Update spending policy post with review suggestions

diff --git a/content/blog/2021/spending_policy_demo.md b/content/blog/2021/spending_policy_demo.md
index 339cc19fdfab2ee4371647c0cc6811ed4d5c6df2..838e87b0a776721b6399d1458f44e99c800fe8df 100644 (file)
--- a/content/blog/2021/spending_policy_demo.md
+++ b/content/blog/2021/spending_policy_demo.md
@@ -19,9 +19,9 @@ The scenario we will simulate is a wallet with two spending policies:
 
 A. **three** out of **three** signers must sign spending transaction input [UTXO](https://developer.bitcoin.org/glossary.html)s, **OR** 
 
-B. **two** out of **three** signers must sign **AND** the input UTXOs must be in a block mined a set relative time before the block of the spending transaction
+B. **two** out of **three** signers must sign **AND** the input UTXOs must be a relative number of blocks older than the spending transaction's block
 
-In a real-world wallet a longer relative time-lock would probably be used, but we chose a short time-lock to make testing easier.
+In a real-world wallet a longer relative time-lock would probably be used, but we chose a two block time-lock to make testing easier.
 
 *Note: If you repeat these instructions on your own your extended keys, addresses, and other values will be different than shown in this post, but the end results should be the same.*
 
@@ -83,20 +83,18 @@ export CAROL_XPRV=$(cat carol-key.json | jq -r '.xprv')
 
 For this example we are using the [BIP-84](https://github.com/bitcoin/bips/blob/master/bip-0084.mediawiki) key path: `m/84h/1h/0h/0/*` to derive extended public keys to share with other wallet participants. 
 
-We also use the `sed` Unix command to remove the origin master key fingerprint and path from our xpub keys since those parts do not need to be shared between wallet participants.
-
 ```bash
-export ALICE_XPUB=$(bdk-cli key derive --xprv $ALICE_XPRV --path "m/84'/1'/0'/0" | jq -r ".xpub" | sed 's/^\[.*\]//g')
+export ALICE_XPUB=$(bdk-cli key derive --xprv $ALICE_XPRV --path "m/84'/1'/0'/0" | jq -r ".xpub")
 echo \"$ALICE_XPUB\"
-"tpubDCyRBuncqwyAjSNiw1GWLmwQsWyhgPMEBpx3ZNpnCwZwf3HXerspTpaneN81KRxkwj8vjqH9pNWEPgNhen7dfE212SHfxBBbsCywxQGxvvu/0/*"
+"[5adb4683/84'/1'/0']tpubDCyRBuncqwyAjSNiw1GWLmwQsWyhgPMEBpx3ZNpnCwZwf3HXerspTpaneN81KRxkwj8vjqH9pNWEPgNhen7dfE212SHfxBBbsCywxQGxvvu/0/*"
 
-export BOB_XPUB=$(bdk-cli key derive --xprv $BOB_XPRV --path "m/84'/1'/0'/0" | jq -r ".xpub" | sed 's/^\[.*\]//g')
+export BOB_XPUB=$(bdk-cli key derive --xprv $BOB_XPRV --path "m/84'/1'/0'/0" | jq -r ".xpub")
 echo \"$BOB_XPUB\"
-"tpubDDQcUeBH9JFtgZEsHZBhmRu8AuZ8ceJY1umnipPVEg1had2coGMCWdFBXNnZWKoCPic3EMgDZTdmkAVNoakwNZu2ESSW36rQvts6VXGx4bU/0/*"
+"[5fdec309/84'/1'/0']tpubDDQcUeBH9JFtgZEsHZBhmRu8AuZ8ceJY1umnipPVEg1had2coGMCWdFBXNnZWKoCPic3EMgDZTdmkAVNoakwNZu2ESSW36rQvts6VXGx4bU/0/*"
 
-export CAROL_XPUB=$(bdk-cli key derive --xprv $CAROL_XPRV --path "m/84'/1'/0'/0" | jq -r ".xpub" | sed 's/^\[.*\]//g')
+export CAROL_XPUB=$(bdk-cli key derive --xprv $CAROL_XPRV --path "m/84'/1'/0'/0" | jq -r ".xpub")
 echo \"$CAROL_XPUB\"
-"tpubDCdxmvzJ5QBjTN8oCjjyT2V58AyZvA1fkmCeZRC75QMoaHcVP2m45Bv3hmnR7ttAwkb2UNYyoXdHVt4gwBqRrJqLUU2JrM43HippxiWpHra/0/*"
+"[de41e56d/84'/1'/0']tpubDCdxmvzJ5QBjTN8oCjjyT2V58AyZvA1fkmCeZRC75QMoaHcVP2m45Bv3hmnR7ttAwkb2UNYyoXdHVt4gwBqRrJqLUU2JrM43HippxiWpHra/0/*"
 ```
 
