Add high level description

md/partially-blind-swap.md

@@ -18,6 +18,34 @@ signature](https://blog.cryptographyengineering.com/a-note-on-blind-signature-sc
 of Alice over a transaction spending the funding transaction without knowing `t`
 (similar to [Discreet Log Contracts](https://adiabat.github.io/dlc.pdf)).
 
+High level description
+---
+There is Alice as a central tumbler server who has many utxos, and many users
+(Bob and Charlie) with their individual utxos. The two parties can swap coins,
+so that the user knows the coins of the tumbler, but the tumbler cannot link
+the pre to post swap coins of the users, with the anonymity set of all users
+between the time of funding and retreaval. An outside observer only sees
+regular public key and signatures and no onchain scripts, all is "hidden"
+within these scriptless scripts public keys and signatures, so it is unclear
+that these transactions are actually a swap.
+
+   * User and tumbler communicate to generate a musig public key with the 
+     individual keys of tumbler and user, and the users asks the tumbler to 
+     fund this output O1.
+   * They generates another musig and the user funds this output O2.
+   * They pre-sign timelocked refund transactions before funding the musigs, in
+     the case either party goes offline.
+   * User has nonce commitment R and public key P of the tumbler coin O1, and 
+     with this he can calculates the sum [(blinded spending signature O1) * G],
+     with this he can set up an adaptor signature so that the tumbler needs to
+     reveal the blinded spending signature (the adaptor secret).
+   * Now the user gives his contribution to spending O2, and the tumbler can
+     claim O2 only when providing his full real signature and publishing this
+     on-chain which reveals the adaptor secret (the blinded spending signature).
+   * The user can now unblinding the adaptor secret spending signature (revealed
+     by the tumbler claiming O2) and he can combine this with his own signature
+     to spend O1.
+
 Protocol description
 ---
 Assume Alice has a permanent public key `A = a*G`, ephemeral pubkey `A1 = A +