using DES/3DES with python

Question

what is the best module /package in python to use des /3des for encryption /decryption. could someone provide example to encrypt data with des/3des on python.

Answer 1

pyDes can be used for both, DES and 3DES. Sample usage:

from pyDes import *

data = "Please encrypt my data"
k = des("DESCRYPT", CBC, "\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5)
d = k.encrypt(data)
print "Encrypted: %r" % d
print "Decrypted: %r" % k.decrypt(d)
assert k.decrypt(d, padmode=PAD_PKCS5) == data

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An alternative is the Chillkat Python Encryption Library which supports a lot of encryption algorithms (including DES & 3DES), but it is not free. Sample usage:

crypt.put_CryptAlgorithm("des")
crypt.put_CipherMode("cbc")
crypt.put_KeyLength(64)
crypt.put_PaddingScheme(0)
crypt.put_EncodingMode("hex")
ivHex = "0001020304050607"
crypt.SetEncodedIV(ivHex,"hex")
keyHex = "0001020304050607"
crypt.SetEncodedKey(keyHex,"hex")
encStr = crypt.encryptStringENC("The quick brown fox jumps over the lazy dog.")
print encStr
decStr = crypt.decryptStringENC(encStr)
print decStr

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Anyway, I hope that you are aware that neither DES nor 3DES are considered paritcularly safe nowadays, there are many better alternatives (AES in the first place if you want to stick to standards, or Twofish, Blowfish, etc...)

Answer 2

You can use the M2Crypto Python wrapper for OpenSSL. It has the advantage of being fast (as fast as OpenSSL), but the disadvantage of the documentation being limited.

Here is the example from my answer to "How to 3DES encrypt in Python using the M2Crypto wrapper?"

with open(keyfile, 'rb') as f:
    key = f.read()
encrypt = 1
cipher = Cipher(alg='des_ede3_ecb', key=key, op=encrypt, iv='\0'*16)
ciphertext = cipher.update(plaintext)
ciphertext += cipher.final()