CODEWITHSUNDEEP
pythonpython-2.7hashsha1
mawi
mawi

Reputation: 83

Making hash digest rounds

I'm trying to create a function that will take the sha1 hash and update it 500 times with itself, so for example:

>>> import hashlib
>>> d = hashlib.sha1()
>>> d.update("test")
>>> d.hexdigest()
'a94a8fe5ccb19ba61c4c0873d391e987982fbbd3'
>>> e = hashlib.sha1()
>>> e.update("a94a8fe5ccb19ba61c4c0873d391e987982fbbd3")
>>> e.hexdigest()
'c4033bff94b567a190e33faa551f411caef444f2'
>>>

What I want to do is take the hash of the original string test and rehash it into another hash, from the given hash.

I'm having some trouble doing this:

def sha1_rounds(string, salt=None, front=False, back=False, rounds=500, **placeholder):
    obj = hashlib.sha1()
    if salt is not None and front and not back:
        obj.update(salt + string)
    elif salt is not None and back and not front:
        obj.update(string + salt)
    else:
        obj.update(string)
    for _ in range(rounds):
        obj1 = obj.hexdigest()
        obj = obj.update(obj1)
    return obj.hexdigest()

When this code is run, it's giving me the following error:

Traceback (most recent call last):
  File "<pyshell#93>", line 1, in <module>
    sha1_rounds("test")
  File "<pyshell#92>", line 10, in sha1_rounds
    obj1 = obj.hexdigest()
AttributeError: 'NoneType' object has no attribute 'hexdigest'

If I'm understanding this correctly, what this error is telling me is that when I'm trying to re-update the hash object it's resulting in None. However, I've tried a few different things, and I'm not entirely sure how I can successfully do this. How can I create a new hash object inside of a for loop from a given hash?

Upvotes: 2

Views: 831

Answers (1)

mawi
mawi

Reputation: 83

I think I figured this out, by creating a new hash object and hexdigesting the string before the rounds, I might be able to speed up performance by moving the hash object creation outside of the for loop. If anyone has any other ideas, I would be excited to see them:

def sha1_rounds(string, salt=None, front=False, back=False, rounds=500, **placeholder):
    obj = hashlib.sha1()
    if salt is not None and front and not back:
        obj.update(salt + string)
    elif salt is not None and back and not front:
        obj.update(string + salt)
    else:
        obj.update(string)
        hashed = obj.hexdigest()
    for _ in range(rounds):
        obj1 = hashlib.sha1()
        obj1.update(hashed)
        hashed = obj1.hexdigest()
    return hashed

Upvotes: 1

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