feat: nut19 in nut20

20.md

@@ -2,6 +2,8 @@
 
 `optional`
 
+`depends on: NUT-19`
+
 ---
 
 Similar to [NUT-04][04], which covers minting via BOLT11 invoices, minting via [BOLT12](https://github.com/lightning/bolts/blob/master/12-offer-encoding.md) is also a two-step process: requesting a mint quote and minting tokens. This document describes both steps, focusing on BOLT12-specific considerations.
@@ -22,11 +24,17 @@ The wallet of `Alice` includes the following `PostMintQuoteBolt12Request` data i
   "unit": <str_enum["sat"]>,
   "description": <str|null>,
   "expiry": <int|null>,
-  "single_use": <bool>
+  "single_use": <bool>,
+  "pubkey": <str>
 }
 ```
 
-The `amount` field is optional and specifies the amount to mint. The `unit` field is mandatory. An optional `description` can be passed if the mint signals support for it in `MintMethodSetting`. If `single_use` is false, the offer can be paid multiple times. The optional `expiry` field specifies the unix timestamp when the offer expires it **MUST** be before the `max_expiry` in the `MintMethodSettings` if one is given.
+The `amount` field is optional and specifies the amount to mint. The `unit` field is mandatory. An optional `description` can be passed if the mint signals support for it in `MintMethodSetting`. If `single_use` is false, the offer can be paid multiple times. The optional `expiry` field specifies the unix timestamp when the offer expires it **MUST** be before the `max_expiry` in the `MintMethodSettings` if one is given. `pubkey` is the public key that will be required for signature verification during the minting process. The mint will only mint ecash after receiving a valid signature from the corresponding private key in the `PostMintRequest`. 
+
+> **Note:** While a pubkey is optinal as per [NUT-19][19] for [NUT-04][04] it is required in this NUT and the mint **MUST NOT** issue a mint quote if one is not included. 
+
+
+> **Privacy:** To prevent linking multiple mint quotes together, wallets **SHOULD** generate a unique public key for each mint quote request
 
 The mint `Bob` then responds with a `PostMintQuoteBolt12Response`:
 
@@ -36,7 +44,8 @@ The mint `Bob` then responds with a `PostMintQuoteBolt12Response`:
   "request": <str>,
   "expiry": <int>,
   "amount_paid": <int>,
-  "amount_issued": <int>
+  "amount_issued": <int>,
+  "pubkey": <str>
 }
 ```
 
@@ -60,7 +69,8 @@ Response of `Bob`:
   "request": "lno1qcp...",
   "expiry": 1701704757,
   "amount_paid": 0,
-  "amount_issued": 0
+  "amount_issued": 0,
+  "pubkey": "03d56ce4e446a85bbdaa547b4ec2b073d40ff802831352b8272b7dd7a4de5a7cac"
 }
 ```
 
@@ -82,6 +92,11 @@ Example request of `Alice` with curl:
 curl -X GET http://localhost:3338/v1/mint/quote/bolt12/DSGLX9kevM...
 ```
 
+#### Witness
+
+In order to mint ecash the wallet **MUST** include a signature as defined in [NUT-19][19].
+
+
 # Minting tokens
 
 After requesting a mint quote and paying the request, the wallet proceeds with minting new tokens by calling `POST /v1/mint/bolt12`.
@@ -95,11 +110,12 @@ The wallet `Alice` includes the following `PostMintBolt12Request` data in its re
 ```json
 {
   "quote": <str>,
-  "outputs": <Array[BlindedMessage]>
+  "outputs": <Array[BlindedMessage]>,
+  "witness": <str>
 }
 ```
 
-The `quote` is the quote ID from the previous step and `outputs` are `BlindedMessages` (see [NUT-00][00]) that the wallet requests signatures on. The sum of the outputs must equal the amount that can be minted (`amount_paid` - `amount_issued`).
+The `quote` is the quote ID from the previous step and `outputs` are `BlindedMessages` (see [NUT-00][00]) that the wallet requests signatures on. The sum of the outputs must equal the amount that can be minted (`amount_paid` - `amount_issued`). `witness` is the signature on the mint quote id as defined above.
 
 The mint `Bob` then responds with a `PostMintBolt12Response`:
 
@@ -175,3 +191,4 @@ Example `MintMethodSetting`:
 [10]: 10.md
 [11]: 11.md
 [12]: 12.md
+[19]: 19.md