add "A private flow through JoinMarket" guide

joinmarket/joinmarket_private_flow.md

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+# A private flow through JoinMarket
+
+Guidance to get started with sending bitcoin through the JoinMarket wallet following basic good practices.
+
+## Common definitions
+### Mixdepth
+* one of the accounts in the joinmarket wallet
+* abbreviated to m0 / m1 / m2 / m3 / m4
+* all are derived from the same BIP32 compatible HD seed
+
+### Sweep
+* sending one or multiple utxos without creating change.
+* can be achieved by sending all utxos from a mixdepth or freezing any which should be sent.
+* the amount is not fixed and fees come of the sum of the inputs.
+
+### Status labels
+* applied automatically by JoinMarket via a simple transaction analyses
+
+#### `deposit`: output of a simple transaction to new address
+#### `cj-out`: one of the equal amount outputs
+#### `change-out`: one of the unique amount outputs from a cj
+#### `non-cj-change`: output of a transaction without equal amounts
+#### `reused`: a utxo on an address which has been used previously
+
+### Orderbook
+* Any platform collecting the public orders of the peers
+* General docs on the order book (including how to run without Bitcoin Core): https://github.com/JoinMarket-Org/joinmarket-clientserver/blob/master/docs/orderbook.md
+* a public example: <https://nixbitcoin.org/orderbook>
+### Minimum size to coinjoin
+* the default is 100k sats (+/-10%) so that is a safe choice.
+* on the example below offers start at 6 peers offering min 27300 sats.
+
+### Maximum size to coinjoin
+* the max amount offered is limited by the wallet of each Maker
+* it is the highest amount in one single mixdepth (-0-10%)
+* multiple bitcoin amounts are offered by several (10+) peers
+* on the example below 21 peers offer 19+ BTC
+### Screenshots taken from <https://nixbitcoin.org/orderbook> in March 2022.
+* Click the top of the line to order by it's attribute
+<p align="left">
+  <img width="147" src="../images/joinmarket_minsize.png">
+  <img width="100">
+  <img width="150"  src="../images/joinmarket_maxsize.png">
+</p>
+
+## The flow of funds
+
+Guidance is provided in the behaviour of the Tumbler script which could be used for the quickest result.
+Discussed in:
+* https://gist.github.com/chris-belcher/7e92810f07328fdfdef2ce444aad0968
+* https://github.com/JoinMarket-Org/joinmarket-clientserver/blob/master/docs/tumblerguide.md
+* https://joinmarket.me/blog/blog/the-445-btc-gridchain-case/
+
+### Deposit
+* send to m0 - could be any of the accounts, but selected the first for simplicity
+* deposit a single or multiple coins from a single funding source at a time
+* select the newly deposited coin(s) with freeze/unfreeze if there are others in the account
+
+### Sweep
+* start with detaching the deposited coins from their history
+* can send to the same account (could be any, but keep it simple)
+* there is no change created, so there is need to separate the `cj-out` from the `change-out`
+
+### Send or participate in multiple coinjoins
+* alternate being a Taker and a Maker for the best results
+* stretch out in time
+* the Taker acts as the coinjoin coordinator
+    * has the most privacy benefits
+    * pays the fees (miner and coinjoin fees)
+
+#### The Taker role
+* send coinjoins to the next mixdepth (acting as a Taker)
+* when sending can merge multiple coins in the coinjoin by sending custom amounts or sweeping
+
+#### The Maker role
+* activate the Yield Generator (Maker / Earn)
+* to get selected more often it is best to have a a sizeable Fidelity Bond. See:
+    * https://nixbitcoin.org/orderbook/fidelitybonds
+    * https://github.com/JoinMarket-Org/joinmarket-clientserver/blob/master/docs/fidelity-bonds.md
+* as a Maker the coins will circle through the accounts automatically:  
+... m0 -> m1 -> m2 -> m3 -> m4 -> m0 -> m1 -> m2 -> m3 -> m4 ...
+* only the `cj-out`  propagates to the next account
+* the `change-out` stays behind in the same acount where the funding utxo was
+
+### Leaving the JoinMarket wallet
+
+* the more coinjoins the coins were through the better
+* consider that the privacy benefit from coinjoins breaks down with time as the peers are gradually exposed or clustered
+* if deposited only to m0 and followed the steps above all coins in m4 must have been through at least 5 coinjoins
+* in a long running, active Maker wallet some funds could have made multiple circles - there is no indication of this by default
+* can only send (merge coins) from one account at a time
+* leave to multiple separate destinations (separate wallets with different purposes - not to be merged later)
+* avoid sending out the whole amount which entered the wallet a few transactions ago all at once
+* pay with Payjoin to BIP78 compatible wallets to obfuscate the amount sent <https://en.bitcoin.it/wiki/PayJoin_adoption>
+* fund lightning nodes or send to cold storage with a coinjoin
+  * best is to sweep whole accounts or coins and not leave change behind
+  * don't merge a change from a previous transactions when sending to a new destinations
+
+## More Reading
+* https://github.com/JoinMarket-Org/joinmarket-clientserver/tree/master/docs
+* https://en.bitcoin.it/Privacy
+
+## Questions and discussions:
+* IRC through Matrix: https://matrix.to/#/#joinmarket:libera.chat
+* Telegram: https://t.me/joinmarket.org