docs(addressing): expand output descriptor

Author: johnsBeharry

addressing/output-descriptors.md

@@ -1,6 +1,21 @@
 # Output Descriptors
 
-## Part 1: Derivation Paths
+At first you would generate a private key for each wallet you owned. It's already difficult to store 1 private key safely so a big UX improvement came about with BIP32.
+
+> HD wallets which can be shared partially or entirely with different systems, each with or without the ability to spend coins[^3]
+
+## Why Output Descriptors?
+
+- [ ] [focus on xpub output descriptors, *e.g. from hardware wallets*]
+- [ ] Introduction to bip32
+- [ ] BIP44 derivation paths
+- [ ] BIP49 derivation paths
+- [ ] BIP84 derivation paths
+- [ ] Obtaining an xpub
+
+## Diving in
+
+### Part 1: Derivation Paths
 
 ```
 m / purpose' / coin_type' / account' / change / index
@@ -15,5 +30,20 @@ m / purpose' / coin_type' / account' / change / index
 - `0` - **Normal Child** (index `0`)
 - `0'` - **Hardened Child** (index / starts at `2147483648`)
 
-[1]: https://learnmeabitcoin.com/technical/derivation-paths	"Derivation Paths, How HD wallets derive keys."
+### Part X: Obtaining an xpub
+
+- https://github.com/bitcoin-core/HWI/blob/master/docs/examples.md
+
+## Risks of Sharing
+
+Do **NOT** share an xprv.
+
+Sharing an xpub...
+
+> If, and only if, the recipient *also* obtains a single private key from your wallet, the recipient can obtain all your private keys and steal your funds, just as if they had your xprv key.[^4]
+
+[^1]: https://learnmeabitcoin.com/technical/derivation-paths	"Derivation Paths, How HD wallets derive keys."
 
+[^2]: https://bitcoin.stackexchange.com/a/95595 "Deconstructed utxo output descriptor"
+[^3]: https://en.bitcoin.it/wiki/BIP_0032 "BIP32"
+[^4]: https://en.bitcoin.it/wiki/Deterministic_wallet_tools#Risks_of_Sharing_an_Extended_Public_Key_.28xpub.29