Cryptography
1. Simple Hashing
Use the hashlib library for hashing functions like MD5 and SHA-1
1 import hashlib
2
3 text="Mary had a little lamb"
4
5 md5 = hashlib.md5()
6 md5.update(text)
7
8 sha1 = hashlib.sha1()
9 sha1.update(text)
10
11 print md5.digest()
12 # Prints the (binary) digest. Actually it is unsuitable for display
13
14 print md5.hexdigest()
15 # 'e946adb45d4299def2071880d30136d4'
16
17 print sha1.hexdigest()
18 # 'bac9388d0498fb378e528d35abd05792291af182'
19
20 print "MD5 = %d bits, SHA-1 = %d bits" % (len(md5.hexdigest()) * 4, len(sha1.hexdigest()) * 4)
21 # 'MD5 = 128 bits, SHA-1 = 160 bits'
22 # ... always!
23
24 # One liners!
25 print hashlib.sha1(text).hexdigest()
26 # 'bac9388d0498fb378e528d35abd05792291af182'
27
28 # Use update() when you are processing multiple blocks of data
29
30 md5 = hashlib.md5()
31 for x in open('/home/sandipb/.bashrc'): md5.update(x)
32 print md5.hexdigest() # >>> '20ede33b79459b380c9c72a731f4cc04'
33 #
34 # Using the Linux tool
35 # $ md5sum ~/.bashrc
36 # 20ede33b79459b380c9c72a731f4cc04 /home/sandipb/.bashrc
37 #
38
hashlib supports md5(), sha1(), sha224(), sha256(), sha384(), and sha512()
2. Hashing with a symmetric key
Using a shared secret/salt, the hashlib methods can be made more difficult to crack.
Use the hmac module for this.
1 import hmac, hashlib
2
3 text="Mary had a little lamb"
4 secret="wolf"
5
6 hash = hmac.new( secret, digestmod=hashlib.sha1)
7 hash.update(text)
8 print hash.hexdigest()
9 # '01872dea0802454638b605093107b297c8f0e915'
10
11 # or
12
13 print hmac.new('wolf', text, hashlib.sha1).hexdigest()
14 # '01872dea0802454638b605093107b297c8f0e915'
15