Networking Secure Protocols

TLS

• Secure Socket Layer (SSL) was developed by Netscape Communications and released SSL 2.0 in 1995.
• Transport Layer Security (TLS) was developed by Internet Engineering Task Force (IETF) as an upgrade to SSL 3.0 in 1999.
• In 2018, TLS 1.3 was released as a major overhaul for its previous version after two decades.
• Nowadays, many protocols received an upgrade to secure protocols with the simple addition of TLS.
• Examples: HTTPS, SMTPS, POP3S, IMAPS, DoT(DNS over TLS), etc.
• The first step for every server (or client) that needs to identify itself is to get a signed TLS certificate.
• Generally, it is a paid process but https://letsencrypt.org/ lets you get a certificate for free.
• A self-signed certificate cannot prove the server’s authenticity as no third party has confirmed it.

HTTPS

• HTTPS stands for Hypertext Transfer Protocol Secure.
• It's basically HTTP over TLS.
• By default, HTTPS communicates over the port 443.
• The communication in HTTPS happens in the following order.
  • 3 packets for three-ways TCP handshake.
  • Several packets to negotiate TLS protocol.
  • Encrypted packets of application data.
• The encrypted data can be decrypted only if the key is available.

SMTPS, POP3S, and IMAPS

Protocol	Transport Protocol	Default Port Number
SSH	TCP	22
HTTPS	TCP	443
FTPS	TCP	990
SMTPS	TCP	465 and 587
POP3S	TCP	995
IMAPS	TCP	993

SSH

• Although, telnet is convenient to login to remote systems it is less secure.
• Telnet sends data in cleartext, which anyone can intercept and read.
• Secure Shell (SSH) protocol was developed by Tatu Ylönen and released SSH-1 in 1995.
• A more secure version, SSH-2, was defined in 1996.
• OpenSSH, an opensource implementation of SSH was released by OpenBSD developers in 1999.
• Nowadays, most ssh clients use OpenSSH libraries and source code.
• OpenSSH offers the following benefits.
  • Secure authentication
  • Confidentiality
  • Integrity
  • Tunneling
  • X11 Forwarding - SSH allows you to use the graphical application over the network.
• TELNET server listens on port 23, the SSH server listens on port 22.

SFTP and FTPS

• SFTP stands for SSH File Transfer Protocol.
• It is part of the SSH protocol suite and shares the same port number, 22.
• FTPS stands for File Transfer Protocol Secure.
• FTPS uses TLS to securely transfer files.
• SFTP and FTPS are different.

VPN

• VPN stands for Virtual Private Network.
• VPN connect all its offices and sites to the main branch so that any device can access the shared resources.

Closing notes

• Executing chromium --ssl-key-log-file=~/ssl-key.log dumps the TLS keys to the ssl-key.log file.
• Use this key file to decrypt the packets in wireshark.