move bip39 function

diff --git a/src/rust/bitbox02-rust-c/src/bip39.rs b/src/rust/bitbox02-rust-c/src/bip39.rs
index 6ea9fcd..f6e5db7 100644
--- a/src/rust/bitbox02-rust-c/src/bip39.rs
+++ b/src/rust/bitbox02-rust-c/src/bip39.rs
@@ -34,7 +34,7 @@ pub unsafe extern "C" fn rust_derive_bip39_seed(
 
 #[no_mangle]
 pub extern "C" fn rust_get_bip39_word(idx: u16, mut out: crate::util::BytesMut) -> bool {
-    let word = match bitbox02::keystore::get_bip39_word(idx) {
+    let word = match bitbox02_rust::bip39::get_word(idx) {
         Err(()) => return false,
         Ok(w) => w,
     };
diff --git a/src/rust/bitbox02-rust/src/bip39.rs b/src/rust/bitbox02-rust/src/bip39.rs
new file mode 100644
index 0000000..848c037
--- /dev/null
+++ b/src/rust/bitbox02-rust/src/bip39.rs
@@ -0,0 +1,40 @@
+// Copyright 2025 Shift Crypto AG
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use alloc::string::{String, ToString};
+
+/// `idx` must be smaller than BIP39_WORDLIST_LEN.
+pub fn get_word(idx: u16) -> Result<zeroize::Zeroizing<String>, ()> {
+    Ok(zeroize::Zeroizing::new(
+        bip39::Language::English
+            .word_list()
+            .get(idx as usize)
+            .ok_or(())?
+            .to_string(),
+    ))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_word() {
+        assert!(get_word(2048).is_err());
+
+        assert_eq!(get_word(0).unwrap().as_ref() as &str, "abandon");
+        assert_eq!(get_word(2047).unwrap().as_ref() as &str, "zoo");
+        assert_eq!(get_word(563).unwrap().as_ref() as &str, "edit");
+    }
+}
diff --git a/src/rust/bitbox02-rust/src/lib.rs b/src/rust/bitbox02-rust/src/lib.rs
index a8df3de..f7931b9 100644
--- a/src/rust/bitbox02-rust/src/lib.rs
+++ b/src/rust/bitbox02-rust/src/lib.rs
@@ -31,6 +31,7 @@ pub mod attestation;
 pub mod backup;
 pub mod bb02_async;
 mod bip32;
+pub mod bip39;
 pub mod hal;
 mod hash;
 pub mod hww;
diff --git a/src/rust/bitbox02-rust/src/workflow/mnemonic.rs b/src/rust/bitbox02-rust/src/workflow/mnemonic.rs
index 6d02d25..24e82da 100644
--- a/src/rust/bitbox02-rust/src/workflow/mnemonic.rs
+++ b/src/rust/bitbox02-rust/src/workflow/mnemonic.rs
@@ -60,7 +60,7 @@ fn create_random_unique_words(word: &str, length: u8) -> (u8, Vec<zeroize::Zeroi
                 if picked_indices.contains(&idx) {
                     continue;
                 };
-                let random_word = bitbox02::keystore::get_bip39_word(idx).unwrap();
+                let random_word = crate::bip39::get_word(idx).unwrap();
                 if random_word.as_str() == word {
                     continue;
                 }
@@ -172,7 +172,7 @@ fn lastword_choices(entered_words: &[&str]) -> Vec<u16> {
             let mnemonic = zeroize::Zeroizing::new(format!(
                 "{} {}",
                 entered_words.join(" "),
-                bitbox02::keystore::get_bip39_word(i).unwrap().as_str(),
+                crate::bip39::get_word(i).unwrap().as_str(),
             ));
             if let Ok(seed) = bitbox02::keystore::bip39_mnemonic_to_seed(&mnemonic) {
                 break seed;
@@ -205,7 +205,7 @@ fn lastword_choices(entered_words: &[&str]) -> Vec<u16> {
 fn lastword_choices_strings(entered_words: &[&str]) -> Vec<zeroize::Zeroizing<String>> {
     lastword_choices(entered_words)
         .into_iter()
-        .map(|word_idx| bitbox02::keystore::get_bip39_word(word_idx).unwrap())
+        .map(|word_idx| crate::bip39::get_word(word_idx).unwrap())
         .collect()
 }
 
diff --git a/src/rust/bitbox02/src/keystore.rs b/src/rust/bitbox02/src/keystore.rs
index 1dcfaa0..b8f4f4b 100644
--- a/src/rust/bitbox02/src/keystore.rs
+++ b/src/rust/bitbox02/src/keystore.rs
@@ -136,17 +136,6 @@ pub fn bip39_mnemonic_from_seed(seed: &[u8]) -> Result<zeroize::Zeroizing<String
     Ok(zeroize::Zeroizing::new(mnemonic.to_string()))
 }
 
-/// `idx` must be smaller than BIP39_WORDLIST_LEN.
-pub fn get_bip39_word(idx: u16) -> Result<zeroize::Zeroizing<String>, ()> {
-    Ok(zeroize::Zeroizing::new(
-        bip39::Language::English
-            .word_list()
-            .get(idx as usize)
-            .ok_or(())?
-            .to_string(),
-    ))
-}
-
 pub struct SignResult {
     pub signature: [u8; 64],
     pub recid: u8,
@@ -428,15 +417,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn test_get_bip39_word() {
-        assert!(get_bip39_word(2048).is_err());
-
-        assert_eq!(get_bip39_word(0).unwrap().as_ref() as &str, "abandon");
-        assert_eq!(get_bip39_word(2047).unwrap().as_ref() as &str, "zoo");
-        assert_eq!(get_bip39_word(563).unwrap().as_ref() as &str, "edit");
-    }
-
     #[test]
     fn test_get_ed25519_seed() {
         // No seed on a locked keystore.