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What are SSH Keys? - GeeksforGeeks

Last Updated : 02 Aug, 2025

The SSH (Secure Shell) is an access credential that is used in the SSH Protocol. In other words, it is a cryptographic network protocol that is used for transferring encrypted data over the network. The port number of SSH is 22. It allow users to connect with server, without having to remember or enter password for each system. It always comes in key pairs:

• Public key - Everyone can see it, no need to protect it. (for encryption function).
• Private key - Stays in computer, must be protected. (for decryption function).

Key pairs can be of the following types:

• User Key - If the public key and private key remain with the user.
• Host Key - If public key and private key are on a remote system.
• Session key - Used when a large amount of data is to be transmitted.

Secure Shell or SSH, is a protocol that allows you to connect securely to another computer over an unsecured network. It developed in 1995. SSH was designed to replace older methods like Telnet, which transmitted data in plain text.

Imagine a system administrator working from home who needs to manage a remote server at a company data center. Without SSH, they would have to worry about their login credentials being intercepted, leaving the server vulnerable to hackers. Instead of it after using SSH, the administrator establishes a secure connection that encrypts all data sent over the internet. They can now log in with their username and a private key, allowing them to safely execute commands on the server, transfer files, and make necessary updates, all of these without the risk of spying eyes watching their actions. This secure access is essential for maintaining the integrity of sensitive information of the company. ​SSH (Secure Shell) is an access credential that is used in the SSH Protocol. In other words, it is a cryptographic network protocol that is used for transferring encrypted data over the network.

• Encryption: Encrypted data is exchanged between the server and client, which ensures confidentiality and prevents unauthorized attacks on the system.
• Authentication: For authentication, SSH uses public and private key pairs which provide more security than traditional password authentication.
• Data Integrity: SSH provides Data Integrity of the message exchanged during the communication.
• Tunneling: Through SSH we can create secure tunnels for forwarding network connections over encrypted channels.

There are multiple functions performed by SSH Function, here below are some functions:

• SSH provides high security as it encrypts all messages of communication between client and server.
• SSH provides confidentiality.
• SSH allows remote login, hence is a better alternative to TELNET.
• SSH provides a secure File Transfer Protocol, which means we can transfer files over the Internet securely.
• SSH supports tunneling which provides more secure connection communication.

To provide security between a client and a server the SSH protocol uses encryption. All user authentication and file transfers are encrypted to protect the network against attacks.

There are majorly three major techniques used in SSH, which are

• Symmetric Cryptography: In Symmetric key cryptography the same key used for encrypting and decrypting the message, a unique single shared key is kept between the sender and reciever. For ex: DES (Data Encryption Standard) and AES (Advanced Encryption Standard).

• Asymmetric Cryptography: In Asymmetric key cryptography the key used for encrypting is different from the key used for decrypting the message. For ex: RSA (Rivest–Shamir–Adleman) and Digital Signature Algorithm.

• Hashing: Hashing is a procedure used in cryptography which convert variable length string to a fixed length string, this fixed length value is called hash value which is generated by hash function.

There are multiple commands supported by SSH protocol, you can tap on the link if you want to know commands in SSH.

How does generally WorkThe generalasymmetric?

For performing encryption and decryption it uses asymmetric cipher. There are many encryption methods:

rsa, dsa, ed25519 etc. 

The general procedure is:

• Public keys from the local computers (system) are passed to the server which is to be accessed.
• The server then identifies if the public key is registered.
• If so, the server then creates a new secret key and encrypts it with the public key which was sent to it via local computer.
• This encrypted code is sent to the local computer.
• This data is unlocked by the private key of the system and is sent to the server.
• The server after receiving this data verifies the local computer.
• SSH creates a route and all the encrypted data are transferred through it with no security issues.

SSH is key-based authentication that is not prone to brute-force attack. It is more convenient and secure than login IDs and passwords (which can be stolen in the middle). There is no exposure of valid credentials, if a server has been compromised.

Open your command prompt
type : ssh-keygen
Press enter
It will ask you for a location. Press Enter for default location.
If its already there, press 'y' to overwrite.
You may enter passphrase as you like, press enter. 

An example of generating an SSH Key pair in the latest version of Windows 10 is given below:

Generating SSH keys on Windows, Linux, generallywhich and Mac:

OMAC OsX and Linux : terminal (build in)
OWindows :- PuTTY 

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