I've put in place the CBC and CTR modes of operation for block cipher encryption and decoding. I encrypted and decrypted every 16-byte block using AES. The ciphertext is prepended with the randomly selected 16-byte encryption IV. The PKCS#5/#7 padding method is employed for CBC. Take note that a distinct ciphertext is produced for each encryption of the same message using the same key. The same communication can be decrypted from several ciphertexts.
$ python script.py
-------------
BLOCK CIPHER MODE OF OPERATION
-------------
Enter preferred mode of operation [cbc/ctr]: ctr
Enter hex-encoded key: 36f18357be4dbd77f050515c73fcf9f2
Decrypt or encrypt?[d/e]: d
Enter hex-encoded cipher to decrypt: 69dda8455c7dd4254bf353b773304eec0ec7702330098ce7f7520d1cbbb20fc388d1b0adb5054dbd7370849dbf0b88d393f252e764f1f5f7ad97ef79d59ce29f5f51eeca32eabedd9afa9329
Decrypted message:
CTR mode lets you build a stream cipher from a block cipher.
Press any key to exit.
- AES (Advanced Encryption Standard)
- PKCS #5/#7 padding scheme as described in RFC 5652
01
02 02
03 03 03
04 04 04 04
05 05 05 05 05
06 06 06 06 06 06
etc.
Properties
Encryption parallelizable: No
Decryption parallelizable: Yes
Random read access: Yes
Properties
Encryption parallelizable: Yes
Decryption parallelizable: Yes
Random read access: Yes
- Key:
140b41b22a29beb4061bda66b6747e14
- The following cipher decrypts to
Basic CBC mode encryption needs padding.when the key above is used
4ca00ff4c898d61e1edbf1800618fb28
28a226d160dad07883d04e008a7897ee
2e4b7465d5290d0c0e6c6822236e1daa
fb94ffe0c5da05d9476be028ad7c1d81
- The following cipher decrypts to
Our implementation uses rand. IVwhen the key above is used.
5b68629feb8606f9a6667670b75b38a5
b4832d0f26e1ab7da33249de7d4afc48
e713ac646ace36e872ad5fb8a512428a
6e21364b0c374df45503473c5242a253
- Key:
36f18357be4dbd77f050515c73fcf9f2
- The following cipher decrypts to
CTR mode lets you build a stream cipher from a block cipher.when the key above is used.
69dda8455c7dd4254bf353b773304eec
0ec7702330098ce7f7520d1cbbb20fc3
88d1b0adb5054dbd7370849dbf0b88d3
93f252e764f1f5f7ad97ef79d59ce29f
5f51eeca32eabedd9afa9329
- The following cipher decrypts to
Always avoid the two time pad!when the key above is used.
770b80259ec33beb2561358a9f2dc617
e46218c0a53cbeca695ae45faa8952aa
0e311bde9d4e01726d3184c34451
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