Is it typo?

[EunKyung-Kim]

This is the step in cluster3 of Setup.

According to your scenario, this should be about setup of istio-private-ingressgateway. Below sample describes istio-private-egressgateway.

cat > ./certificate3.conf <<EOF
[ req ]
encrypt_key = no
prompt = no
utf8 = yes
default_md = sha256
req_extensions = req_ext
x509_extensions = req_ext
distinguished_name = req_dn
[ req_ext ]
subjectKeyIdentifier = hash
basicConstraints = critical, CA:false
keyUsage = critical, digitalSignature, nonRepudiation
extendedKeyUsage = serverAuth
subjectAltName = critical, @san
[req_dn]
O=example Inc., department 3
CN=c3.example.com
[ san ]
URI.1 = spiffe://c3.example.com/istio-private-egressgateway
EOF