modeOperation.py

from Crypto.Cipher import AES
from Crypto.Util import Counter


def cbcDecrypt(keyHexEncode, ctxtHexEncode):
    key = keyHexEncode.decode('hex')
    ctxt = ctxtHexEncode.decode('hex')
    blksz = len(key)
    # Extract the IV
    iv = ctxt[:blksz]
    aesObj = AES.new(key, AES.MODE_CBC, iv)

    # Decrypt chain for the rest of ciphertext
    ciphertext = ctxt[blksz:]
    ptxt = aesObj.decrypt(ciphertext)
    print(ptxt)
    return ptxt

"""
https://pycryptodome.readthedocs.io/en/latest/src/cipher/classic.html#ctr-mode
"""
def ctrDecrypt(keyHexEncode, ctxtHexEncode):
    key = keyHexEncode.decode('hex')
    ctxt = ctxtHexEncode.decode('hex')
    blksz = len(key)
    # Extract the IV
    iv = ctxt[:blksz]
    nonce = iv[:8]
    counter = int(iv[8:].encode('hex'), 16)
    aesObj = AES.new(key, AES.MODE_CTR, counter=Counter.new(64, prefix=nonce, initial_value=counter))
    #aesObj = AES.new(key, AES.MODE_CTR, nonce=nonce, initial_value=counter)

    # Decrypt chain for the rest of ciphertext
    ciphertext = ctxt[blksz:]
    ptxt = aesObj.decrypt(ciphertext)
    print(ptxt)
    return ptxt


if __name__ == '__main__':
    cbcDecrypt('140b41b22a29beb4061bda66b6747e14', '4ca00ff4c898d61e1edbf1800618fb2828a226d160dad07883d04e008a7897ee2e4b7465d5290d0c0e6c6822236e1daafb94ffe0c5da05d9476be028ad7c1d81')
    cbcDecrypt('140b41b22a29beb4061bda66b6747e14', '5b68629feb8606f9a6667670b75b38a5b4832d0f26e1ab7da33249de7d4afc48e713ac646ace36e872ad5fb8a512428a6e21364b0c374df45503473c5242a253')
    ctrDecrypt('36f18357be4dbd77f050515c73fcf9f2', '69dda8455c7dd4254bf353b773304eec0ec7702330098ce7f7520d1cbbb20fc388d1b0adb5054dbd7370849dbf0b88d393f252e764f1f5f7ad97ef79d59ce29f5f51eeca32eabedd9afa9329')
    ctrDecrypt('36f18357be4dbd77f050515c73fcf9f2', '770b80259ec33beb2561358a9f2dc617e46218c0a53cbeca695ae45faa8952aa0e311bde9d4e01726d3184c34451')