124 lines
5 KiB
Python
124 lines
5 KiB
Python
|
#
|
||
|
|
# KDF.py : a collection of Key Derivation Functions
|
||
|
|
#
|
||
|
|
# Part of the Python Cryptography Toolkit
|
||
|
|
#
|
||
|
|
# ===================================================================
|
||
|
|
# The contents of this file are dedicated to the public domain. To
|
||
|
|
# the extent that dedication to the public domain is not available,
|
||
|
|
# everyone is granted a worldwide, perpetual, royalty-free,
|
||
|
|
# non-exclusive license to exercise all rights associated with the
|
||
|
|
# contents of this file for any purpose whatsoever.
|
||
|
|
# No rights are reserved.
|
||
|
|
#
|
||
|
|
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
||
|
|
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
|
||
|
|
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
||
|
|
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
|
||
|
|
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
|
||
|
|
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
|
||
|
|
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
||
|
|
# SOFTWARE.
|
||
|
|
# ===================================================================
|
||
|
|
|
||
|
|
"""This file contains a collection of standard key derivation functions.
|
||
|
|
|
||
|
|
A key derivation function derives one or more secondary secret keys from
|
||
|
|
one primary secret (a master key or a pass phrase).
|
||
|
|
|
||
|
|
This is typically done to insulate the secondary keys from each other,
|
||
|
|
to avoid that leakage of a secondary key compromises the security of the
|
||
|
|
master key, or to thwart attacks on pass phrases (e.g. via rainbow tables).
|
||
|
|
|
||
|
|
:undocumented: __revision__
|
||
|
|
"""
|
||
|
|
|
||
|
|
__revision__ = "$Id$"
|
||
|
|
|
||
|
|
import math
|
||
|
|
import struct
|
||
|
|
|
||
|
|
from Crypto.Util.py3compat import *
|
||
|
|
from Crypto.Hash import SHA as SHA1, HMAC
|
||
|
|
from Crypto.Util.strxor import strxor
|
||
|
|
|
||
|
|
def PBKDF1(password, salt, dkLen, count=1000, hashAlgo=None):
|
||
|
|
"""Derive one key from a password (or passphrase).
|
||
|
|
|
||
|
|
This function performs key derivation according an old version of
|
||
|
|
the PKCS#5 standard (v1.5).
|
||
|
|
|
||
|
|
This algorithm is called ``PBKDF1``. Even though it is still described
|
||
|
|
in the latest version of the PKCS#5 standard (version 2, or RFC2898),
|
||
|
|
newer applications should use the more secure and versatile `PBKDF2` instead.
|
||
|
|
|
||
|
|
:Parameters:
|
||
|
|
password : string
|
||
|
|
The secret password or pass phrase to generate the key from.
|
||
|
|
salt : byte string
|
||
|
|
An 8 byte string to use for better protection from dictionary attacks.
|
||
|
|
This value does not need to be kept secret, but it should be randomly
|
||
|
|
chosen for each derivation.
|
||
|
|
dkLen : integer
|
||
|
|
The length of the desired key. Default is 16 bytes, suitable for instance for `Crypto.Cipher.AES`.
|
||
|
|
count : integer
|
||
|
|
The number of iterations to carry out. It's recommended to use at least 1000.
|
||
|
|
hashAlgo : module
|
||
|
|
The hash algorithm to use, as a module or an object from the `Crypto.Hash` package.
|
||
|
|
The digest length must be no shorter than ``dkLen``.
|
||
|
|
The default algorithm is `SHA1`.
|
||
|
|
|
||
|
|
:Return: A byte string of length `dkLen` that can be used as key.
|
||
|
|
"""
|
||
|
|
if not hashAlgo:
|
||
|
|
hashAlgo = SHA1
|
||
|
|
password = tobytes(password)
|
||
|
|
pHash = hashAlgo.new(password+salt)
|
||
|
|
digest = pHash.digest_size
|
||
|
|
if dkLen>digest:
|
||
|
|
raise ValueError("Selected hash algorithm has a too short digest (%d bytes)." % digest)
|
||
|
|
if len(salt)!=8:
|
||
|
|
raise ValueError("Salt is not 8 bytes long.")
|
||
|
|
for i in range(count-1):
|
||
|
|
pHash = pHash.new(pHash.digest())
|
||
|
|
return pHash.digest()[:dkLen]
|
||
|
|
|
||
|
|
def PBKDF2(password, salt, dkLen=16, count=1000, prf=None):
|
||
|
|
"""Derive one or more keys from a password (or passphrase).
|
||
|
|
|
||
|
|
This performs key derivation according to the PKCS#5 standard (v2.0),
|
||
|
|
by means of the ``PBKDF2`` algorithm.
|
||
|
|
|
||
|
|
:Parameters:
|
||
|
|
password : string
|
||
|
|
The secret password or pass phrase to generate the key from.
|
||
|
|
salt : string
|
||
|
|
A string to use for better protection from dictionary attacks.
|
||
|
|
This value does not need to be kept secret, but it should be randomly
|
||
|
|
chosen for each derivation. It is recommended to be at least 8 bytes long.
|
||
|
|
dkLen : integer
|
||
|
|
The cumulative length of the desired keys. Default is 16 bytes, suitable for instance for `Crypto.Cipher.AES`.
|
||
|
|
count : integer
|
||
|
|
The number of iterations to carry out. It's recommended to use at least 1000.
|
||
|
|
prf : callable
|
||
|
|
A pseudorandom function. It must be a function that returns a pseudorandom string
|
||
|
|
from two parameters: a secret and a salt. If not specified, HMAC-SHA1 is used.
|
||
|
|
|
||
|
|
:Return: A byte string of length `dkLen` that can be used as key material.
|
||
|
|
If you wanted multiple keys, just break up this string into segments of the desired length.
|
||
|
|
"""
|
||
|
|
password = tobytes(password)
|
||
|
|
if prf is None:
|
||
|
|
prf = lambda p,s: HMAC.new(p,s,SHA1).digest()
|
||
|
|
key = b('')
|
||
|
|
i = 1
|
||
|
|
while len(key)<dkLen:
|
||
|
|
U = previousU = prf(password,salt+struct.pack(">I", i))
|
||
|
|
for j in range(count-1):
|
||
|
|
previousU = t = prf(password,previousU)
|
||
|
|
U = strxor(U,t)
|
||
|
|
key += U
|
||
|
|
i = i + 1
|
||
|
|
return key[:dkLen]
|
||
|
|
|