[Cryptography] In the latest unexpected ransomware twist ...

[jrzx]

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Monday, June 21st, 2021 at 4:12 PM, Adam P. Goucher <apgoucher at gmx.com> wrote:
> if you have a transaction with three different inputs of 5
> BTC and three different outputs of 5 BTC, there is no way to
> define which input 'corresponds' to which output; doing
> so is meaningless. This is the basis of the CoinJoin
> privacy-enhancing technique

Coinjoin would work great if all outputs were restricted to a
few simple values, 0.1, 0.2, 0.5, 1, 2, 5, 10, etc.

Unfortunately on any blockchain with open entry, you have
to charge people to store data on the blockchain, and the
bitcoin blockchain takes the approach of charging people
by shaving transactions, so you cannot have an a transaction
with five inputs of 1, and five outputs of 1.

Which opens the sudoko attack on coinjoin.

coinjoin still works, but it is more difficult and
inconvenient to do it right than it needs to be, and
it still leaks more information that it should.

For a blockchain to properly support coinjoin, needs to
support some other method of charging people for storing data
on the blockchain.