# Gavin Andresen
# 2011-02-02 16:10:24
# https://bitcointalk.org/index.php?topic=3092.msg43625#msg43625

How do you think the code should deal with the issue of "a fixed txid might no longer be valid" ?  Or transactions that you THOUGHT had N confirmations and were in a block with timestamp T are re-organized to have M confirmations and are in a block with timestamp T2 ? @p{par}

tcatm and I chatted in IRC about this problem@p{--} he has the problem of how to keep the Javascript GUI (which shows you ever transaction) up-to-date. @p{par}

Seems like you really want an efficient way of asking "Do I know about exactly the same set of transactions as bitcoind" (either for the entire wallet or for an account).  That's assuming transaction data can't change (somebody double-check that assumption for me@p{--} if the transaction data changes, then the txid changes... I think). @p{par}

That led to some brainstorming of computing a hash of all transaction ids (maybe just XOR them all together).  Or maybe something more complicated like a merkle tree...   but that seems like overkill. @p{par}

Is there a good, simple solution to synchronizing "I have this set of stuff, give me everything I don't have" ?