 ### Step 4: Create wallet descriptors for each participant
@@ -109,7 +107,7 @@ To the [output descriptor](https://bitcoindevkit.org/descriptors/):
 
 `wsh(thresh(3,pk(Alice),s:pk(Bob),s:pk(Carol),sdv:older(2)))`
 
-This descriptor requires spending transaction inputs must be signed by all three signers, or by two signers ~17mins (512*2 seconds) after being included in a bitcoin block. 
+This descriptor requires spending transaction inputs must be signed by all three signers, or by two signers and the spent UTXOs must be older than two blocks. 
 
 Each participant's descriptor only uses their own XPRV key plus the XPUB keys of the other participants.
 
@@ -194,7 +192,7 @@ bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR policies
       "n": 4,
       "type": "PARTIAL"
     },
-    "id": "tjdhrksc",
+    "id": "ydtnup84",
     "items": [
       {
         "contribution": {
@@ -212,8 +210,8 @@ bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR policies
         "contribution": {
           "type": "NONE"
         },
-        "fingerprint": "4331a5e6",
-        "id": "w0xldflx",
+        "fingerprint": "5fdec309",
+        "id": "dzkmxcgu",
         "satisfaction": {
           "type": "NONE"
         },
@@ -223,8 +221,8 @@ bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR policies
         "contribution": {
           "type": "NONE"
         },
-        "fingerprint": "eebab672",
-        "id": "ghlsq5yk",
+        "fingerprint": "de41e56d",
+        "id": "ekfu5uaw",
         "satisfaction": {
           "type": "NONE"
         },
@@ -260,7 +258,7 @@ bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR policies
 The transaction can also be created by Alice, Bob, or Carol.
 
 ```bash
-bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"tjdhrksc\": [0,1,2]}"
+bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"ydtnup84\": [0,1,2]}"
 {
   "details": {
     "fees": 169,
@@ -274,7 +272,7 @@ bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27y
   "psbt": "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"
 }
 
-export ALICE_PSBT=$(bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"tjdhrksc\": [0,1,2]}" | jq -r ".psbt")
+export ALICE_PSBT=$(bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"ydtnup84\": [0,1,2]}" | jq -r ".psbt")
 ```
 
 ### Step 6a: Sign and finalize PSBTs
@@ -367,10 +365,13 @@ bdk-cli wallet -w bob -d $BOB_DESCRIPTOR get_balance
 
 ### Step 4b: Create spending transaction
 
-This spending transaction uses Alice and Bob's keys plus the ~17 minute (512x2 second) relative time-lock, see above [Step 4a](#step-4a-view-wallet-spending-policies) for the policy id. The transaction can be created by Alice or Bob.
+This spending transaction uses Alice and Bob's keys plus a two block relative time-lock, see above [Step 4a](#step-4a-view-wallet-spending-policies) for the policy id. The transaction can be created by Alice or Bob.
+
+A time based relative time-lock can be used instead of one based on blocks but is slightly more complicated to calculate. See 
+[BIP-68](https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki#specification) for the details.
 
 ```bash
-bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"tjdhrksc\": [0,1,3]}"
+bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"ydtnup84\": [0,1,3]}"
 {
   "details": {
     "fees": 169,
@@ -384,7 +385,7 @@ bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27y
   "psbt": "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"
 }
 
-export ALICE_PSBT2=$(bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"tjdhrksc\": [0,1,3]}" | jq -r ".psbt")
+export ALICE_PSBT2=$(bdk-cli wallet -w alice -d $ALICE_DESCRIPTOR create_tx -a --to tb1qm5tfegjevj27yvvna9elym9lnzcf0zraxgl8z2:0 --external_policy "{\"ydtnup84\": [0,1,3]}" | jq -r ".psbt")
 ```
 
 ### Step 5b: Sign and finalize PSBTs