CAs sort of have the same problem. You can condense the problem to a subset of keys though with a verification chain. When posted, a sequence number + key + ms

CAs sort of have the same problem. You can condense the problem to a subset of keys though with a verification chain. When posted, a sequence number + key + msghash + verification result + last verification result is posted publicly. That makes a block. I supposed we could call that a blockcha.... dangit. I almost said the forbidden word.