Telnet vs SSH
Secure Shell, commonly known as SSH, and Telnet are two network protocols that have been used widely at one point in time or another. They are both used to connect to remote servers in order to facilitate some sort of communications. The primary difference, which also led to one superseding the other, is in security. SSH offers security mechanisms that protect the users against anyone with malicious intent while Telnet has no security measures whatsoever.
Telnet was designed to work within a private network and not across a public network where threats can appear. Because of this, all the data is transmitted in plain text, including passwords. This is a major security issue and the developers of SSH used encryptions to make it harder for other people to sniff the password and other relevant information. Telnet also omits another safety measure called authentication. This ensures that the source of the data is still the same device and not another computer. Without authentication, another person can intercept the communication and do what he wishes. This is also addressed in SSH as it uses a public key to authenticate the source of the data.
Due to the security measures that were necessary for SSH to be used in public networks, each packet contains less data to make room for the data of the security mechanisms. In order to transmit the same amount of data, you would need to take-up a lot more bandwidth. This is called overhead and was such a major issue back when internet speeds were very low because it translates to a performance hit.
The security issues of Telnet forced a lot of people to use SSH in order to protect themselves. It didn’t take a long time before SSH replaced Telnet in a great majority of its uses. Telnet did not fade away though as it is still used in some areas, mostly in testing and debugging. Telnet extensions were developed to provide security but they are not used in most Telnet implementations.
Summary:
1. SSH and Telnet commonly serves the same purpose
2. SSH is more secure compared to Telnet
3. SSH encrypts the data while Telnet sends data in plain text
4. SSH uses a public key for authentication while Telnet does not use any authentication
5. SSH adds a bit more overhead to the bandwidth compared to Telnet
6. Telnet has been all but replaced by SSH in almost all uses
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