diff --git a/docs/developer/api.md b/docs/developer/api.md
index f68ba67..51c9fb5 100644
--- a/docs/developer/api.md
+++ b/docs/developer/api.md
@@ -169,9 +169,14 @@ boundary; there is no legacy decoder.
 The one-shot function creates only unshared secrets:
 
 ```python
-generate_master_seed(seed_bytes=None, *, byte_length=None, identifier=None)
+generate_master_seed(seed_bytes=None, *, byte_length=None, identifier=None, fingerprint=None)
 ```
 
+A fresh seed with no `identifier` needs `fingerprint`: a callable that takes
+the seed bytes and returns their four-byte BIP32 master fingerprint. This
+package has no secp256k1 arithmetic, so the CLI asks Bitcoin Core. Without
+either argument, fresh generation raises `ValueError`.
+
 Shared creation uses `CreationCeremony.master_seed(...)` or
 `CreationCeremony.from_secret(...)`. Exactly one of `share_count` and `indices`
 is required. `next_share()` returns one pending share, `confirm(text)` must
diff --git a/src/codex32/bech32.py b/src/codex32/bech32.py
index 59befc7..7704f01 100644
--- a/src/codex32/bech32.py
+++ b/src/codex32/bech32.py
@@ -1,3 +1,28 @@
+# Portions of this file are derived from work by:
+#   Copyright (c) 2017, 2020 Pieter Wuille
+#   Source: https://github.com/sipa/bech32/blob/master/ref/python/segwit_addr.py
+#
+# Additional code and modifications:
+#   Copyright (c) 2026 Ben Westgate <benwestgate@protonmail.com>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
 """Bech32 character, container, and bit-conversion helpers."""
 
 from codex32.checksums import _Checksum
diff --git a/src/codex32/checksums.py b/src/codex32/checksums.py
index 95bf742..6061d1e 100644
--- a/src/codex32/checksums.py
+++ b/src/codex32/checksums.py
@@ -1,3 +1,32 @@
+# The polymod arithmetic in this file is derived from work by:
+#   Copyright (c) 2017, 2020 Pieter Wuille, MIT License
+#   Source: https://github.com/sipa/bech32/blob/master/ref/python/segwit_addr.py
+# codex32 constants in this file are derived from work by:
+#   Author: Leon Olsson Curr and Pearlwort Sneed <pearlwort@wpsoftware.net>
+#   License: BSD-3-Clause
+#   Source: https://github.com/bitcoin/bips/blob/master/bip-0093.mediawiki
+#
+# Additional code:
+# Copyright (c) 2026 Ben Westgate <benwestgate@protonmail.com>, MIT License
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
 """Immutable checksum specifications used by codex32."""
 
 from dataclasses import dataclass