salt and save the hash of packet+salt so I can check it later (e.g. MD5). Does storing the combination of these three pieces of data...i.e. encrypted packet, the salt and the hash....result in data that is significantly less secure than the encrypted packet alone?
I realize "significantly less secure" is an arbitrary metric. I'm not after anything military grade (for want of a better nonsensical term), I just want to make sure I'm not doing anything overtly silly.