SSH Key Fingerprint Generation and Extraction

SSH key pairs consist of a private key and a public key. The private key is kept securely on your local machine, while the public key is shared with remote servers or services you want to connect to securely. Generating a strong SSH key pair is crucial for ensuring the security of your remote connections. By generating an SSH key pair and extracting its fingerprint(s), you can securely authenticate and establish encrypted communication channels with remote systems. The fingerprint serves as a unique identifier for the public key, allowing you to verify its integrity and ensure that you are connecting to the intended server or service.

This method is particularly useful in scenarios where you need to securely connect to remote servers, transfer files, or manage remote systems over an insecure network. The SSH key pair and its fingerprint(s) provide a robust mechanism for authentication and encryption, ensuring that your connections are secure and protected against potential eavesdropping or man-in-the-middle attacks

Step 1 : Generate SSH key pair (RSA algorithm, 2048-bit key length)

ssh-keygen -t rsa -b 2048 -f ~/.ssh/id_rsa

Output:

The command-line tool for creating SSH keys is called ssh-keygen.

• ssh-keygen:To create SSH key pairs, use this command. A public key and a private key make up key pairs. For authentication purposes, the private key is stored locally on your system, and the public key is stored on distant computers.It facilitates the generation, conversion, and management of SSH key pairs, crucial for secure authentication and communication in SSH protocol-based systems.
• -t rsa: Indicates the kind of key to be generated; RSA is the example.
• -b 2048: Indicates how many bits are in the key. We are creating a 2048-bit key with this command, which is generally regarded as secure.
• -f ~/.ssh/id_rsa: Indicates the key pair’s filename. You can save the public key as ~/.ssh/id_rsa.pub and the private key as ~/.ssh/id_rsa.pub.

Step 2 : Extract fingerprint using MD5 hash algorithm

ssh-keygen -l -E md5 -f ~/.ssh/id_rsa.pub

Output:

A fingerprint is a distinct identity derived from a public key’s contents. It is employed to confirm the key’s integrity and authenticity

Message Digest Algorithm 5, or MD5, is a popular cryptographic hash algorithm. It generates a 32-character hexadecimal number that is a 128-bit hash value.

• -l : This command can be used to print the fingerprint of the specified public key file.
• -E md5 : Specifies the hash algorithm to use for fingerprint calculation, in this case it is MD5. MD5 is one of the available hash algorithms for SSH key fingerprints.
• -f ~/.ssh/id_rsa.pub : Specifies the filename of the public key file for which to generate the fingerprint.

Step 3 : Extract fingerprint using SHA-256 hash algorithm:

ssh-keygen -l -E sha256 -f ~/.ssh/id_rsa.pub

Output:

• -l: Ssh-keygen is instructed to display the fingerprint of the designated public key file when the -l option is used.By obtaining the fingerprint, we want to get a distinct identity generated from the public key’s contents, verifying its legitimacy and reliability.
• -E sha256: Specifies the hash algorithm to use for fingerprint calculation, in this case, SHA-256. SHA-256 is another available hash algorithm for SSH key fingerprints. The Secure Hash Algorithm 256-bit, or SHA-256, is a well-known cryptographic hash function that is resistant to attacks using cryptography. SHA-256 is a more safe and dependable fingerprint generator than less secure hash algorithms such as MD5.
• -f ~/.ssh/id_rsa.pub: We can specify the filename of the public key file for which the fingerprint will be computed by using the -f option.The file location of the public key file linked to the SSH key pair in this instance is ~/.ssh/id_rsa.pub.The public key produced by ssh-keygen is often stored in this filepath, where ~ stands for the user’s home directory.

A popular protocol for safe remote access to servers and other systems is called Secure Shell (SSH). The SSH key fingerprint is one of the essential elements of SSH authentication. We will discuss the definition of an SSH key fingerprint, its creation process, its significance for SSH authentication, and security and verification issues in this article.