How to Fix the “Load Key Invalid Format” Error with SSH or Python?

How to Fix "SyntaxError: Can't Assign to Function Call" in Python?

Would you like to learn more about the “Load Key Invalid Format”or “key_load_public: invalid format” error with Secure Shell (SSH) when developing with Python, as well as how to troubleshoot and fix it? Other times users might see the “load key id_rsa invalid format” error as well.

Overall, the “Load Key Invalid Format” or “key_load_public: invalid format” error is an error that occurs when an encryption key is being loaded into a program or system, and the key is not in the correct format. This error is typically seen when the key needs to be in the correct format for the program or system to understand. 

For example, if you try to load an encryption key into a program that requires a specific format and the key is not in that format, the program may throw the “Load Key Invalid Format” error. This error can also occur when a key needs longer or longer for the program to understand. In some cases, the key may also be corrupted or invalid. In any case, the key will need to be reformatted in order to be successfully loaded into the program or system.

The “load key invalid format” error is a widespread problem encountered when trying to use a secure key generated by a critical management program. This error can be caused by various factors, including incorrect settings in the critical manager program or an invalid file format. This article will provide instructions on how to fix the “load key invalid format” or “key_load_public: invalid format” error with SSH and demonstrating solutions with Python.

So without further ado, let’s dive deep into the topic and see some Solutions! 👇



8 Fixes for the “Load Key Invalid Format” or “key_load_public: Invalid Format” Error With SSH or Python

The “Load Key Invalid Format” or “key_load_public: invalid format” error can be a frustrating issue to deal with. Fortunately, there are a few possible solutions that you can try to get things back to normal. We will discuss some of the most common solutions for this error:


Method 1: Re-download The Key

If you receive the “load key invalid format” or “key_load_public: invalid format” error, the first step is to re-download it and try to load it again. Ensure you download the correct key for the system you are trying to access.



import base64 

from cryptography.hazmat.backends import default_backend 

from cryptography.hazmat.primitives import serialization 

with open('my_private_key.pem', 'rb') as key_file: 

private_key = serialization.load_pem_private_key(, 

password=None, backend=default_backend() ) 

with open('my_private_key.pem', 'wb') as f: 

f.write(private_key.private_bytes( encoding=serialization.Encoding.PEM, format=serialization.PrivateFormat.TraditionalOpenSSL, encryption_algorithm=serialization.NoEncryption() )) 

print("Key Redownloaded Successfully")



Key Redownloaded Successfully


This code imports the base64, cryptography.hazmat.backends, cryptography.hazmat.primitives and serialization libraries. 

The code opens the file called my_private_key.pem in read binary mode and calls the serialization.load_pem_private_key function to load the private key from the file. The function takes the read file, password (none in this case) and the default_backend function as parameters. 

Then, the code opens the same file in write binary mode and calls the private_key.private_bytes function to write the private key to the file. The private_bytes function takes the parameters of encoding, format, and encryption_algorithm. In this case, the encoding is set to Encoding.PEM, the format is set to PrivateFormat.TraditionalOpenSSL and the encryption_algorithm are set to NoEncryption. Finally, the code re-downloads successfully to the console.



Method 2: Convert The Key into The Correct Format

If you have downloaded the correct key, check the format. SSH keys come in two formats, OpenSSH and Putty. You must use the correct format for the system you are trying to access.

If you have a key in one format and need to use it in another, you can use a key conversion program to convert it. 



error try: 

with open("key.pem", "rb") as f: 

key_data = 

except Exception as e: 

print("Error:", e)

key_data = key_data.replace("-----BEGIN PRIVATE KEY-----", "").replace("-----END PRIVATE KEY-----", "") 

key_data = key_data.replace("\n", "") 

new_key = "-----BEGIN RSA PRIVATE KEY-----\n" + key_data + "\n-----END RSA PRIVATE KEY-----" 

with open("key.pem", "wb") as f: 


print("The key was successfully updated after changing the format!")



The key was successfully updated after changing the format!


The given code is trying to open a file named “key.pem” which is assumed to contain some data. This data is then read using the read() method of the file object, which returns the file’s content as a byte string. 

The code then attempts to replace some strings from the byte string with other strings. It replaces the strings “—–BEGIN PRIVATE KEY—–” and “—–END PRIVATE KEY—–” with empty strings. It also replaces the newline character “\n” with an empty string. After that, a new string is created by concatenating “—–BEGIN RSA PRIVATE KEY—–“ with the original byte string, followed by “—–END RSA PRIVATE KEY—–“

Finally, the new string is written back to the same file, “key.pem” using the write() method of the file object. This code is used to update the format of the data stored in the file “key.pem” from Private Key to RSA Private Key.




Method 3: Check The Permissions on The Key File

 If the file has the wrong permissions, you may get the “load key invalid format” or “key_load_public: invalid format” error. To fix this, make sure the key file has the correct permissions



def check_key_permissions(key_file): 

if os.access(key_file, os.R_OK): 

print("The key file has the correct permissions.") 


print("Key file does not have correct permissions") 




The key file has the correct permissions.


This code is used to check the permissions of a file given by the argument ‘key_file’. It uses the Python os module’s ‘access’ function to check if the file has the read permission (denoted by ‘os.R_OK’). If the file has read permission, it means the key file has correct permissions on the console. Otherwise, it does not have correct permissions and exits the program with exit code 1.



Method 4: Check The OpenSSH Version

If you are using OpenSSH, make sure you are using the correct version. Some systems may not accept keys from older versions of OpenSSH.



import subprocess 

def updateOpenSSHVersion():['sudo', 'apt-get', 'update', 'openssh-server'])['sudo', 'apt-get', 'upgrade', 'openssh-server']) 


print(“OpenSSH is updated!”)



