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Salted hash implementation in Login, in nutshell



The best approach would be hashing the passwords, instead of encrypting them as key management becomes an issue.

Benefits of passwords in form of salted hash:
·         Real passwords are never stored/ displayed/ logged in the system
·         Salts makes dictionary attack very impractical as it’s very difficult to generate    re-computed hash table as salts are random
·         It’s easier to implement as no need of key management

A general approach would be like this (when storing):
·         Generate a long random salt using cryptographically strong functions such as SecureRandom in Java, when user is first time registering himself
·         Use the above salt and hash it with the user’s chosen password using standard and strong hashing algos like SHA 256
·         Now strore the Username, salted hash and respective salt in DB

When retrieving (authenticating user):
·         When the user submits his username-password, retrieve the user’s corresponding salt
·         Concatenate the salt with the user supplied password and apply the same hashing algo (SHA 256) and compute the salted hash
·         Now compare the newly computed salted hash with already stored salted hash against the username
·         If they match, let him in otherwise throw a generic login error, such as ‘Invalid Credentials’

Client side vs. Server side:
·         Always do hashing on server side, irrespective of client side hashing
·         The issue with client side hashing is , even it’s not in clear text, it is as good as a clear text password
·         If you do client side hashing, you need to depend on Javascript, which sometimes is disabled by user, or some browsers may not execute properly
·         Client side hashing is not replacement for TLS/ SSL. Protect all sensitive pages, such as login page over SSL

Constraint:
·         You may not be able to recover user’s original password, if user forgets it as the passwords are not in clear text. You can just users to update with a new password

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