# Example of block cipher usage with the pycrypto library. Ignore the warning about libgmp
from sage import *
from Crypto.Cipher import AES
from Crypto import Random
import binascii

def createKey(string):
    string = str(string)
    if len(string) > 16:
        return string[0:16]
    else:
        return string + '0'*(16 - len(string))
    

key = createKey("password")
IV = '0123456789abcdef'

AEScipher = AES.new(key, AES.MODE_CFB, IV)

#Credit for this universal truth goes to Neal Stephenson - Cryptonomicon
message = """This made him a grad student, and grad students existed not to learn things
but to relieve the tenured faculty members of tiresome burdens such as educating people and doing research."""

c = IV + AEScipher.encrypt(message)

print "Original message: ", message,"\n"
print "Original bytes:   ",binascii.hexlify(message),"\n"
print "Ciphertext bytes: ",binascii.hexlify(c[16:]),"\n"

decryptor = AES.new(key, AES.MODE_CFB, IV)
decryptedMessage = AEScipher.decrypt(c)

print "Original IV        : ", IV, "\n"
print "Extracted IV from c: ", c[0:16], "\n"



#Note the IV is prepended to encryptions, so we select from 16 bytes onwards.
print "Decrypted message: ",decryptedMessage[16:],"\n"

# Other options include md5
import hashlib
H = hashlib.sha256()

print H.hexdigest()
H.update("")
print H.hexdigest()
H.update("World-class cereal-eating is a dance of fine compromises.")
print H.hexdigest()
H.update("The giant heaping bowl of sodden cereal, awash in milk, is the mark of the novice.")
print H.hexdigest()

print "\n"
#May want to convert to an integer for use in algorithms. 
#usage : int(NumberInBase,base)
intDigest = H.hexdigest()
intDigest = int(H.hexdigest(),16)
print H.hexdigest(), "in base 10: ", intDigest