Skip to content

Instantly share code, notes, and snippets.

@bonsaiviking
Created May 23, 2013 20:10
Show Gist options
  • Save bonsaiviking/5639034 to your computer and use it in GitHub Desktop.
Save bonsaiviking/5639034 to your computer and use it in GitHub Desktop.
SHA1 implementation in pure Python
#!/usr/bin/env python
import struct
def leftrotate(i, n):
return ((i << n) & 0xffffffff) | (i >> (32 - n))
class SHA1(object):
def __init__(self, data=""):
self.h = [
0x67452301,
0xEFCDAB89,
0x98BADCFE,
0x10325476,
0xC3D2E1F0
]
self.remainder = data
self.count = 0
def _add_chunk(self, chunk):
self.count += 1
w = list( struct.unpack(">16I", chunk) + (None,) * (80-16) )
for i in xrange(16, 80):
n = w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16]
w[i] = leftrotate(n, 1)
a,b,c,d,e = self.h
for i in xrange(80):
f = None
k = None
if i < 20:
f = (b & c) ^ (~b & d)
k = 0x5A827999
elif i < 40:
f = b ^ c ^ d
k = 0x6ED9EBA1
elif i < 60:
f = (b & c) ^ (b & d) ^ (c & d)
k = 0x8F1BBCDC
else:
f = b ^ c ^ d
k = 0xCA62C1D6
temp = (leftrotate(a,5) + f + e + k + w[i]) % 2**32
e = d
d = c
c = leftrotate(b, 30)
b = a
a = temp
self.h[0] = (self.h[0] + a) % 2**32
self.h[1] = (self.h[1] + b) % 2**32
self.h[2] = (self.h[2] + c) % 2**32
self.h[3] = (self.h[3] + d) % 2**32
self.h[4] = (self.h[4] + e) % 2**32
def add(self, data):
message = self.remainder + data
r = len(message) % 64
if r != 0:
self.remainder = message[-r:]
else:
self.remainder = ""
for chunk in xrange(0, len(message)-r, 64):
self._add_chunk( message[chunk:chunk+64] )
return self
def finish(self):
l = len(self.remainder) + 64 * self.count
self.add( "\x80" + "\x00" * ((55 - l) % 64) + struct.pack(">Q", l * 8) )
h = tuple(x for x in self.h)
self.__init__()
return struct.pack(">5I", *h)
@BenWiederhake
Copy link

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment