I need to do some plumbing in a special remote. What is the best way to get the filenames of all the chunks belonging to a key? From https://git-annex.branchable.com/internals/ I know that .log.cnk stores size and number of chunks. And that part of the cipher in remote.log is used as the HMAC encryption key.

I found that I can use openssl to calculate the HMAC, but what exactly do I need to feed it?

echo $PAYLOAD | openssl sha512 -hex -mac HMAC -macopt hexkey:$KEY_HEX

Or is there a git-annex plumbing command that I overlooked?