To set up an HTTPS server using a self-signed certificate, you need: 1) A server certificate containing a public key 2) A private key 3) OpenSSL to generate these keys and a self-signed certificate 4) Python code to create an HTTPS server that uses the certificate and key to encrypt communication However, browsers will display certificate errors because self-signed certificates are not trusted; to resolve this, certificates must be obtained from a trusted certificate authority.

1. How to set https server
(using self-signed certificate)
Yoshinobu Tanno

2. Contents
1. Data flow between client and server
2. What do you need to implement an https server?
3. Making important data using OpenSSL
4. Making https server
5. Result

3. Data flow between client and server
Client Server
1. I want to see your site on https !
3. Thank you. I check you server certificate.
4. You are not a liar server!
I send session key which is encrypted by your public key.
5. OK. I decrypted session key using private key
6. Let’s start https using session key !
2. OK. I send you server certificate which includes public key.

4. What do you need to implement an https server?
Server
1. I want to see your site on https !
2. OK. I send you server certificate which includes public key.
3. Thank you. I check you server certificate.
4. You are not a liar server!
I send session key which is encrypted by your public key.
5. OK. I decrypted session key using private key
6. Let’s start https using session key !
Server certificate which includes public key
Private key

5. Making important data using OpenSSL
Command
openssl req -x509 -newkey rsa:4096 -sha256 -nodes -keyout
server.key -out server.crt -subj "/CN=example.com" -days 3650
Reference (Japanese)
https://qiita.com/masakielastic/items/05cd6a36bb6fb10fccf6

6. Making Https server
Python code
Reference (Japanese)
https://qiita.com/masakielastic/items/05cd6a36bb6fb10fccf6

7. Result
https communication is OK

8. Why browser outputs error (not secure) ?
Client Server
1. I want to see your site on https !
3. Thank you. I check you server certificate.
4. You are a liar server !?
I send session key which is encrypted by your public key.
5. OK. I decrypted session key using private key
6. Let’s start https using session key !
2. OK. I send you server certificate which includes public key.
Server certificate is not trust because server makes it.

9. How to make trusted server certificate
• Server need to apply server certificate to external agency
(Let's Encrypt etc…)
Server
1. I am not liar server. I want server certificate.
External agency
…
…
…
…
2. OK. Please prove that your domain is correct.
Reference
https://github.com/dwyl/learn-heroku/blob/master/SSL-certificate-step-by-step-setup-instructions.md