diff --git a/.gitignore b/.gitignore
index 83a2569ddf0..795e2605e00 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,8 @@ htmlcov/
 .coverage.*
 .cache/
 .mypy_cache/
+/tests/keys/localhost.crt
+/tests/keys/localhost.key
 
 # Windows
 Thumbs.db
diff --git a/conftest.py b/conftest.py
index b39d644a511..95d4eaef632 100644
--- a/conftest.py
+++ b/conftest.py
@@ -2,6 +2,8 @@
 
 import pytest
 
+from tests.keys import generate_keys
+
 
 def _py_files(folder):
     return (str(p) for p in Path(folder).rglob('*.py'))
@@ -53,3 +55,7 @@ def reactor_pytest(request):
 def only_asyncio(request, reactor_pytest):
     if request.node.get_closest_marker('only_asyncio') and reactor_pytest != 'asyncio':
         pytest.skip('This test is only run with --reactor=asyncio')
+
+
+# Generate localhost certificate files, needed by some tests
+generate_keys()
diff --git a/tests/keys/__init__.py b/tests/keys/__init__.py
new file mode 100644
index 00000000000..da202be4da9
--- /dev/null
+++ b/tests/keys/__init__.py
@@ -0,0 +1,63 @@
+import os
+from datetime import datetime, timedelta
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography.hazmat.primitives.hashes import SHA256
+from cryptography.hazmat.primitives.serialization import (
+    Encoding,
+    NoEncryption,
+    PrivateFormat,
+)
+from cryptography.x509 import (
+    CertificateBuilder,
+    DNSName,
+    Name,
+    NameAttribute,
+    random_serial_number,
+    SubjectAlternativeName,
+)
+from cryptography.x509.oid import NameOID
+
+
+# https://cryptography.io/en/latest/x509/tutorial/#creating-a-self-signed-certificate
+def generate_keys():
+    folder = os.path.dirname(__file__)
+
+    key = rsa.generate_private_key(
+        public_exponent=65537,
+        key_size=2048,
+        backend=default_backend(),
+    )
+    with open(os.path.join(folder, 'localhost.key'), "wb") as f:
+        f.write(
+            key.private_bytes(
+                encoding=Encoding.PEM,
+                format=PrivateFormat.TraditionalOpenSSL,
+                encryption_algorithm=NoEncryption(),
+            )
+        )
+
+    subject = issuer = Name(
+        [
+            NameAttribute(NameOID.COUNTRY_NAME, u"IE"),
+            NameAttribute(NameOID.ORGANIZATION_NAME, u"Scrapy"),
+            NameAttribute(NameOID.COMMON_NAME, u"localhost"),
+        ]
+    )
+    cert = (
+        CertificateBuilder()
+        .subject_name(subject)
+        .issuer_name(issuer)
+        .public_key(key.public_key())
+        .serial_number(random_serial_number())
+        .not_valid_before(datetime.utcnow())
+        .not_valid_after(datetime.utcnow() + timedelta(days=10))
+        .add_extension(
+            SubjectAlternativeName([DNSName(u"localhost")]),
+            critical=False,
+        )
+        .sign(key, SHA256(), default_backend())
+    )
+    with open(os.path.join(folder, 'localhost.crt'), "wb") as f:
+        f.write(cert.public_bytes(Encoding.PEM))
diff --git a/tests/keys/localhost.crt b/tests/keys/localhost.crt
deleted file mode 100644
index 0cf5256d8da..00000000000
--- a/tests/keys/localhost.crt
+++ /dev/null
@@ -1,20 +0,0 @@
------BEGIN CERTIFICATE-----
