diff --git a/tests/standard/fido2/extensions/test_hmac_secret.py b/tests/standard/fido2/extensions/test_hmac_secret.py
new file mode 100644
index 0000000..1d55b13
--- /dev/null
+++ b/tests/standard/fido2/extensions/test_hmac_secret.py
@@ -0,0 +1,168 @@
+import pytest
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+from fido2.utils import sha256, hmac_sha256
+from fido2.ctap import CtapError
+
+from tests.utils import FidoRequest, verify, shannon_entropy
+
+
+def get_salt_params(cipher, shared_secret, salts):
+    enc = cipher.encryptor()
+    salt_enc = b""
+    for salt in salts:
+        salt_enc += enc.update(salt)
+    salt_enc += enc.finalize()
+
+    salt_auth = hmac_sha256(shared_secret, salt_enc)[:16]
+    return salt_enc, salt_auth
+
+
+salt1 = b"\xa5" * 32
+salt2 = b"\x96" * 32
+salt3 = b"\x03" * 32
+salt4 = b"\x5a" * 16
+salt5 = b"\x96" * 64
+
+
+@pytest.fixture(scope="module")
+def MCHmacSecret(resetDevice,):
+    req = FidoRequest(extensions={"hmac-secret": True}, options={"rk": True})
+    res = resetDevice.sendMC(*req.toMC())
+    setattr(res, "request", req)
+    return res
+
+
+@pytest.fixture(scope="class")
+def sharedSecret(device, MCHmacSecret):
+    return device.client.pin_protocol.get_shared_secret()
+
+
+@pytest.fixture(scope="class")
+def cipher(device, sharedSecret):
+    key_agreement, shared_secret = sharedSecret
+    return Cipher(
+        algorithms.AES(shared_secret), modes.CBC(b"\x00" * 16), default_backend()
+    )
+
+
+class TestHmacSecret(object):
+    def test_hmac_secret_make_credential(self, MCHmacSecret):
+        assert MCHmacSecret.auth_data.extensions
+        assert "hmac-secret" in MCHmacSecret.auth_data.extensions
+        assert MCHmacSecret.auth_data.extensions["hmac-secret"] == True
+
+    def test_hmac_secret_info(self, info):
+        assert "hmac-secret" in info.extensions
+
+    def test_fake_extension(self, device):
+        req = FidoRequest(extensions={"tetris": True})
+        res = device.sendMC(*req.toMC())
+
+    def test_get_shared_secret(self, sharedSecret):
+        pass
+
+    @pytest.mark.parametrize("salts", [(salt1,), (salt1, salt2)])
+    def test_hmac_secret(self, device, MCHmacSecret, cipher, sharedSecret, salts):
+        print("salts:", salts)
+        key_agreement, shared_secret = sharedSecret
+        salt_enc, salt_auth = get_salt_params(cipher, shared_secret, salts)
+        req = FidoRequest(
+            extensions={"hmac-secret": {1: key_agreement, 2: salt_enc, 3: salt_auth}}
+        )
+        auth = device.sendGA(*req.toGA())
+
+        ext = auth.auth_data.extensions
+        assert ext
+        assert "hmac-secret" in ext
+        assert isinstance(ext["hmac-secret"], bytes)
+        assert len(ext["hmac-secret"]) == len(salts) * 32
+
+        verify(MCHmacSecret, auth, req.cdh)
+
+        dec = cipher.decryptor()
+        key = dec.update(ext["hmac-secret"]) + dec.finalize()
+
+        print(shannon_entropy(ext["hmac-secret"]))
+        if len(salts) == 1:
+            assert shannon_entropy(ext["hmac-secret"]) > 4.6
+            assert shannon_entropy(key) > 4.6
+        if len(salts) == 2:
+            assert shannon_entropy(ext["hmac-secret"]) > 5.4
+            assert shannon_entropy(key) > 5.4
+
+    def test_missing_keyAgreement(self, device, cipher, sharedSecret):
+        key_agreement, shared_secret = sharedSecret
+
+        salt_enc, salt_auth = get_salt_params(cipher, shared_secret, (salt3,))
+
+        req = FidoRequest(extensions={"hmac-secret": {2: salt_enc, 3: salt_auth}})
+
+        with pytest.raises(CtapError):
+            device.sendGA(*req.toGA())
+
+    def test_missing_saltAuth(self, device, cipher, sharedSecret):
+        key_agreement, shared_secret = sharedSecret
+
+        salt_enc, salt_auth = get_salt_params(cipher, shared_secret, (salt3,))
+
+        req = FidoRequest(extensions={"hmac-secret": {1: key_agreement, 2: salt_enc}})
+
+        with pytest.raises(CtapError) as e:
+            device.sendGA(*req.toGA())
+        assert e.value.code == CtapError.ERR.MISSING_PARAMETER
+
+    def test_missing_saltEnc(self, device, cipher, sharedSecret):
+        key_agreement, shared_secret = sharedSecret
+
+        salt_enc, salt_auth = get_salt_params(cipher, shared_secret, (salt3,))
+
+        req = FidoRequest(extensions={"hmac-secret": {1: key_agreement, 3: salt_auth}})
+
+        with pytest.raises(CtapError) as e:
+            device.sendGA(*req.toGA())
+        assert e.value.code == CtapError.ERR.MISSING_PARAMETER
+
+    def test_bad_auth(self, device, cipher, sharedSecret):
+
+        key_agreement, shared_secret = sharedSecret
+
+        salt_enc, salt_auth = get_salt_params(cipher, shared_secret, (salt3,))
+
+        bad_auth = list(salt_auth[:])
+        bad_auth[len(bad_auth) // 2] = bad_auth[len(bad_auth) // 2] ^ 1
+        bad_auth = bytes(bad_auth)
+
+        req = FidoRequest(
+            extensions={"hmac-secret": {1: key_agreement, 2: salt_enc, 3: bad_auth}}
+        )
+
+        with pytest.raises(CtapError) as e:
+            device.sendGA(*req.toGA())
+        assert e.value.code == CtapError.ERR.EXTENSION_FIRST
+
+    @pytest.mark.parametrize("salts", [(salt4,), (salt4, salt5)])
+    def test_invalid_salt_length(self, device, cipher, sharedSecret, salts):
+        key_agreement, shared_secret = sharedSecret
+        salt_enc, salt_auth = get_salt_params(cipher, shared_secret, salts)
+
+        req = FidoRequest(
+            extensions={"hmac-secret": {1: key_agreement, 2: salt_enc, 3: salt_auth}}
+        )
+
+        with pytest.raises(CtapError) as e:
+            device.sendGA(*req.toGA())
+        assert e.value.code == CtapError.ERR.INVALID_LENGTH
+        # auth = self.testGA(
+        # "Send GA request with incorrect salt length %d, expect INVALID_LENGTH"
+        #% len(salt_enc),
+        # rp["id"],
+        # cdh,
+        # other={
+        # "extensions": {
+        # "hmac-secret": {1: key_agreement, 2: salt_enc, 3: salt_auth}
+        # }
+        # },
+        # expectedError=CtapError.ERR.INVALID_LENGTH,
+        # )