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EECS 354 Network Security. Passwords and Cryptography. Cracking a Hash. Modern hashing techniques are essentially uncrackable for unpatterned passwords of >7 characters But, lucky for hackers: Users choose bad passwords Administrators don’t use modern hashing methods. Some Examples.

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EECS 354Network Security

Passwords and Cryptography


Cracking a Hash

  • Modern hashing techniques are essentially uncrackable for unpatterned passwords of >7 characters

  • But, lucky for hackers:

    • Users choose bad passwords

    • Administrators don’t use modern hashing methods


Some Examples

  • 2013 Adobe breach: At least 28 million passwords in Triple DES

  • 2013 Cupid Media breach: 42 million passwords in plain text

  • 2011 Sony Playstation breach: 77 million passwords and credit card numbers in ?

  • 2010 Gawker breach: 1 million passwords in DES


Stolen Passwords

  • Eventually, someone usually notices their database has been hacked

  • Before:

    • Administrative access? Data tampering? Data collection?

  • After:

    • Users reuse passwords

      • Database associates password with identifying info

        • email, username, real name

        • grep for .gov, sensitive accounts

      • Leads to more sensitive data

        • Hacking email, social media


Dictionary Attacks

  • Effective against basic hash functions

    • MD5, SHA1, SHA2, etc

  • Dictionaries vary in size

  • Append, prepend, mutate dictionary entries

  • Password lists are also common for cracking (can be in the millions)

  • Password salting

    • Users with the same password won’t be cracked simultaneously


Dictionary Attacks

  • Here’s one word from your dictionary: password

  • With simple operations you can crack:

    • password123

    • p4ssw0rd

    • Password

    • Password2014


“Good” Hashing

  • People don’t notice if it takes one second to verify their password

    • Method: Use hashing. A lot. ~100,000 times, repeatedly. And a long salt.

    • Standard: PBKDF2

    • Alternatives: bcrypt, scrypt

      • Strength varies in password length, character diversity

  • brute force: useless (huge key space)dictionary: bad passwords are still bad


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