cd /usr/src/linux-headers-$(uname -r)/certs

# Create a config file for the certificate
cat <<EOF > x509.genkey
[ req ]
default_bits = 4096
distinguished_name = req_distinguished_name
prompt = no
x509_extensions = myexts

[ req_distinguished_name ]
CN = Modules

[ myexts ]
basicConstraints=critical,CA:FALSE
keyUsage=digitalSignature
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid
EOF

# Generate the key and certificate
openssl req -new -nodes -utf8 -sha512 -days 36500 -batch \
  -x509 -config x509.genkey -outform DER \
  -out signing_key.x509 -keyout signing_key.pem