Friday, October 9, 2015

Storing passwords in a secure way in a SQL Server database

"Everybody would agree that passwords should be secure, so users should consider these points when they choose passwords. Such as using a mix of characters and special symbols, not using simple words, using a combination of special symbols, letters and numbers, etc. But all these considerations are not enough if passwords are stored in an unsecure way.
In database applications passwords are usually stored in the database, so storing passwords in the database should be implemented very carefully. It is obvious that storing passwords in the table with plain text is very vulnerable, because if an attacker accesses the database he/she can steal users' passwords. It is indisputable that passwords in a database should be encrypted and made undecipherable as much as possible."
"Let's see how to encrypt and store passwords in a SQL Server database. For encrypting passwords we'll use one-way hashing algorithms. These algorithms map the input value to encrypted output and for the same input it generates the same output text. Also there is no decryption algorithm. It means that it's impossible to revert to the original value using encrypted output. 
The HASHBYTES function in SQL Server returns a hash for the input value generated with a given algorithm. Possible algorithms for this function are MD2, MD4, MD5, SHA, SHA1 and starting with SQL Server 2012 also include SHA2_256 and SHA2_512. We will choose the strongest - SHA2_512 - for our example (it generates a 130 symbol hash and uses 64 bytes). We should also consider the fact that the stronger algorithm, the more time that is needed for hashing than for weaker algorithms...."

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