Salt and hash a password in Python

Question

This code is supposed to hash a password with a salt   The salt and hashed password are being saved in the database   The password itself is not   Given the sensitive nature of the operation  I wanted to make sure everything was kosher     import hashlib import base64 import uuid  password    test password  salt       base64 urlsafe b64encode uuid uuid4   bytes    t sha   hashlib sha512   t sha update password salt  hashed password    base64 urlsafe b64encode t sha digest

User · Answer

The smart thing is not to write the crypto yourself but to use something like passlib: https://bitbucket.org/ecollins/passlib/wiki/Home

It is easy to mess up writing your crypto code in a secure way. The nasty thing is that with non crypto code you often immediately notice it when it is not working since your program crashes. While with crypto code you often only find out after it is to late and your data has been compromised. Therefor I think it is better to use a package written by someone else who is knowledgable about the subject and which is based on battle tested protocols.

Also passlib has some nice features which make it easy to use and also easy to upgrade to a newer password hashing protocol if an old protocol turns out to be broken.

Also just a single round of sha512 is more vulnerable to dictionary attacks. sha512 is designed to be fast and this is actually a bad thing when trying to store passwords securely. Other people have thought long and hard about all this sort issues so you better take advantage of this.

User · Answer

As of Python 3 4  the hashlib module in the standard library contains key derivation functions which are  designed for secure password hashing    So use one of those  like hashlib pbkdf2 hmac  with a salt generated using os urandom   from typing import Tuple import os import hashlib import hmac  def hash new password password  str  - gt  Tuple bytes  bytes               Hash the provided password with a randomly-generated salt and return the     salt and hash to store in the database              salt   os urandom 16      pw hash   hashlib pbkdf2 hmac  sha256   password encode    salt  100000      return salt  pw hash  def is correct password salt  bytes  pw hash  bytes  password  str  - gt  bool              Given a previously-stored salt and hash  and a password provided by a user     trying to log in  check whether the password is correct              return hmac compare digest          pw hash          hashlib pbkdf2 hmac  sha256   password encode    salt  100000           Example usage  salt  pw hash   hash new password  correct horse battery staple   assert is correct password salt  pw hash   correct horse battery staple   assert not is correct password salt  pw hash   Tr0ub4dor amp 3   assert not is correct password salt  pw hash   rosebud     Note that    The use of a 16-byte salt and 100000 iterations of PBKDF2 match the minimum numbers recommended in the Python docs  Further increasing the number of iterations will make your hashes slower to compute  and therefore more secure  os urandom always uses a cryptographically secure source of randomness hmac compare digest  used in is correct password  is basically just the    operator for strings but without the ability to short-circuit  which makes it immune to timing attacks  That probably doesn t really provide any extra security value  but it doesn t hurt  either  so I ve gone ahead and used it    For theory on what makes a good password hash and a list of other functions appropriate for hashing passwords with  see https   security stackexchange com q 211 29805

User · Answer

Here s my proposition  for i in range len rserver keys          salt   uuid uuid4   hex     print salt      mdp hash   rserver get rserver keys   i       rserver set rserver keys   i   hashlib sha256 salt encode     mdp hash encode    hexdigest     salt      rsalt set rserver keys   i   salt

User · Answer

passlib seems to be useful if you need to use hashes stored by an existing system  If you have control of the format  use a modern hash like bcrypt or scrypt   At this time  bcrypt seems to be much easier to use from python   passlib supports bcrypt  and it recommends installing py-bcrypt as a backend  http   pythonhosted org passlib lib passlib hash bcrypt html    You could also use py-bcrypt directly if you don t want to install passlib  The readme has examples of basic use   see also  How to use scrypt to generate hash for password and salt in Python

User · Answer

Firstly import -  import hashlib  uuid   Then change your code according to this in your method   uname   request form  uname   pwd request form  pwd   salt   hashlib md5 pwd encode      Then pass this salt and uname in your database sql query  below login is a table name   sql    insert into login values     uname       email       salt hexdigest

User · Answer

For this to work in Python 3 you ll need to UTF-8 encode for example   hashed password   hashlib sha512 password encode  utf-8     salt encode  utf-8    hexdigest     Otherwise you ll get       Traceback  most recent call last       File     line 1  in        hashed password   hashlib sha512 password   salt  hexdigest     TypeError  Unicode-objects must be encoded before hashing

User · Answer

Based on the other answers to this question  I ve implemented a new approach using bcrypt   Why use bcrypt  If I understand correctly  the argument to use bcrypt over SHA512 is that bcrypt is designed to be slow  bcrypt also has an option to adjust how slow you want it to be when generating the hashed password for the first time     The  12  is the number that dictates the  slowness  bcrypt hashpw password  bcrypt gensalt  12      Slow is desirable because if a malicious party gets their hands on the table containing hashed passwords  then it is much more difficult to brute force them    Implementation  def get hashed password plain text password         Hash a password for the first time          Using bcrypt  the salt is saved into the hash itself      return bcrypt hashpw plain text password  bcrypt gensalt     def check password plain text password  hashed password         Check hashed password  Using bcrypt  the salt is saved into the hash itself     return bcrypt checkpw plain text password  hashed password    Notes  I was able to install the library pretty easily in a linux system using   pip install py-bcrypt   However  I had more trouble installing it on my windows systems  It appears to need a patch  See this Stack Overflow question  py-bcrypt installing on win 7 64bit python

User · Answer

EDIT  This answer is wrong  A single iteration of SHA512 is fast  which makes it inappropriate for use as a password hashing function  Use one of the other answers here instead     Looks fine by me  However  I m pretty sure you don t actually need base64  You could just do this   import hashlib  uuid salt   uuid uuid4   hex hashed password   hashlib sha512 password   salt  hexdigest     If it doesn t create difficulties  you can get slightly more efficient storage in your database by storing the salt and hashed password as raw bytes rather than hex strings  To do so  replace hex with bytes and hexdigest with digest

User · Answer

I don  want to resurrect an old thread  but    anyone who wants to use a modern up to date secure solution  use argon2   https   pypi python org pypi argon2 cffi  It won the the password hashing competition    https   password-hashing net    It is easier to use than bcrypt  and it is more secure than bcrypt

[python] Salt and hash a password in Python

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