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2017-11-28 Security

Encryption Vs Cryptographic Hash

Encryption vs Cryptographic Hash#

What is the difference between encryption and a cryptographic hash

Encryption#

Create a secret message to send to someone and they do the opposite to decrypt it. Encryption can always be reversed if you know the process or have the correct key.

Hashing#

Hashing is a process that cannot be undone. It always changes the same input into the same output. It is one way and usually creates output of a specific size. eg. 256 bits.

Cryptographic hashing adds random data, a salt, that makes the input data more different and unique.

Example Using Bcrypt#

Install bcrypt

pip install flask-bcrypt

Import

from flask_bcrypt import generate_password_hash

Generate the hash

>>> generate_password_hash('secret')

Output

b'$2b$12$w/x0Q9FnFydn/vZX26iz7eSNhJUavlm93SI.Kuv4uMATe031dKcpG'
  • bmeans byte-string
  • $2b tells you it is bcrypt
  • $12 is the number of rounds
  • rest is the hash

If you set the rounds really high, it takes longer:

>>> generate_password_hash('secret', 15)

When a password attempt fails, it is good practise to increase the rounds so it takeslonger to check the hash.Slowing down crackers.

Checking password#

How do you heck it though…

>>> hashed_pw = generate_password_hash('secret', 12)
>>> hashed_pw
b'$2b$12$tE/SrlIDeO3Efs5lI77ZxeY3hzoAd1on2Lbx0SZnxBEARuSwBvEri'
>>> hashed_pw == generate_password_hash('secret', 12)
False

The above does not work. Youhave to check it with check_password_hash

from flask_bcrypt import check_password_hash

then test it:

>>> check_password_hash(hashed_pw, 'secret')