Python - hashing binary value

Question

I wanted to use sha1 alghoritm to calculate the checksum of some data, the thing is that in python hashlib input is given as string.

Is it possible to calculate sha1 in python, but somehow give raw bytes as input?

I am asking because if I would want to calculate hash of an file, in C I would use openssl library and just pass normal bytes, but in Python I need to pass string, so if I would calculate hash of some specific file I would get different results in both languages.

Well, you could convert the text in the file to ascii and fire it through hashlib. I only think it makes difference for encodings other than single-byte. — Morten Jensen
– Morten Jensen, Commented Mar 10, 2013 at 16:11
I done some more reading and after viewing this question:stackoverflow.com/questions/2672326/… i think I can use struct module to build this byte-string representation of anything and pass it to hashlib. Correct me if I am wrong — Andna
– Andna, Commented Mar 10, 2013 at 16:14
Unless you know for certain that you are using a multi-byte charset in the file you want to hash, you can just pass it to the hashing function like you'd do in C. — Morten Jensen
– Morten Jensen, Commented Mar 10, 2013 at 16:16

tom · Accepted Answer · 2013-03-10 16:16:08Z

5

In Python 2.x, str objects can be arbitrary byte streams. So yes, you can just pass the data into the hashlib functions as strs.

>>> import hashlib
>>> "this is binary \0\1\2"
'this is binary \x00\x01\x02'
>>> hashlib.sha1("this is binary \0\1\2").hexdigest()
'17c27af39d476f662be60be7f25c8d3873041bb3'

answered Mar 10, 2013 at 16:16

tom

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6 Comments

Andna Over a year ago

Thanks, knowing this I can also use struct module to compute hash of for example for 4 byte integer.

Morten Jensen Over a year ago

@Andna you could do that with your old C hashing library too. I'm not sure why you'd involve the struct module for any of this. Can you elaborate?

Andna Over a year ago

Are you asking what I want to do this in Python?

Sassa NF Over a year ago

No you cannot. Try hashlib.sha1(u'\xcc\x88u') and see.

tom Over a year ago

@SassaNF that's because the u'...' causes the string to be a unicode object instead of a str object. To turn a unicode object into a str, you'll need to encode it. e.g. hashlib.sha1(u'\xcc\x88u'.encode("utf-8"))

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