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Password (in)security

Password (in)security

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The 7th June 2012 Linkedin was hacked. More than 6 million LinkedIn passwords was compromised. The real shocking news was not the theft but the fact that the attackers were able to decrypt many of these passwords. Why it happened? The answer is simple: a bad design of the password security. In this talk I presented how to choose "secure" user's passwords and how to safely store it from a programmer's perspective.
This talk has been presented during the MOCA 2012, http://moca.olografix.org/moca2012

The 7th June 2012 Linkedin was hacked. More than 6 million LinkedIn passwords was compromised. The real shocking news was not the theft but the fact that the attackers were able to decrypt many of these passwords. Why it happened? The answer is simple: a bad design of the password security. In this talk I presented how to choose "secure" user's passwords and how to safely store it from a programmer's perspective.
This talk has been presented during the MOCA 2012, http://moca.olografix.org/moca2012

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Password (in)security

  1. 1. Password (in)security How to generate and store passwords in a secure way by Enrico “cerin0” Zimuel
  2. 2. About me 1998 Enrico “cerin0” Zimuel Developer since Texas Instruments TI99/4A Research programmer, Informatics institute of UvA (Amsterdam) Core team of the open source project Zend Framework Co-author of the books “Segreti, Spie Codici Cifrati”, “Come si fa a usare la firma digitale”, “PHP Best Practices” Founder of the PHP User Group Torino http://www.zimuel.it
  3. 3. Password A password is a secret word or string of characters that is used for authentication.
  4. 4. User perspective: How to choose a “secure” password? Developer perspective: How to store a password in a secure way?
  5. 5. Password security Basically every security system is based on password.
  6. 6. When security fails...
  7. 7. linkedin.com Hack: 6th June 2012 More than 6 million passwords was compromised SHA1 password
  8. 8. eharmony.com Hack: 6th June 2012 More than 1.5 million passwords was compromised SHA1 password
  9. 9. last.fm Hack: 7th June 2012 ? million passwords was compromised MD5 password
  10. 10. yahoo.com Hack: 12th June 2012 443K passwords was compromised SQL injection, password in plaintext!
  11. 11. How to choose a “robust” user's password
  12. 12. Some best practices: ● No personal information ● A long pass phrase is better than a shorter random jumble of characters ● At least 10 characters long ● Don't use the same password for everything ● Change your password from time to time
  13. 13. http://howsecureismypassword.net/
  14. 14. Developers Force the user to generate robust password
  15. 15. Developers How to store a password in a secure way?
  16. 16. Old school (deprecated) Use hash algorithms like MD5 or SHA1
  17. 17. New school (deprecated?) Use hash algorithm + salt (a random string).
  18. 18. Using hash + salt Prevent dictionary attacks? YES Prevent brute force attacks? NO
  19. 19. Brute forcing attacks CPU power is growing (multi-core) GPU are rendering password security useless Use a Cloud system (n-CPU)
  20. 20. Brute forcing with a GPU Source: www.nvidia.com
  21. 21. GPU and CUDA CUDA™ is a parallel computing platform and programming model invented by NVIDIA
  22. 22. Extreme GPU Bruteforcer using NVIDIA GTS250 ~ $100 Algorithm Speed 8 chars 9 chars 10 chars md5($pass) 426 million p/s 6 days 1 year 62 years md5($pass.$salt) 170 million p/s 14 days 2 ½ years 156 years sha1($pass) 85 million p/s 29 days 5 years 313 years sha1($pass.$salt) 80 million p/s 31 days 5 years 332 years Password of 62 characters (a-z, A-Z, 0-9) Source: http://www.insidepro.com/eng/egb.shtml
  23. 23. IGHASHGPU ATI HD 5970 ~ $700 Algorithm Speed 8 chars 9 chars 10 chars md5($pass) 5600 million p/s 10 hours 27 days 4 ½ years sha1($pass) 2300 million p/s 26 hours 68 days 11 ½ years Password of 62 characters (a-z, A-Z, 0-9) Source: http://www.golubev.com/hashgpu.htm
  24. 24. Whitepixel 4 Dual HD 5970 ~ $2800 Algorithm Speed 8 chars 9 chars 10 chars md5($pass) 33 billion p/s 1 ½ hour 4 ½ days 294 days Password of 62 characters (a-z, A-Z, 0-9) Source: http://blog.zorinaq.com/?e=42
