BIP85: Add Codex32 as application 93'

bip-0085.mediawiki

@@ -225,6 +225,129 @@ OUTPUT:
 * DERIVED ENTROPY=ae131e2312cdc61331542efe0d1077bac5ea803adf24b313a4f0e48e9c51f37f
 * DERIVED BIP39 MNEMONIC=puppy ocean match cereal symbol another shed magic wrap hammer bulb intact gadget divorce twin tonight reason outdoor destroy simple truth cigar social volcano
 
+===BIP93 (codex32)===
+Application Number: 93'
+
+The derivation path format is: <code>m/83696968'/93'/{header}'/{byte_len}'/{index}'</code> 
+
+Truncate trailing (least significant) bytes of the entropy after <code>byte_len</code>.
+
+Use this application to generate fresh codex32 strings (as defined in BIP-0093) for backups of BIP-0032 HD master seeds. Each codex32 string encodes a share or secret with a human-readable prefix, and a data part consisting of a threshold, identifier, share index, payload, and checksum.
+
+The header is concatenated to fit in one hardened index, as follows:
+* 8-digits: human-readable prefix code
+* 1-digit: threshold parameter (2 through 9, or 0)
+* 1-digit: share index (index from "sacdefghjk")
+
+Human-readable Prefix Table
+
+{|
+!hrp
+!Code
+|-
+| "ms"
+| 0
+|-
+| "cl"
+| 1
+|-
+|}
+
+Bytes Length Table
+
+{|
+! Bytes
+! Data Length (Characters)
+!Code
+|-
+| 16
+| 45
+| 16'
+|-
+| 32
+| 71
+| 32'
+|-
+| 64
+| 124
+| 64'
+|}
+Note: Other lengths between 16 and 64 are valid but not recommended, using corresponding hardened indices.
+
+Example of derivation path computation:
+
+<source lang="python">
+
+CANONICAL_INDICES = "sacdefghjk"
+VALID_HRP = {
+    "ms": 0,
+    "cl": 1
+}
+
+def bip93_parameters_to_path(hrp, threshold=0, identifier="", share_idx, byte_len, index=0):
+    if share_idx == "s":
+        threshold = 0
+    elif threshold < max(CANONICAL_INDICES.index(share_idx), 2):
+        raise InvalidShareIndex()
+    elif identifier:
+        index = int.from_bytes(bech32_decode(identifier), 'big') + index << 20
+    else:
+        raise MissingIdentifier()
+    header_path_int = (
+                        VALID_HRP[hrp] * 100 
+                        + threshold * 10
+                        + CANONICAL_INDICES.index(share_idx)
+                      )
+    return f"m/83696968'/93'/{header_path_int}'/{byte_len}'/{index}'"
+</source>
+
+Example: a codex32 secret with <code>hrp = "ms"</code>, <code>share_idx = "s"</code>, <code>byte_len = 16</code> would have the path <code>m/83696968'/93'/0'/16'/0'</code>, the next secret would be <code>m/83696968'/93'/0'/16'/1'</code> etc.
+
+For <code>byte_len % 5 > 0</code>, the truncated bytes from the entropy MUST be padded to a multiple of 5 bits. The <code>pad_len = 5 - byte_len * 8 % 5</code> padding bits are generated using CRC polynomial <code>(1 << pad_len) | 3</code> with an initial value of <code>0</code> and appended to the entropy bytes.
+
+====Unshared Secret====
+
+When <code>share_idx == "s"</code>, the output is a codex32 secret. The payload in a codex32 secret is a direct encoding of a BIP-0032 HD master seed. The threshold parameter and 4 character identifier are ignored for derivation and the value <code>threshold = 0</code> is used. If not specified, the threshold parameter SHOULD default to "0". The identifier SHOULD default to the 4 left-most characters of the Bech32-encoded BIP-0032 fingerprint derived from the master seed.
+
+Generate a 16-byte "ms" prefixed codex32 secret
+
+INPUT:
+* MASTER BIP32 ROOT KEY: xprv9s21ZrQH143K2LBWUUQRFXhucrQqBpKdRRxNVq2zBqsx8HVqFk2uYo8kmbaLLHRdqtQpUm98uKfu3vca1LqdGhUtyoFnCNkfmXRyPXLjbKb
+* PATH: m/83696968'/93'/0'/16'/0'
+
+OUTPUT:
+* DERIVED ENTROPY=
+* DERIVED CODEX32 SECRET=ms10xxxxs...
+
+Generate a 32-byte "cl" prefixed Core Lightning HSM secret with threshold parameter "2" and identifier "c00l"
+
+INPUT:
+* MASTER BIP32 ROOT KEY: xprv9s21ZrQH143K2LBWUUQRFXhucrQqBpKdRRxNVq2zBqsx8HVqFk2uYo8kmbaLLHRdqtQpUm98uKfu3vca1LqdGhUtyoFnCNkfmXRyPXLjbKb
+* PATH: m/83696968'/93'/100'/32'/0'
+
+OUTPUT:
+* DERIVED ENTROPY=
+* DERIVED CODEX32 SECRET=cl12c00ls...
+
+====Share Generation====
+
+When <code>share_idx != "s"</code>, the output is a codex32 share. Here the threshold and identifier MUST be specified as both impact derivation. The threshold parameter also restricts which <code>share_idx</code> values are valid. Only the first threshold indicies in alphabetical order may be generated. E.g.: For <code>threshold = 3</code>, shares <code>"a"</code>, <code>"c"</code>, and <code>"d"</code>.
+
+The index derivation level is serialized to include the chosen <code>identifier</code>, as follows:
+* 11-bits: bip85 index
+* 20-bits: 4 bech32 character identifier converted using the character table from BIP-0173
+Users should enter a unique <code>identifier</code> instead of incrementing <code>{index}</code> as different share sets SHOULD have unique identifiers.
+
+Generate a 16-byte <code>threshold = 3</code> codex32 share "A" with <code>identifier = "c00l"</code>
+
+INPUT:
+* MASTER BIP32 ROOT KEY: xprv9s21ZrQH143K2LBWUUQRFXhucrQqBpKdRRxNVq2zBqsx8HVqFk2uYo8kmbaLLHRdqtQpUm98uKfu3vca1LqdGhUtyoFnCNkfmXRyPXLjbKb
+* PATH: m/83696968'/93'/31'/16'/802303'
+
+OUTPUT:
+* DERIVED ENTROPY=
+* DERIVED CODEX32 SHARE A=ms13c00la...
+
 ===HD-Seed WIF===
 Application number: 2'
 
@@ -429,11 +552,11 @@ OUTPUT
 
 This specification is not backwards compatible with any other existing specification.
 
-This specification relies on BIP32 but is agnostic to how the BIP32 root key is derived. As such, this standard is able to derive wallets with initialization schemes like BIP39 or Electrum wallet style mnemonics.
+This specification relies on BIP32 but is agnostic to how the BIP32 root key is derived. As such, this standard is able to derive wallets with initialization schemes like BIP39, codex32 or Electrum wallet style mnemonics.
 
 ==References==
 
-BIP32, BIP39
+BIP32, BIP39, BIP93
 
 ==Reference Implementations==
 
@@ -443,6 +566,12 @@ BIP32, BIP39
 
 ==Changelog==
 
+===2.1.0 (2025-10-19)===
+
+====Added====
+
+* Codex32 application 93'
+
 ===2.0.0 (2025-09-19)===
 
 ====Fixed====