I'd like it be be in the main client, but I'd like it to be called "privacy mode", as opposed to "advanced view", for its educational effect. 

For further educational effect, privacy mode could enable informational warnings that let you know which addresses/identites are being linked during a transaction.

If address labels have multiple entries: identity, one to distinguish same-identity addresses, and an "Is Reused?" checkbox for send addresses that you know or expect get reused with multiple people, then the messages generated can be much more personalized and succinct, and will hit home better.

Imagine if when you tried to send some bitcoins you got a warning like this:


Or maybe replace ShadyDude with Wikileaks' public address, and RichMistress with BusinessIPatronize (who happens to reuse the same address and needed to send you a refund one time, and who is now being subpoenaed by the Stasi into identifying you as the owner of the address the sent the refund to in order to prove you donated to Wikileaks).

Clearly address reuse is really bad for privacy, and the consequences are not internalized to the address re-users, so I think new address requests (and labeling) should be automated for all clients, not just privacy-conscious ones.

Sorry if this is obvious or flawed - I'm new to this stuff - but here's an idea for how to do this:

This can be done by having a contacts list, and a single master public key from each of their contacts, from which they can deterministically derive as many addresses as they want.  These addresses can't be associated by outsiders as long as the master public key is kept secret.  See this post by Stefan http://forum.bitcoin.org/index.php?topic=19137.msg318989#msg318989 and the one below by gmaxwell about choosing a sequence of serial numbers for how it might be implemented: .

Of course lost master private keys will be a problem, but this can be mitigated by users having (untrusted) storage servers that serve the master public keys to their contacts (the same one that syncs your everyday-use wallet between devices?).  This way they can be easily changed at any time, all at once, and in one place, if necessary, and the contacts will always check that they're up to date.

Hopefully privacy mode would also turn on Tor as well.

Considering the "Bitcoin is anonymous" spin in the media, I really think we're going to have a lot of people unwittingly find themselves in a lot of trouble with criminals, spouses, friends, governments, etc. if they can't easily learn how Bitcoin is working for them in practice.  Somebody said here that users aren't stupid, but the client is making them stupid, and I completely agree.

Am I correct in thinking that if you keep A a secret between you and a friend, and agree to use some agreed upon sequence of serial numbers (could this just be trivial and the same for everyone?), that they could have access to an infinite number of your public keys that can't be associated by an outsider?  Edit: lol I think you just said this in the last sentence.

If so, then it seems like it could enable people to interface in the client with a contacts list instead of ugly addresses, but without having to reuse them or manually request new ones all the time.

I guess one major problem would be losing the master private key, and having people continue to send to addresses derived from the associated public key.

This could be mitigated by having your contact instead for each transaction get the master public key from an (untrusted) online storage server who stores it encrypted to your private key and your contact's public key, and check that it hasn't changed.  That way if you lose your wallet, you can stop everyone from sending to it in one step by deleting the master public keys from your storage server, and restart it again by uploading new ones for each of your contacts, without having to notify them, since their client can just start the agreed upon serial number sequence anew if they notice that the master public key has been changed.

Edit: Damn, I read your post two days ago, and forgot to re-read it before responding.  I apologize for basically restating what you did.

Was just about to say the same thing.

Edit: I think my questions were answered in this post http://forum.bitcoin.org/index.php?topic=28565.msg363945#msg363945

My curiosity won't stop nagging, so here's some bounties

Thanks for the link!

Please forgive all the parentheses in the following...

The first two problems you listed I think can be avoided by treating votes just like bitcoins, but having "election cycles" to compensate for their irretractablility.  For every election cycle (measured by some fixed number of blocks that is limited by the cost and time of running an election), every bitcoin address (or a uniquely determined address, so that bitcoin-containing private keys don't have to be network facing) is issued an equal number of "votecoins".  (Can actual blockchain-recorded transactions be avoided for this issuance?  Can it be done by an understanding that spends from the determined votecoin address up to the amount contained in the determining bitcoin address at the start of the election cycle are allowed during the the election cycle?)  During the rest of the election period, the network will accept votecoin transactions only for those issued during the current election cycle, until the end when some fixed number of addresses containing the most votecoins are elected to be the "representatives" during the next election cycle.

I'm not sure how resource intensive this search for the top votecoin containing addresses would be.

