docs(core): replace Purpose48 with BIP-48

https://github.com/bitcoin/bips/blob/master/bip-0048.mediawiki

core/.changelog.d/1744.changed

@@ -0,0 +1 @@
+Refer to `m/48'/...` multisig derivation paths as BIP-48 instead of Purpose48.

core/src/apps/bitcoin/keychain.py

@@ -35,11 +35,12 @@ if False:
 # BIP-45 for multisig: https://github.com/bitcoin/bips/blob/master/bip-0045.mediawiki
 PATTERN_BIP45 = "m/45'/[0-100]/change/address_index"
 
-# Electrum Purpose48. See docs/misc/purpose48.md
-# Electrum does not seem to use the raw script type, it is included here for completeness.
-PATTERN_PURPOSE48_RAW = "m/48'/coin_type'/account'/0'/change/address_index"
-PATTERN_PURPOSE48_P2SHSEGWIT = "m/48'/coin_type'/account'/1'/change/address_index"
-PATTERN_PURPOSE48_SEGWIT = "m/48'/coin_type'/account'/2'/change/address_index"
+# BIP-48 for multisig: https://github.com/bitcoin/bips/blob/master/bip-0048.mediawiki
+# The raw script type is not part of the BIP (and Electrum, as a notable implementation,
+# does not use it), it is included here for completeness.
+PATTERN_BIP48_RAW = "m/48'/coin_type'/account'/0'/change/address_index"
+PATTERN_BIP48_P2SHSEGWIT = "m/48'/coin_type'/account'/1'/change/address_index"
+PATTERN_BIP48_SEGWIT = "m/48'/coin_type'/account'/2'/change/address_index"
 
 # BIP-49 for segwit-in-P2SH: https://github.com/bitcoin/bips/blob/master/bip-0049.mediawiki
 PATTERN_BIP49 = "m/49'/coin_type'/account'/change/address_index"
@@ -97,7 +98,7 @@ def validate_path_against_script_type(
         script_type in (InputScriptType.SPENDADDRESS, InputScriptType.SPENDMULTISIG)
         and multisig
     ):
-        patterns.append(PATTERN_PURPOSE48_RAW)
+        patterns.append(PATTERN_BIP48_RAW)
         if coin.slip44 == SLIP44_BITCOIN or (
             coin.fork_id is not None and coin.slip44 != SLIP44_TESTNET
         ):
@@ -113,7 +114,7 @@ def validate_path_against_script_type(
     elif coin.segwit and script_type == InputScriptType.SPENDP2SHWITNESS:
         patterns.append(PATTERN_BIP49)
         if multisig:
-            patterns.append(PATTERN_PURPOSE48_P2SHSEGWIT)
+            patterns.append(PATTERN_BIP48_P2SHSEGWIT)
         if coin.slip44 == SLIP44_BITCOIN:
             patterns.append(PATTERN_GREENADDRESS_A)
             patterns.append(PATTERN_GREENADDRESS_B)
@@ -123,7 +124,7 @@ def validate_path_against_script_type(
     elif coin.segwit and script_type == InputScriptType.SPENDWITNESS:
         patterns.append(PATTERN_BIP84)
         if multisig:
-            patterns.append(PATTERN_PURPOSE48_SEGWIT)
+            patterns.append(PATTERN_BIP48_SEGWIT)
         if coin.slip44 == SLIP44_BITCOIN:
             patterns.append(PATTERN_GREENADDRESS_A)
             patterns.append(PATTERN_GREENADDRESS_B)
@@ -137,7 +138,7 @@ def get_schemas_for_coin(coin: coininfo.CoinInfo) -> Iterable[PathSchema]:
     # basic patterns
     patterns = [
         PATTERN_BIP44,
-        PATTERN_PURPOSE48_RAW,
+        PATTERN_BIP48_RAW,
     ]
 
