著者: Michael English 日付: To: tails-dev 題目: Re: [Tails-dev] Set coin selection to "privacy" by default in
Electrum
S7r, > Hello intrigeri, Michael,
>
> intrigeri wrote:
>> Hi Michael,
>>
>> Michael English:
>>> It also helps to reduce blockchain UTXO (unspent transaction
>>> outputs) bloat,
>> This makes me curious. How does this help with that property, exactly?
>> My intuition tells me that by restricting the set of coins that can be
>> spent to one single address, on the contrary, the software has fewer
>> possibilities to optimize towards 1. reusing existing unspent outputs;
>> and thus 2. avoiding to create more.
>>
>> Also: where was this text quoted from?
>>
> The text was copied from Electrum man page. The privacy coin chooser
> will not offer 100% anonymity, because that's technically not possible
> in a system using a public blockchain, but it will obfuscate information
> about sender's total BTC holdings so it's a plus. Yes, I was relating this to routing the SPV validation through Tor which
also obscures the addresses that a particular person owns. Without Tor,
the bloom filters that SPV wallets like Electrum use are not very
private at all. > UTXO's are basically the coins you can spend. The spendable coins are in
> UTXO's, not in addresses. Addresses are just a smart crypto way to let
> the world know in advance who has the right to spend a given UTXO. Good explanation. > Existing unspent outputs cannot be reused, they are burned and re-crated
> entirely every time. So you cannot spend part of a UTXO, you spend it
> all (practice does not recommend re-using addresses - it's true nothing
> keeps you from receiving the change in the same initial address that you
> spent from, but you'll have a different UTXO). Yes, when a transaction is created, all of the inputs must be spent in
their entirety. Whatever coins do not need to be sent to another person
are sent back to a "change address" which is a new address under the
control of the spender. If there are still coins left after the
destination address(es) and the change address(es), then it is
interpreted as a transaction fee for the miners to collect. >>> Routing transaction relay through Tor is only part of the solution. The blockchain is
>>> a public ledger that can be analyzed anytime after the initial transaction broadcast.
>>> Private coin selection impedes correlation of transaction inputs and outputs that
>>> could link back to an identity.
>> Sure. I hope our doc clearly states that it's very hard to use Bitcoin
>> in a privacy-preserving way, for some various value of "privacy".
>>
> Agreed, but the setting indicated by Michael could be shipped as a
> default imho. It makes sense in a context like Tails/Tor threat model.
> Yes, that is exactly my rational. Private coin selection is perfectly
suited to the context of Tails. I like to think of it as similar to
browser fingerprints in the Tor Browser. Onion routing and private coin
selection reduces the "bitcoin fingerprint" left by Tails users.