Perhaps voter participation could be incentivized using some portion of the transaction fees and newly issued bitcoins.  I'm reluctant to propose schemes to do this, though, since all the ones that I can think of don't really produce the right incentives, and also create perverse ones.  The larger bitcoin holders obviously have an interest in delegating their votes, but hopefully a really simple UX (vote delegation needs to be automated every election cycle according to user inputted delegates and weightings) and some peer pressure/annoying requests from the client/P. Diddy would be enough to motivate the rest.  Then again, maybe it won't matter if a bunch of the bitcoin-poor don't care enough to vote.

Notice that the public nature of the votecoin transaction history would help keep the delegates honest/effective.

Also note that storage requirements shouldn't be an issue since votecoin transactions from old election cycles don't need to be held on to.

Miners still seem to be necessary to keep time and bundle transactions, but the hashing power/reward they require could possibly be minimized the elected representatives' ability to regulate/make recommendations in the block selection process.

And if all the representatives are really doing is making recommendations to miners, then wouldn't only the miners have to be checking their signatures, usually?  This could allow for a much greater diversity of representatives, since the miners are already geared to accommodate higher overhead than clients.  I figure the only time the clients would need to check the signatures of the representatives is if the miners wanted to ignore the representatives en masse, creating a longer fork, and the clients wanted to ignore this longer fork.  But this might become too likely an attack vector if a significant amount of the overall hashing power of the miners is made obsolete by this system.

And if it's just recommendations, then would any of this require a separate blockchain/breaking change to the protocol?  Can the votecoin rules (their periodic creation and finite trading period) be accommodated somehow into the existing protocol?

Edit: From Mike, "There is a method of batch verifying ECDSA  signatures that's much faster than normal. It might change the economics of what you want to do: http://www.springerlink.com/content/h758580006764h26/ "

It sounds like it could scale to more than just a few.  And the voting power might flow much more easily away from corrupted players than with SWIFT due to the almost zero barriers to retracting votes, and to enter into the market to supplant the established delegates.  Remember, with delegated voting you don't necessarily give your vote directly to who will eventually cast it - you can just pass it on to someone you trust, hopefully solving the problem of rational ignorance/apathy.  That or the bad guys will just buy up all the votes  Or maybe the good guys will?

I guess the relevant question is if this would do a good enough job of decentralizing the "voting power" and making it accountable?  If so, the benefits listed above (that have survived) seem pretty significant.  It might at least be a good approach to smaller blockchains that don't expect to attract enough outside computing power to keep them secure.

That is good to hear!  I understand that proposals from people who obviously aren't qualified to program the shit they propose, not to mention that most of what they propose is indeed shit, probably gets pretty annoying.

Not at all!  I quite appreciate your thoughtful responses!

If there are relatively few delegates, and if they could each store their votes in single addresses, this could save a significant amount overhead for the network as a whole during voting/checking.

I suppose stakeholders by definition have an incentive to delegate their votes in such a way as to minimize the overhead in the network, but could this alone lead to some stable equilibrium?

Maybe you could also cull some necessary amount of the least influential addresses in the vote in order to help to reduce overhead to a workable amount?

I'm not sure if there's a transaction signing scheme to deal with retracted votes though, so I don't know if such a delegated voting scheme can even work.

Haha, I thought it felt a bit too obvious.  Well at least I have a greater, more justified, appreciation for Bitcoin now.

This whole thing actually came from thinking of a way to solve the checkpoint problem Ben Laurie wrote about.  If votes don't need to occur very often, then would the bandwidth/checking cost be such a big deal?  Is his issue even really a problem?

I think a hybrid approach would only allow stakeholders to sign whole blocks that have already been found.  And then miners could defer authority to the stakeholders when they do, and work forward from that block.  This would decrease the confirmation time to 10 minutes on average.  And it would remove the need for checkpoints, making Ben Laurie a happier camper.

I think a fork is more appropriate, since it incentivises the existing userbase to participate and avoids alienating them, and it solves the initial distribution problem, allowing for a very diverse voting group from the start.  I see Bitcoin as having made some progress at solving the social problems (bootstrapping a new currency) just as much as it has solved the technical ones.  No need to throw this progress away IMHO.

But Ben Laurie would be much happier

This alternative wouldn't need computing power - that's the point.

Furthermore, if you want more influence in the current system, all you have to do is buy yourself more computing resources.  Morally not much different than buying yourself more bitcoins AFAICT.

