[MertsA]

In general, yes, an append only log might be weakly "append only". If you want a cryptographic approach look at how forward secure sealing works with systemd. Basically you make a cryptographic ratchet on the system doing the logging such that given some arbitrary key you can find out what the next key is but not the previous one. You generate a verification key that you take off of the system in question at the start and the verification key can be used to efficiently check any part of that series. During operation you sign the log segment you just wrote out on some regular interval and then ratchet the key forward and delete the old key in memory to where even if the system was completely compromised it no longer holds a key that could rewrite the previous log segment.