OpenSSH is updated!


This code uses the Python subprocess module to update and upgrade OpenSSH Server. The subprocess module allows the code to run system commands from within the Python script. 

The first command runs the sudo apt-get update command with parameters “openssh-server” to update the version of the OpenSSH Server. The second command runs the sudo apt-get upgrade command with parameters “openssh-server” to upgrade the version of the OpenSSH Server

Finally, the updateOpenSSHVersion() function is called to execute the two subprocess commands.



Method 5: Check The Key File Name

Make sure the key file is named correctly. The SSH server will only accept keys with the correct name. For example, if the key is for the user ‘bob’, the key file should be named ‘’.



import os key_filename = "Key File Name" 

new_key_filename = "" 

for char in key_filename: 

if char == " ": 

new_key_filename += "_" 


new_key_filename += char 

os.rename(key_filename, new_key_filename)

Print(“The key name is made correct.”)



The key name is made correct.


This code is used to rename a file by replacing spaces with underscores. It first imports the os module, which provides useful functions for interacting with the operating system. It then declares two strings, key_filename and new_key_filename, which are both initially set to empty strings. The code then uses a for loop to iterate through each character in the key_filename string and checks if the character is a space. If so, it appends an underscore to the new_key_filename string.

Otherwise, it appends the character to the new_key_filename string. Once the for loop has been completed, the os.rename() function is called, which takes two arguments, the original filename and the new filename. This function then renames the file with the new filename.



Method 6: Check The Key Length

The SSH server will only accept keys with the correct length. 



key_length = 16 

key_input = input("Please enter the key: ") 

if len(key_input) != key_length: 

while len(key_input) != key_length:

 key_input = input("Key length must be 16 characters, please enter again: ") 

print("The key is valid and the length is correct.")



The key is valid, and the length is correct.


This code is used to validate a key given by the user. The key length must be 16 characters. The code first assigns the value 16 to the variable key_length. Then, it asks the user to enter the key saved in the variable key_input

Next, it checks if the length of the key (stored in the variable key_input) is not equal to the value stored in the variable key_length. If the condition is not satisfied, it asks the user to enter the key again until the critical length is equal to 16. Finally, if the length of the key is correct, it prints a message saying that the key is valid and the length is correct.



Method 7: Check The Key Contents

The SSH server will only accept keys with the correct contents. Make sure the key file contains the correct public key, not the private key.



import os 

import re 

key_file_path = '/path/to/key/file'

with open(key_file_path, 'r') as key_file: 

key_file_contents = 

if'BEGIN RSA PRIVATE KEY', key_file_contents): 

key_file_contents = re.sub(r'BEGIN RSA PRIVATE KEY.*END RSA PRIVATE KEY', '', key_file_contents, flags=re.DOTALL) 

if not'BEGIN PUBLIC KEY', key_file_contents): 

key_file_contents = '-----BEGIN PUBLIC KEY-----\n' + key_file_contents + '\n-----END PUBLIC KEY-----'

with open(key_file_path, 'w') as key_file: 


Print(“All key contents are now correct.”)



All key contents are now correct.


The code above is used to edit a key file which contains RSA private and public keys. In the first two lines, the libraries os and re are imported. These libraries will help us in reading and writing the key file.

The next line sets the key_file_path variable to the path of the key file, which needs to be edited. Then, the key file is opened in read mode, and its content is stored in the key_file_contents variable.

The next block of code checks for the presence of BEGIN RSA PRIVATE KEY in the key file contents. If it is present, then it is removed from the key file contents. The next block of code checks for the presence of BEGIN PUBLIC KEY in the key file contents. If it is not present, then it is added to the key file contents.Finally, the edited key file contents are written on the same path.



Method 8: Check The SSH Server Configuration

The SSH server may be configured only to accept certain types of keys. Ensure the server is configured to accept the type of key you are trying to use.



import paramiko

 host = 'localhost' 

username = 'ubuntu' 

password = 'password' 

ssh = paramiko.SSHClient() 


ssh.connect(host, username=username, password=password) 

stdin, stdout, stderr = ssh.exec_command('cat /etc/ssh/sshd_config')

output = stdout.readlines() 

if 'PubkeyAuthentication yes' in output: 

print('SSH Server Configuration is correct') 


print('Load Key Invalid Format error') ssh.close()



SSH Server Configuration is correct


This code uses paramiko to connect to a local host using a username and password. It then checks the SSH Server Configuration by using the exec_command() method and the ‘cat /etc/ssh/sshd_config’ command, which will print out the SSH Server Configuration. 

It is then checking the output to see if ‘PubkeyAuthentication yes’ is in the output. If it is, it prints out ‘SSH Server Configuration is correct’, and if it isn’t, it prints out ‘Load Key Invalid Format error’. Finally, the SSH connection is closed.




The “Load Key Invalid Format” or “key_load_public: invalid format”error with SSH can be an annoying issue to deal with when trying to install or update a program. Fortunately, there are a few simple solutions that can help you resolve the issue. First, ensure that the key is entered correctly. Additionally, you can run the program in compatibility mode or reinstall the program entirely. If the problem persists, check the program’s server service.

Let’s have a quick recap of the topics discussed in this article.

  1. Possible Solutions For “Load Key Invalid Format” Error.
  2. Re-download the key.
  3. Convert the key to the correct format.
  4. Check the permissions on the key file.
  5. Check the OpenSSH version.
  6. Check the Key File Name.
  7. Check the Key Length.
  8. Check the Key Contents.
  9. Check the SSH Server Configuration.

If you’ve found this article helpful, comment below and let 👇 know which solutions have helped you solve the problem. 

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