     # patterns without coin_type field must be treated as if coin_type == 0
@@ -173,8 +174,8 @@ def get_schemas_for_coin(coin: coininfo.CoinInfo) -> Iterable[PathSchema]:
             (
                 PATTERN_BIP49,
                 PATTERN_BIP84,
-                PATTERN_PURPOSE48_P2SHSEGWIT,
-                PATTERN_PURPOSE48_SEGWIT,
+                PATTERN_BIP48_P2SHSEGWIT,
+                PATTERN_BIP48_SEGWIT,
             )
         )
 

docs/SUMMARY.md

@@ -43,7 +43,6 @@
   - [Generated Files](misc/generated-files.md)
   - [Git Hooks](misc/git-hooks.md)
   - [Monorepo Notes](misc/monorepo.md)
-  - [Purpose48 derivation scheme](misc/purpose48.md)
   - [Review Process](misc/review.md)
   - [Changelog](misc/changelog.md)
   - [TOIF Image Format](misc/toif.md)

docs/misc/purpose48.md

@@ -1,52 +0,0 @@
-# Purpose48 derivation scheme
-
-Per [BIP-43], the first level of the derivation path is used as a "purpose". The purpose
-number is usually selected to match the BIP number: e.g., BIP-49 uses purpose `49'`.
-
-There is no officially proposed **BIP-48** standard. Despite that, a de-facto standard
-for the purpose `48'` exists in the wild and is implemented by several HD wallets, most
-notably [Electrum]. This standard was never before formally
-specified, and this document aims to rectify the situation.
-
-## Motivation
-
-Purpose48 is intended for multisig scenarios. It allows using multiple script types from
-a single logical account or root key, while keeping multisig keys separate from
-single-sig keys.
-
-## Specification
-
-The following BIP-32 path levels are defined:
-
-```
-m / 48' / coin_type' / account' / script_type' / change / address_index
-```
-
-Meaning of all fields except `script_type` is defined in [BIP-44]
-
-`script_type` can have the following values:
-
-* `0`: raw [BIP-11] (p2ms) multisig
-* `1`: p2sh-wrapped segwit multisig (p2wsh-p2sh)
-* `2`: native segwit multisig (p2wsh)
-
-The path derivation is hardened up to and including the `script_type` field.
-
-## Trezor implementation
-
-`script_type` value `0` corresponds to `SPENDMULTISIG`/`PAYTOMULTISIG`.
-
-Value `1` corresponds to `SPENDP2SHWITNESS`/`PAYTOP2SHWITNESS`.
-
-Value `2` corresponds to `SPENDWITNESS`/`PAYTOWITNESS`.
-
-## References
-
-Electrum implementation: https://github.com/spesmilo/electrum/blob/9931df9f254e49eb929723be62af61971b3032c8/electrum/keystore.py#L862-L889
-
-Trezor implementation: TBD
-
-[Electrum]: https://electrum.org/
-[BIP-11]: https://github.com/bitcoin/bips/blob/master/bip-0011.mediawiki
-[BIP-43]: https://github.com/bitcoin/bips/blob/master/bip-0043.mediawiki
-[BIP-44]: https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki

tests/device_tests/test_msg_getaddress_show.py

@@ -92,7 +92,7 @@ def test_show_multisig_3(client):
         )
 
 
-VECTORS_MULTISIG = (  # script_type, purpose48_type, address, xpubs, ignore_xpub_magic
+VECTORS_MULTISIG = (  # script_type, bip48_type, address, xpubs, ignore_xpub_magic
     (
         messages.InputScriptType.SPENDMULTISIG,
         0,
@@ -165,15 +165,15 @@ VECTORS_MULTISIG = (  # script_type, purpose48_type, address, xpubs, ignore_xpub
 @pytest.mark.skip_t1
 @pytest.mark.multisig
 @pytest.mark.parametrize(
-    "script_type, purpose48_type, address, xpubs, ignore_xpub_magic", VECTORS_MULTISIG
+    "script_type, bip48_type, address, xpubs, ignore_xpub_magic", VECTORS_MULTISIG
 )
 def test_show_multisig_xpubs(
-    client, script_type, purpose48_type, address, xpubs, ignore_xpub_magic
+    client, script_type, bip48_type, address, xpubs, ignore_xpub_magic
 ):
     nodes = [
         btc.get_public_node(
             client,
-            tools.parse_path(f"48h/0h/{i}h/{purpose48_type}h"),
+            tools.parse_path(f"48h/0h/{i}h/{bip48_type}h"),
             coin_name="Bitcoin",
         )
         for i in range(3)
@@ -235,7 +235,7 @@ def test_show_multisig_xpubs(
             btc.get_address(
                 client,
                 "Bitcoin",
-                tools.parse_path(f"48h/0h/{i}h/{purpose48_type}h/0/0"),
+                tools.parse_path(f"48h/0h/{i}h/{bip48_type}h/0/0"),
                 show_display=True,
                 multisig=multisig,
                 script_type=script_type,