I know you shouldn’t roll your own crypto and generally its not a good idea to implement (and then deploy) any extensively tested and recommended algorithms by yourself either.
I have already seen this question, and as far as I understand, the main problem with implementing things yourself is that you will probably remain vulnerable to a host of side-channel attacks.
But suppose I have already implemented AES (just for fun and as a learning experience). What if I now use that implementation for simply encrypting files locally (and then perhaps back them up on the cloud or on removable media)? Since nobody other than me would be using the implementation, most of the side channel attacks would not apply. For instance, since no attacker can request an encryption/decryption (the way it works with a server), no timing attack can be carried out. Would this scenario be sufficiently secure?
In other words would using my own implementation of AES provide security for data at rest or will using it still be a stupid idea?