What does the b in front of the decrypted plaintext mean in pycrypto?

Question

I'm trying to encrypt a plain text using DES algorithm implemented in PyCrypto. However, when I print the encrypted text and then decrypt it using the generated encrypted text an additional b seems to get added every time. Is this an error or just something else that I'm being ignorant about?

Here's the code sample:

des = DES.new('01234567', DES.MODE_ECB)
text = input('Enter plain text: ')
cipher_text = des.encrypt(text)
print('Cipher Text:' + str(cipher_text))
decipher_text = des.decrypt(ciphertext=cipher_text)
print('Deciphered text is: ' + str(decipher_text))

And the resultant output:

Enter plain text: abcdefgh
Cipher Text:b'\xec\xc2\x9e\xd9] a\xd0'
Deciphered text is: b'abcdefgh'

DES should not be used for new work, it is not secure and has been superseded by AES. Do not use ECB mode, it is insecure, see [ECB mode](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_Codebook_.28ECB.29), scroll down to the Penguin. Instead use CBC mode with a random IV, just prefix the encrypted data with the IV for use in decryption, it does not need to be secret. — zaph, Apr 15 '17 at 12:01
Why not "just mess around" with a current secure encryption algorithm, it is no harder. Since you are just messing around it is a good time to learn about CBC mode and padding. — zaph, Apr 15 '17 at 12:05
Thanks. Definitely, could you direct me to some resources that I could refer? — Vivek Giri, Apr 15 '17 at 12:11
[Package Crypto :: Package Cipher :: Module AES](https://www.dlitz.net/software/pycrypto/api/current/) — zaph, Apr 15 '17 at 12:21
**Never use [ECB mode](http://crypto.stackexchange.com/q/14487/13022)**. It's deterministic and therefore not semantically secure. You should at the very least use a randomized mode like [CBC](http://crypto.stackexchange.com/q/22260/13022) or [CTR](http://crypto.stackexchange.com/a/2378/13022). It is better to authenticate your ciphertexts so that attacks like a [padding oracle attack](http://crypto.stackexchange.com/q/18185/13022) are not possible. This can be done with authenticated modes like GCM or EAX, or with an [encrypt-then-MAC](http://crypto.stackexchange.com/q/202/13022) scheme. — Artjom B., Apr 15 '17 at 16:09

score 4 · Accepted Answer · answered Apr 15 '17 at 11:35

4

The b indictes this is a binary string.

answered Apr 15 '17 at 11:35

CodeCupboard

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Do i need to convert the string or is it okay if I keep it that way? – Vivek Giri Apr 15 '17 at 11:37
It's up to you. If you want to change it to a normal string use b"string".decode("ascii") – CodeCupboard Apr 15 '17 at 11:38
It throws this error `UnicodeDecodeError: 'ascii' codec can't decode byte 0xec in position 0: invalid continuation byte` – Vivek Giri Apr 15 '17 at 11:44
If that doesn't work you could try decipher_text.decode("utf-8") – CodeCupboard Apr 15 '17 at 11:45
1

http://stackoverflow.com/questions/17615414/how-to-convert-binary-string-to-normal-string-in-python3 this contains some of the information I have suggested. – CodeCupboard Apr 15 '17 at 11:47
1

The b indicates it is a bytes object. And no, you can't convert every bytes object to a string. – President James K. Polk Apr 15 '17 at 14:22
2

@JamesKPolk: ^ It depends. If it's a binary encoding of some text format (UTF-8, Latin-1, Shift-JIS, you name it), you can `.decode()` it accordingly. But _in general case,_ an arbitrary sequence of bytes cannot be decoded as a text ("Unicode") string. – 9000 Apr 15 '17 at 17:12
Correct, and the output of an encryption operation is an arbitrary sequence of bytes. – President James K. Polk Apr 15 '17 at 18:43
@JamesKPolk Is that why I'm getting the error while converting? – Vivek Giri Apr 16 '17 at 04:12

What does the b in front of the decrypted plaintext mean in pycrypto?

1 Answers1