I wish that restic supported asymmetric keys. I'm uncomfortable storing the key alongside the backup tool, even if it just gets injected at runtime. If a nefarious party gets the key all my backups from that key are vulnerable.

I suspect that it's probably hard to add that functionality because you can't do the deduplication without decrypting the prior backups (or at least an index). That would also explain the memory usage JoshTriplett mentions.