  25. 25. Secure algorithms for password storing ●Hash + salt + stretching (i.e. PBKDF2) ● bcrypt ● scrypt
  26. 26. Hash + salt + stretching ● Stretching = iterate (hash + salt) n-times key = ““ for 1 to n­times do   key = hash(key + password + salt)
  27. 27. How to estimate the number of iterations? ●The number of iterations depends on the CPU speed, should take around 1 sec to be considered secure ● For instance, this PHP code: <?php $key=''; for ($i=0;$i<NUM_ITERATIONS;$i++) {     $key= hash('sha512',$key.$salt.$password); } runs in 900 ms with NUM_ITERATIONS= 40'000 using an Intel Core 2 at 2.1Ghz
  28. 28. PBKDF2 ● PBKDF2 (Password-Based Key Derivation Function 2) is a key derivation function that is part of RSA Laboratories' Public-Key Cryptography Standards (PKCS) series, specifically PKCS #5 v2.0 ● PBKDF2 applies a pseudorandom function, such as a cryptographic hash, cipher, or HMAC to the input password or passphrase along with a salt value and repeats the process many times to produce a derived key, which can then be used as a cryptographic key in subsequent operations
  29. 29. PBKDF2 in PHP PBKDF2 in PHP (Zend Framework 2.0) function calc($hash, $password, $salt, $iterations, $length) { $num = ceil($length / Hmac::getOutputSize($hash,  Hmac::OUTPUT_BINARY)); $result = ''; for ($block = 1; $block <= $num; $block++) { $hmac = Hmac::compute($password, $hash, $salt . pack('N',  $block), Hmac::OUTPUT_BINARY);     $mix = $hmac;     for ($i = 1; $i < $iterations; $i++) {     $hmac = Hmac::compute($password, $hash, $hmac,    Hmac::OUTPUT_BINARY);     $mix ^= $hmac;     }     $result .= $mix; } return substr($result, 0, $length); }
  30. 30. bcrypt ● http://bcrypt.sourceforge.net/ ● bcrypt uses Blowfish cipher + iterations to generate secure hash values ● bcrypt is secure against brute force or dictionary attacks because is slow, very slow (that means attacks need huge amount of time to be completed)
  31. 31. bcrypt parameters ●The algorithm needs a salt value and a work factor parameter (cost), which allows you to determine how expensive the bcrypt function will be ●The cost value depends on the CPU speed, check on your system! I suggest to set at least 1 second.
  32. 32. bcrypt in PHP ● bcrypt is implemented in PHP with the crypt() function: $salt = substr(str_replace('+', '.',                 base64_encode($salt)), 0, 22);  $hash = crypt($password,'$2a$'.$cost.'$'.$salt); ● For instance, $password= 'thisIsTheSecretPassword' and $salt= 'hsjYeg/bxn()%3jdhsGHq0'   aHNqWWVnL2J4bigpJTNqZGhzR0hxMA==$a9c810e9c722af719adabcf50d b8a0b4cd0d14e07eddbb43e5f47bde620a3c13 Green= salt, Red= encrypted password
  33. 33. scrypt ● http://www.tarsnap.com/scrypt.html ● scrypt is a sequential memory hard algorithm: ● memory-hard functions require high memory ● cannot be parallelized efficiently ● scrypt uses PBKDF2, HMAC-SHA256, Salsa 20/8 core
  34. 34. scrypt security “From a test executed on modern (2009) hardware, if 5 seconds are spent computing a derived key, the cost of a hardware brute-force attack against scrypt is roughly 4000 times greater than the cost of a similar attack against bcrypt (to find the same password), and 20000 times greater than a similar attack against Pbkdf2." Colin Percival (the author of scrypt algorithm)
  35. 35. Conclusion ● As user: Use only “robust” password (e.g. long pass phrase is better than a shorter random jumble of characters) Don't use the same password for different services ● As developer: Don't use hash or hash+salt to store a password! Use hash+salt+stretching (PBKDF2), bcrypt or scrypt to store your passwords
  36. 36. References ● Colin Percival, Stronger Key Derivation via Sequential Memory-Hard Functions, presented at BSDCan'09, May 2009 ● Morris, Robert, Thompson, Ken, Password Security: A Case History, Bell Laboratories, 2011 ● Coda Hale, How to safely store a password, 2010 http://codahale.com/how-to-safely-store-a-password/ ● J. Kelsey, B. Schneier, C. Hall, and D. Wagner, Secure Applications of Low-Entropy Keys, nformation Security Workshop (ISW'97), 1997 ● Marc Bevand, Whitepixel breaks 28.6 billion password/sec http://blog.zorinaq.com/?e=42 ● Andrew Zonenberg, Distributed Hash Cracker: A Cross- Platform GPU-Accelerated Password Recovery System, 2009
  37. 37. Thanks! Contacts: enrico@zimuel.it @ezimuel

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