[PULL] monitor incoming transactions for spends from self

[Pieter Wuille]

Bitcoin currently does not check whether transactions received from the P2P network contain spends from your own addresses. Presumably because this was considered an impossible situation, but it happens when people copy wallet.dat files around.

This checking is done anyway when rescanning, and a full rescan of the entire realnet blockchain currently takes 11s on my old laptop, so I think the overhead of doing this check on incoming transactions as well, is very limited.

This issue was mentioned here before: http://bitcointalk.org/index.php?topic=3638.msg52145#msg52145.

Pull request is here: https://github.com/bitcoin/bitcoin/pull/157

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[khal]

Your patch is usefull when you have two copies of your wallet running at the same time ?

For an offline wallet, a partial rescan is needed with your complementary patch : https://github.com/bitcoin/bitcoin/pull/152

Good job

[Pieter Wuille]

Basically yes, both cover part of the problem of using the same key(s) on different installations.

One problem still remains though: if you try to spend coins from node A, while node B already spent them without A knowing about it, it will happily create a transaction and assume it will be accepted by the network, which it won't, possibly leaving you with a corrupted wallet forever. So, even though some wallet-sharing issues are already covered, it can still be dangerous.