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While searching for off-the-chain BTC txs I came up with small and simple idea that I want to share and discuss:
Set up two machines, master and slave - bookkeeper and wife, bookkeeper will make basic accounting, his wife will scream loudly if he pass out or he lost hist mind. Tech side:
1. Two instances running in cloud with good reputation.
2. Instance images are closed to any internal administration (no ssh... cpanel hehe), only transactions and bookkeeper-wife communication and btc network, both publicly(or widely) auditable. Configured with no persistent storage so any reboot or hardware failure will lead to erasing all instance data.
3. Bookkeeper's software, running in ramdisk, creates keypairs at startup, receives BTC via network, creates user account (tied to sender btc address) credited with received coins and takes account creation fee. Then user can register another accounts(with fee) or transfer some coins to other accounts. There is no transactions history at his side, all done with atomic balance updates.
4. Along with each BTC network deposit, bookkeeper appends new input to private transaction.
5. When sender-receiver(internal) balances change - private transaction's outputs matching their balances are updated.
6. After each priv-tx update, priv-tx is immediately send to second instance - bookkeeper's wife.
7. Private transaction is broadcasted to btc network in three cases:
a) publicly known and agreed bookkeper's end-of-life is reached (bkkeeper broadcasts)
b) bookkeeper unexpectedly died, or at least he stopped responding to his wife (wife broadcasts)
c) wife is dead or got mad (bkkeeper broadcasts)
8. If all instances job was done good (7.a) the final transaction contains also output for instance holder to collect fees (so there are actually two priv-txs kept whole time, one with fees to the admin and one without)
Both instances should be hosted by different providers or at least at different zones, then the probability that the priv-tx won't be broadcasted(all btc would be lost then) is minimal.
This simple model should be very useful for small communities but surely can scale up and get additional layers to match other use cases. And there is no transactions history at all (of course bookkeeper can work with one in his RAM).
Needed parts are:
- reliable software
- cloud provider matching needs(stable, instance audits, data privacy)
So, what do you think about it?
P.S. Sorry for my ~English
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Here is first sketch, in Java
https://github.com/kactech/offchain/blob/master/blind-bookkeeper/src/main/java/com/kactech/offchain/BlindBookkeeper.java
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2013-07-24 - sketch update
