Software⏱️ 4 min read📅 2026-06-11

How to Fix: ssh: Error loading key "./id_rsa": invalid format

Invalid SSH key format error resolved by re-generating the private key.

Quick Answer: Try re-generating the private key using a tool like OpenSSL, and then add it to the SSH agent.

📋 Table of Contents

  1. 🛑 Root Causes of the Error
  2. 🚀 How to Resolve This Issue
  3. ✨ Wrapping Up

The error 'ssh: Error loading key "./id_rsa": invalid format' occurs when the ssh client is unable to load a private key file, in this case, './id_rsa'. This issue affects users who rely on SSH for secure remote access and is frustrating because it prevents them from connecting to their systems.

This problem can be particularly vexing when the same key works seamlessly in another environment, such as a clean virtual machine. The fact that GNOME successfully adds the key during login but fails with ssh-add -L suggests a configuration issue on the user's system.

🛑 Root Causes of the Error

  • The primary reason for this error is that the private key file contains an encrypted format, which is incompatible with some ssh versions or configurations. The 'Proc-Type: 4,ENCRYPTED' line in the key file indicates that it was generated using a tool like PuTTYgen or a similar encryption method.
  • An alternative cause could be a mismatch between the encryption algorithm used to generate the private key and the one expected by the ssh client. This might occur if the user has changed their system's OpenSSL settings or used an outdated version of OpenSSH.

🚀 How to Resolve This Issue

Fixing the Private Key Format

  1. Step 1: Step 1: Check the private key file format to ensure it matches the expected format. The 'Proc-Type' line should indicate that the key is encrypted, and the 'DEK-Info' field should specify the encryption algorithm used.
  2. Step 2: Step 2: If the key is indeed encrypted, use a tool like OpenSSL or PuTTYgen to decrypt it. You can do this by running the command `openssl rsa -in ./id_rsa -out decrypted_key.pem` (for RSA keys) or `puttygen ./id_rsa -Oq -Fp` (for PGP keys).
  3. Step 3: Step 3: Once you have decrypted the key, try adding it to your ssh agent using `ssh-add decrypted_key.pem`. If this fails, proceed with method 2.

Using a New Private Key

  1. Step 1: Step 1: Generate a new private key file using OpenSSL or PuTTYgen. The command to generate an RSA key is `openssl genrsa -out ./new_id_rsa 2048`, and for PGP keys, it's `puttygen -Oq -Fp`.
  2. Step 2: Step 2: Copy the contents of the new key file into your ssh agent using `ssh-add ./new_id_rsa`.

✨ Wrapping Up

To resolve the 'ssh: Error loading key "./id_rsa": invalid format' issue, first check if the private key file contains an encrypted format and decrypt it if necessary. If decryption fails or is not applicable, generate a new private key and add it to your ssh agent. By following these steps, you should be able to regain access to your system using SSH.

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