-MIIDRTCCAi2gAwIBAgIUGoISfeW3LwSWHC52ORXdZY9pNLswDQYJKoZIhvcNAQEL
-BQAwMjELMAkGA1UEBhMCSUUxDzANBgNVBAoMBlNjcmFweTESMBAGA1UEAwwJbG9j
-YWxob3N0MB4XDTIwMDYyODEyNTQxNVoXDTIxMDYyODEyNTQxNVowMjELMAkGA1UE
-BhMCSUUxDzANBgNVBAoMBlNjcmFweTESMBAGA1UEAwwJbG9jYWxob3N0MIIBIjAN
-BgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvCLxfTEQuIdf8JhiHrbVkGHYrNSK
-2XD2TCPaSIpJ2KKlFUrIz3A9tWlOfLnWabS5od89yOebhYj4DN/Qm2TViGg1mtWe
-pD1K2YWd1Af+hhAw5D+TpW2RH9TVhX7Ey5osWcl+0uy+RlKZE8qum72xi1vxWOmH
-wYw06iN8klQ3JfP2/eLRXBQjsh7WW0dbJ7yLvG6UFz1RbhFTtlxeIMenzNsHaMg7
-56Ru57/MMbaBwdBttXVzJDQ7imo8njuxDMszliC/QgIdBUBFzA2LB5qpr+v+laDN
-cN9t9Q9stsu446dFnRoofxJjMFW7lLu6h/lwP5r0kfeUkMDhXJ4mb6KwfwIDAQAB
-o1MwUTAdBgNVHQ4EFgQUVEdXn8ha2FA73zcy1Ia0FQMzMEYwHwYDVR0jBBgwFoAU
-VEdXn8ha2FA73zcy1Ia0FQMzMEYwDwYDVR0TAQH/BAUwAwEB/zANBgkqhkiG9w0B
-AQsFAAOCAQEAZpGBPsexMD+IwcMNIgc7FiaJsb8E30C9vWxgdnkpapi9zLJ4yiHQ
-VxkV9RTezUEADkaDj+2qFveamWTzJLnphgaaUpVeMcYACPhRVOYXidNrZyTmHIsX
-FwaTzAggW6CP7JxAcpxH0f9+NWFCZI36FihRdwuWyvrUl7rsXaexu0SOI/Ck0oWf
-2IW+jo67TSmcbte+J8wq77DX32mVLb/2nqpItH4T2Di+XjVBARACVOSdgdlo7lZE
-W8mSEXqP2BVx8JGG8X1znNLHcmjVj4EtkpH0wkYzpC4cvGkTsUcU7CU7ZyVUp+Bb
-dPMVxyRKWfAjRJc8o5Ot1mgHrx5coOtzAA==
------END CERTIFICATE-----
diff --git a/tests/keys/localhost.key b/tests/keys/localhost.key
deleted file mode 100644
index 8fc373bddcb..00000000000
--- a/tests/keys/localhost.key
+++ /dev/null
@@ -1,28 +0,0 @@
------BEGIN PRIVATE KEY-----
-MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQC8IvF9MRC4h1/w
-mGIettWQYdis1IrZcPZMI9pIiknYoqUVSsjPcD21aU58udZptLmh3z3I55uFiPgM
-39CbZNWIaDWa1Z6kPUrZhZ3UB/6GEDDkP5OlbZEf1NWFfsTLmixZyX7S7L5GUpkT
-yq6bvbGLW/FY6YfBjDTqI3ySVDcl8/b94tFcFCOyHtZbR1snvIu8bpQXPVFuEVO2
-XF4gx6fM2wdoyDvnpG7nv8wxtoHB0G21dXMkNDuKajyeO7EMyzOWIL9CAh0FQEXM
-DYsHmqmv6/6VoM1w3231D2y2y7jjp0WdGih/EmMwVbuUu7qH+XA/mvSR95SQwOFc
-niZvorB/AgMBAAECggEAHVpSVRb/pdqxNEeCH4qlHWa2uJhcpXpDYzPAzcqNpPgT
-S5QkaoD3j8NDVKBl/I4O3FuJNzwzfo0VLmUJFgWQbzzbCDJGExfhArkfG8K3ilEi
-X6ovrgK/PrklKzPRHncKbmPKnrwDH9OpQHZB8diRx81rhVTCModehh1NRUNQa2I1
-QzFC7uyXx3duoIsI5QXVeEGuwHZfqIY/z+9SscdVFL6elXTPFUzBzcmAqQgdgWKN
-HXgX22LE0rAu8NnRvOZZWt4/nOjvlCFCPTB11NgthmKlVnsx4H7gpQ2OPh4bZ+0W
-birVEtZ3E1jxoGvw1FzxyqqpGkcanRMa8QWzK4JwuQKBgQDrgclpkqZrgHB/TC1p
-hLvsdflGI2SGs+c/mYR3GEjf0kJtI88WL5fj1QezdkDyOpwxFvnLslswfzdtzvis
-vksGysV35vhMPQUcmWhvzA7Pdxdv4BZr+ckER0SAYBBxg9KYZyxewGb5XzB8Cz2o
-8V+YpwrMAOYGuXHTfafv4CKlTQKBgQDMgetvV9/E3HNtKsATiPIwT3e1MzyPXigq
-12NkHSZa6s4yqm/h/fSUn54sJbhx+OtRRhktOo0aB34tcogtrJyClvCPdRAP/4Qi
-M43FjKo2cWiubWvtWlOZU04bpClG324q420rK7dCA2stID/Fa0sMQgAAyPH8TGMo
-gbvyrk4W+wKBgQDMIOnYZTF0epaH8BponJFaqwMOhTzr+OGW4dTMebMotZG4EdK8
-kzIfW5XaOsSecKjTb+vCYGzkA1CjEEPBTwuu7nDstblAM5/Lozi/tmqb7sjUwrIM
-kyxmVfONJjb6fV07lioCUtiui5B15DRkzBqlMRyNqLW43GJKA19d7rN4/QKBgCzy
-kRBTu/bEjQn9T2H7w18i2CiXLkREaYeg91NVpMxutwsjspt0+YCA5H7He5ZxIycl
-xPrP15tU8kKC3bNMMMny6sRc8j7R5fSuaAZ3OCHnIx7TJdlw9NbKHGyu0/Ojv87l
-VWUbopd7sN6mK930CvaSuvVxNN5C27hXazuXW8ppAoGBANcWsenNKpCJgF0cNPHX
-abPaWfcs5FKMNz8gEdGk3B1z/KBpYz59smPwurYVCXaWE6iv99sDOP7CVneF02sV
-SqyNzVhcVSG788uB3CwnpEvm7ydoH89L5dvYekAHP8RJulhWCK45lXkHLiYGKvhv
-PWuPk5VX+qF78JhUhPO3nfnu
------END PRIVATE KEY-----