> its presence doesn't prevent message content recovery
The TS is the “salt” & hence defeats rainbow tables, unless somehow it’s feasible to infinitely store them for every combination of message & time for the past/future.
> how hash truncation prevents the attack
It literally deletes half the information you have for the attack. You CANNOT /perfectly/ compute the original text for a truncated hash, you’ll have innumerable clashes.
The problem is that the text that is hashed is not random (like a salted password would be) and the space of all sensible clear texts is much much smaller and possibly amenable to brute force.
Also, storing the hash means that messages are irrefutable.
The TS is the “salt” & hence defeats rainbow tables, unless somehow it’s feasible to infinitely store them for every combination of message & time for the past/future.
> how hash truncation prevents the attack
It literally deletes half the information you have for the attack. You CANNOT /perfectly/ compute the original text for a truncated hash, you’ll have innumerable clashes.
So yes, any attack is impossible/infeasible.