hellman / libnum Goto Github PK

Will you be adding support for Python 3 in this?

This could be useful (I needed it just now)
I'm new to python so you may want to rewrite this.

def pkcs7(s, b):
    if len(s) % b == 0:
        return s
    need = len(s) / b + 1
    byte = need*b - len(s)
    return s + chr(byte)*byte

Function sqrtmod_prime_power appears to fail when the modular is a power of 2 instead of a power of an odd prime:

>>> list(libnum.sqrtmod_prime_power(3, 2, 3))
[7, 5, 1, 3]
>>> list(libnum.sqrtmod_prime_power(1, 2, 3))
[1, 3, 5, 7]

Here it erroneously found the same solutions for the equations x**2 == 3 (mod 8) and x**2 == 1 (mod 8).

The same wrong result is returned with sqrtmod as well:

>>> list(libnum.sqrtmod(3, {2: 3}))
[7, 5, 1, 3]

python libnum\setup.py install

Fails

running install
running build
running build_py
package init file 'libnum\__init__.py' not found (or not a regular file)
creating build
creating build\lib
creating build\lib\libnum
copying libnum\setup.py -> build\lib\libnum
error: package directory 'libnum\chains' does not exist

Going to the directory itself then running

python setup.py install

Succeeds

math.log(n, 2) doesn't produce exact results for large numbers, so numbers near a power of 2 can be returned incorrectly. The first example is:

In [43]: (140737488355328).bit_length()
Out[43]: 48

In [44]: len_in_bits(140737488355328)
Out[44]: 47

http://stackoverflow.com/q/9829578/125507
http://stackoverflow.com/q/2654149/125507

this is what I used in scipy to find the next hamming number:

        try:
            return n.bit_length()
        except AttributeError:
            # Fallback for Python <2.7
            return len(bin(n)) - 2

The fallback uses string processing, but this is fast because string operations are compiled C?

Python 2.7.12 (default, Nov 12 2018, 14:36:49)
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.

import libnum
libnum.s2n("abcd")
Traceback (most recent call last):
File "", line 1, in
File "/usr/local/lib/python2.7/dist-packages/libnum/strings.py", line 10, in s2n
return int(s.encode("utf-8").hex(), 16)
AttributeError: 'str' object has no attribute 'hex'

Polynomial in finite field might be important in number theory.