diff --git a/tests/common.py b/tests/common.py
index fb37e69732..4379aad560 100644
--- a/tests/common.py
+++ b/tests/common.py
@@ -263,3 +263,14 @@ def get_test_address(client: "Client") -> str:
     """Fetch a testnet address on a fixed path. Useful to make a pin/passphrase
     protected call, or to identify the root secret (seed+passphrase)"""
     return btc.get_address(client, "Testnet", TEST_ADDRESS_N)
+
+
+def compact_size(n) -> bytes:
+    if n < 253:
+        return n.to_bytes(1, "little")
+    elif n < 0x1_0000:
+        return bytes([253]) + n.to_bytes(2, "little")
+    elif n < 0x1_0000_0000:
+        return bytes([254]) + n.to_bytes(4, "little")
+    else:
+        return bytes([255]) + n.to_bytes(8, "little")
diff --git a/tests/device_tests/bitcoin/payment_req.py b/tests/device_tests/bitcoin/payment_req.py
index 9ab2d4dad8..5d987706df 100644
--- a/tests/device_tests/bitcoin/payment_req.py
+++ b/tests/device_tests/bitcoin/payment_req.py
@@ -5,6 +5,8 @@ from ecdsa import ECDH, SECP256k1, SigningKey
 
 from trezorlib import btc, messages
 
+from ...common import compact_size
+
 SLIP44 = 1  # Testnet
 
 TextMemo = namedtuple("TextMemo", "text")
@@ -20,13 +22,7 @@ payment_req_signer = SigningKey.from_string(
 
 
 def hash_bytes_prefixed(hasher, data):
-    n = len(data)
-    if n < 253:
-        hasher.update(n.to_bytes(1, "little"))
-    elif n < 0x1_0000:
-        hasher.update(bytes([253]))
-        hasher.update(n.to_bytes(2, "little"))
-
+    hasher.update(compact_size(len(data)))
     hasher.update(data)
 
 
diff --git a/tests/device_tests/test_authenticate_device.py b/tests/device_tests/test_authenticate_device.py
new file mode 100644
index 0000000000..f197b13f4e
--- /dev/null
+++ b/tests/device_tests/test_authenticate_device.py
@@ -0,0 +1,77 @@
+import pytest
+from cryptography import x509
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.asymmetric import ec
+from cryptography.x509 import extensions as ext
+
+from trezorlib import device
+from trezorlib.debuglink import TrezorClientDebugLink as Client
+
+from ..common import compact_size
+
+pytestmark = [pytest.mark.skip_t1, pytest.mark.skip_t2]
+
+ROOT_PUBLIC_KEY = bytes.fromhex(
+    "04626d58aca84f0fcb52ea63f0eb08de1067b8d406574a715d5e7928f4b67f113a00fb5c5918e74d2327311946c446b242c20fe7347482999bdc1e229b94e27d96"
+)
+
+
+@pytest.mark.parametrize(
+    "challenge",
+    (
+        b"",
+        b"hello world",
+        b"\x00" * 1024,
+        bytes.fromhex(
+            "21f3d40e63c304d0312f62eb824113efd72ba1ee02bef6777e7f8a7b6f67ba16"
+        ),
+    ),
+)
+def test_authenticate_device(client: Client, challenge: bytes) -> None:
+    # NOTE Applications must generate a random challenge for each request.
+
+    # Issue an AuthenticateDevice challenge to Trezor.
+    proof = device.authenticate(client, challenge)
+    certs = [x509.load_der_x509_certificate(cert) for cert in proof.certificates]
+
+    # Verify the last certificate in the certificate chain against trust anchor.
+    root_public_key = ec.EllipticCurvePublicKey.from_encoded_point(
+        ec.SECP256R1(), ROOT_PUBLIC_KEY
+    )
+    root_public_key.verify(
+        certs[-1].signature,
+        certs[-1].tbs_certificate_bytes,
+        certs[-1].signature_algorithm_parameters,
+    )
+
+    # Verify the certificate chain.
+    for cert, ca_cert in zip(certs, certs[1:]):
+        assert cert.issuer == ca_cert.subject
+
+        ca_basic_constraints = ca_cert.extensions.get_extension_for_class(
+            ext.BasicConstraints
+        ).value
+        assert ca_basic_constraints.ca is True
+
+        try:
+            basic_constraints = cert.extensions.get_extension_for_class(
+                ext.BasicConstraints
+            ).value
+            if basic_constraints.ca:
+                assert basic_constraints.path_length < ca_basic_constraints.path_length
+        except ext.ExtensionNotFound:
+            pass
+
+        ca_cert.public_key().verify(
+            cert.signature,
+            cert.tbs_certificate_bytes,
+            cert.signature_algorithm_parameters,
+        )
+
+    # Verify that the common name matches the Trezor model.
+    common_name = cert.subject.get_attributes_for_oid(x509.oid.NameOID.COMMON_NAME)[0]
+    assert common_name.value.startswith(client.features.internal_model)
+
+    # Verify the signature of the challenge.
+    data = b"\x13AuthenticateDevice:" + compact_size(len(challenge)) + challenge
+    certs[0].public_key().verify(proof.signature, data, ec.ECDSA(hashes.SHA256()))
diff --git a/tests/ui_tests/fixtures.json b/tests/ui_tests/fixtures.json
index 3b4c1708e6..fd000334da 100644
--- a/tests/ui_tests/fixtures.json
+++ b/tests/ui_tests/fixtures.json
@@ -1760,6 +1760,10 @@
 "TR_stellar-test_stellar.py::test_sign_tx[timebounds-0-1575234180]": "9e1f884816d80415ef9b925309d5502852d8bade9c632f2d715d0a2cdecb1204",
 "TR_stellar-test_stellar.py::test_sign_tx[timebounds-461535181-0]": "afc84260d5f7991a516ead25a0f77c34ec14ef2b3de3595adc1c50624657ac0a",
 "TR_stellar-test_stellar.py::test_sign_tx[timebounds-461535181-1575234180]": "8fcc98ebb2f76f36f85c313131478d29b3b2ba79e2ef5993afa3cb7a663ed63a",
+"TR_test_authenticate_device.py::test_authenticate_device[!\\xf3\\xd4\\x0ec\\xc3\\x04\\xd01-b\\xeb\\x82-e4b4eb3a": "5bbde07a26ce37bd72d0c792c4dc9807c169c9fc731d1bcf30a72a5f2da7f602",
+"TR_test_authenticate_device.py::test_authenticate_device[\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\-d824e03c": "5bbde07a26ce37bd72d0c792c4dc9807c169c9fc731d1bcf30a72a5f2da7f602",
+"TR_test_authenticate_device.py::test_authenticate_device[]": "5bbde07a26ce37bd72d0c792c4dc9807c169c9fc731d1bcf30a72a5f2da7f602",
+"TR_test_authenticate_device.py::test_authenticate_device[hello world]": "5bbde07a26ce37bd72d0c792c4dc9807c169c9fc731d1bcf30a72a5f2da7f602",
 "TR_test_autolock.py::test_apply_auto_lock_delay": "cf93576944395035a45cf62f4b4b22387c595af7646e1863b07bdcc38ccfbb20",
 "TR_test_autolock.py::test_apply_auto_lock_delay_out_of_range[0]": "674ca13c50b342d80ca47ed49bcfaa846bb07db2ba30d6e1414c96db8375457b",
 "TR_test_autolock.py::test_apply_auto_lock_delay_out_of_range[1]": "674ca13c50b342d80ca47ed49bcfaa846bb07db2ba30d6e1414c96db8375457b",