Image encryption and decryption using Pycrypto

Question

How can I encrypt images using the Pycrypto python library? I found some text encrypting examples on internet, but I didn't find the same with images. Can anyone help me?

Solution

It is just the same as encrypting or decrypting text.

Example

First import some modules:

from Crypto.Cipher import AES
from Crypto import Random

After that, let us generate a key and an initialisation vector.

key = Random.new().read(AES.block_size)
iv = Random.new().read(AES.block_size)

Encryption

Now the code below loads an input file input.jpg and encrypts it, and afterwards it saves the encrypted data on a file encrypted.enc. In this example, the AES block cipher is used with the CFB mode of operation.

input_file = open("input.jpg")
input_data = input_file.read()
input_file.close()

cfb_cipher = AES.new(key, AES.MODE_CFB, iv)
enc_data = cfb_cipher.encrypt(input_data)

enc_file = open("encrypted.enc", "w")
enc_file.write(enc_data)
enc_file.close()

Decryption

Finally, the code below loads the encrypted file encrypted.enc and decrypts it, and afterwards it saves the decrypted data on a file output.jpg.

enc_file2 = open("encrypted.enc")
enc_data2 = enc_file2.read()
enc_file2.close()

cfb_decipher = AES.new(key, AES.MODE_CFB, iv)
plain_data = cfb_decipher.decrypt(enc_data2)

output_file = open("output.jpg", "w")
output_file.write(plain_data)
output_file.close()

Note

For simplicity, the encryption and the decryption have been done in the same Python session, so the variables key and iv have been reused immediately, and to test this solution you have to do encryption and decryption in the same Python session. Of course, if you want to decrypt later in a separate session you will need to save key and iv and to reload them when you need to decrypt.

Testing the solution

Now you can open the output.jpg file and you should see an image which is identical to the one in input.jpg.

Comments

[Siddharth Choudhary]

Well I am trying to do something similar but am not able to convert the image to byte data and not being able to even read it through your code because it gets error of 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte. Can you give a glimpse on that

[Kubuntuer82]

Is the image stored in a file?

[Siddharth Choudhary]

Nope, it's just an image. I actually had a look and have figured out a way to do it and it is totally different from the way you are doing it. I will soon post the answer here.

[Kubuntuer82]

Perfect @SiddharthChoudhary, well done! I look forward to seeing it :)

[Siddharth Choudhary]

I can't answer this question anymore because people have closed it.

[user311790]

The input of the image in your code is giving an error

[Kubuntuer82]

@user311790 what kind of error? It works perfectly on my machine and with my interpreter. Is your image named input.jpg ? What Python version are you using (2 or 3)? Is PyCrypto installed in your machine?

[user311790]

Python 2.7.15, with pycryptodome installed, the code is working but the output image is not opening.

[Kubuntuer82]

Remember that in the answer, by output file I mean output.jpg and not encrypted.enc... file output.jpg is unencrypted and it is just generated to test the correctness of the encryption, it should open and should be identical to input.jpg (I also tested them using the diff tool). File encrypted.enc cannot be opened because it is encrypted, so if you consider that as the output file, then it's expected that it cannot be opened.