AES CBC 解密中的错误 65537

Question

I am currently doing a course on Coursera - Cryptography - I. There is an optional assignment, I am facing a syntactical issue with the library mentioned in it.

from Crypto.Cipher import AES

key = b'140b41b22a29beb4061bda66b6747e14'
iv = b'4ca00ff4c898d61e1edbf1800618fb28'
cipher = b'28a226d160dad07883d04e008a7897ee2e4b7465d5290d0c0e6c6822236e1daafb94ffe0c5da05d9476be028ad7c1d81'

obj = AES.new(key, AES.MODE_CBC, iv)

answer = obj.decrypt(cipher)
print(answer)

In the statement obj = AES.new(key, AES.MODE_CBC, iv) it throws an error ValueError: Error 65537 while instatiating the CBC mode Any fixes?

Answer 1

The values are encoded as hex strings. You need to use the decoded arrays of bytes.

Transform them with these lines, ahead of constructing your AES :

key = bytes.fromhex(key.decode('us-ascii'))
iv = iv.fromhex(iv.decode('us-ascii'))
cipher = cipher.fromhex(cipher.decode('us-ascii'))

(Or, simpler, define them as regular strings to avoid the need to .decode('us-ascii') .)

And you'll get:

b'Basic CBC mode encryption needs padding.\x08\x08\x08\x08\x08\x08\x08\x08'