Lastly, if the bitcoin-rich (as opposed to the computing power-rich) started "voting" themselves more new bitcoins than the allowed amount, then people would lose confidence in the currency, and the bitcoin-rich would no longer be rich in any meaningful sense.  They have more incentive to maintain the currency's value than the current miners do, it seems.

Company shares sounds like a great application, too.  The proof-of-stake alternative seems like it could be a good way to prevent unwarranted outside influence from messing with smaller scale public ledgers like they can with proof-of-work.

This unwarranted outside influence also seems to be why alternative Bitcoin implementations don't seem feasible now - you need enough miners to be on board to secure the network against outside attackers, whereas attackers can only come from within using the proof-of-stake alternative.  All it needs is a sufficiently diverse userbase.

This is relevant to Bitcoin as an alternative means of forming consensus on the valid transaction history, or the public ledger at least.  But all it would necessarily borrow from Bitcoin is the public ledger contained in the block chain, in order to co-opt its userbase.

I've got an idea, and I'm wondering if it's been discussed/ripped apart here yet:

I'm wondering if as bitcoins become more widely distributed, whether a transition from a proof of work based system to a proof of stake one might happen.  What I mean by proof of stake is that instead of your "vote" on the accepted transaction history being weighted by the share of computing resources you bring to the network, it's weighted by the number of bitcoins you can prove you own, using your private keys.

For those that don't want to be actively verifying transactions, and so that not all private keys need to be facing the network, votes could be delegated to other addresses via some kind of nonstandard Bitcoin transaction.  In this way, voting power would accumulate with trusted delegates instead of miners.  New bitcoins and transaction fees could be randomly and periodically distributed to delgates, weighted by the number of votes they've accumulated, thereby incentivising diversity of the delegates and direct voters.

If the implementation could be done, it proved to maintain at least a similar level of privacy and trustworthiness, and it only minimally complicated the UX, I'm thinking that a proof of stake based fork could out-compete a proof of work one due to much lower transaction fees, since its network wouldn't need to support the cost of the miners' computing resources.  (Note that the vote delegation scheme has bandwith/storage overhead that would offset these savings by some amount which would hopefully be relatively small.)

Some other potential improvements this system could offer:

• Possibly quicker, more definite confirmation of transactions, depending on how it can be implemented.
  
• The "voting power" may be more trustworty, since it would accumulate in a bottom-up fashion via a network of trust, instead of in the somewhat arbitrary way it accumulates now.  (Note the potential problem of vote-buying here.)
• It would remove the physical point of failure of bitcoin mining equipment, which can be confiscated or made illegal to run.
• It could be used to provide stakeholders a means of making their voices heard (via the delegated voting system it establishes) when it comes to proposals for software updates and protocol changes.

Anyway, I just wanted to throw the idea out here to see if there are any obvious reasons why it couldn't be implemented, and to hopefully spark a discussion amongst those better qualified than me.

Cheers.

Wikileaks recently tweeted a reply (http://www.twitlonger.com/show/b8qli4) to a news article spreading FUD about Bitcoin.  In it they suggested Bitcoin "be augmented with a sub currency that has fixed time spend retractability if it is to be successful as a safe storage (as well as exchange) currency for the average person".

I was thinking the purposes of this could be accomplished by the client putting a fixed time delay on sends.  Of course, the user could always have the option to force transactions immediately.

If the recipient needs proof that the sender indeed has the necessary funds to send in the meantime, a message could be signed using the private key associated with an address containing them.

This would also provide some protection against "fat finger trades".

Am I understanding their concerns correctly?  Does this address them, effectively?

Edit: I guess part of their concern is theft.  Hopefully this can just be sufficiently mitigated by better security features in the client.

If you evaluated the cdf of a gamma distribution with parameters 7 and 1/10min at 10min to get 0.0000002, and 1 - the pdf of the binomial distribution with parameters 132000 and 0.0000002 evaluated at 0 to get 99.7%, then I think it's correct.  I'm too lazy to calculate it, though.

Also, http://www.xkcd.com/882/

I'm also fine with my donation going to this.

I can pledge 0.5 BTC for the refund thing if I end up getting my donation back.

+1
A federation of servers you don't have to trust is good enough.

This (OPEN-TRANSACTIONS): http://forum.bitcoin.org/index.php?topic=20425.0

If Bitcoin makes you giddy, then this should too.

It provides the technical groundwork for an entire financial industry done right.

And sign it with the private key associated with the address you donated from.  I think there's a patch that allows you to do this.

Allow this for a certain period of time before sending everything to the faucet.