core/slip39: remove _encrypt

(cherry picked from commit 53ca61ab00)

core/src/trezor/crypto/slip39.py

@@ -208,20 +208,6 @@ def _get_salt(identifier: int) -> bytes:
     )
 
 
-def _encrypt(
-    master_secret: bytes, passphrase: bytes, iteration_exponent: int, identifier: int
-) -> bytes:
-    l = master_secret[: len(master_secret) // 2]
-    r = master_secret[len(master_secret) // 2 :]
-    salt = _get_salt(identifier)
-    for i in range(_ROUND_COUNT):
-        (l, r) = (
-            r,
-            xor(l, _round_function(i, passphrase, iteration_exponent, salt, r)),
-        )
-    return r + l
-
-
 def decrypt(
     identifier: int,
     iteration_exponent: int,

tests/device_tests/test_msg_resetdevice_shamir.py

@@ -152,14 +152,14 @@ class TestMsgResetDeviceT2(TrezorTest):
         assert resp.passphrase_protection is False
 
 
-def validate_mnemonics(mnemonics, threshold, expected_secret):
+def validate_mnemonics(mnemonics, threshold, expected_ems):
     # We expect these combinations to recreate the secret properly
     for test_group in combinations(mnemonics, threshold):
         # TODO: HOTFIX, we should fix this properly by modifying and unifying the python-shamir-mnemonic API
         ms = shamir.combine_mnemonics(test_group)
         identifier, iteration_exponent, _, _, _ = shamir._decode_mnemonics(test_group)
         ems = shamir._encrypt(ms, b"", iteration_exponent, identifier)
-        assert ems == expected_secret
+        assert ems == expected_ems
     # We expect these combinations to raise MnemonicError
     for test_group in combinations(mnemonics, threshold - 1):
         with pytest.raises(