Lesson 12

Date: 6/25/2017
Linux Password Security
Linux System Administration


MD5 and SHA512 Encryption algorithms

  • The crypt algorithms are the one way function. There is no reverse function to derive the original password from its hash.
  • md5-crypt can be divided into three phases. Initialization, loop, and finalization:
      1. Generate a simple md5 hash based on the salt and password
      2. Loop 1000 times, calculating a new md5 hash based on the previous hash concatenated with alternatingly the password and the salt.
      3. Use a special base64 encoding on the final hash to create the password hash string
  • sha512-crypt allows to specify a custom number of rounds, from 1000 to 999999999. the default is 5000.


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