password (in)security
DESCRIPTION
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/moca2012TRANSCRIPT
Password (in)securityHow to generate and store passwords
in a secure way
by Enrico “cerin0” Zimuel
About me 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
1998
Password
A password is a secret word or string of characters that is used for
authentication.
User perspective:
How to choose a “secure” password?
Developer perspective:
How to store a password in a secure way?
Password security
Basically every security systemis based on password.
When security fails...
linkedin.com
Hack: 6th June 2012 More than 6 million passwords
was compromisedSHA1 password
eharmony.com
Hack: 6th June 2012 More than 1.5 million passwords
was compromisedSHA1 password
last.fm
Hack: 7th June 2012? million passwords was
compromisedMD5 password
yahoo.com
Hack: 12th June 2012 443K passwords was compromised
SQL injection, password in plaintext!
How to choose a “robust” user's password
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
http://howsecureismypassword.net/
Developers
Force the user to generate robust password
How to store a password in a secure way?
Developers
Old school (deprecated)
Use hash algorithms likeMD5 or SHA1
New school (deprecated?)
Use hash algorithm + salt(a random string).
Using hash + salt
Prevent dictionary attacks? YES Prevent brute force attacks? NO
Brute forcing attacks
CPU power is growing (multi-core)GPU are rendering password security uselessUse a Cloud system (n-CPU)
Brute forcing with a GPU
Source: www.nvidia.com
GPU and CUDA
CUDA™ is a parallel computing platform and programming model invented by NVIDIA
Extreme GPU Bruteforcerusing NVIDIA GTS250 ~ $100
Source: http://www.insidepro.com/eng/egb.shtml
Algorithm Speed 8 chars 9 chars 10 chars
md5($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)
IGHASHGPUATI HD 5970 ~ $700
Source: http://www.golubev.com/hashgpu.htm
Algorithm Speed 8 chars 9 chars 10 chars
md5($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)
Whitepixel4 Dual HD 5970~ $2800
Source: http://blog.zorinaq.com/?e=42
Algorithm Speed 8 chars 9 chars 10 chars
md5($pass) 33 billion p/s 1 ½ hour 4 ½ days 294 days
Password of 62 characters (a-z, A-Z, 0-9)
Secure algorithms forpassword storing
● Hash + salt + stretching (i.e. PBKDF2)● bcrypt● scrypt
Hash + salt + stretching
● Stretching = iterate (hash + salt) n-times
key = ““for 1 to ntimes do key = hash(key + password + salt)
How to estimate thenumber 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
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
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);
}
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)
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.
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 $salt= 'hsjYeg/bxn()%3jdhsGHq0' aHNqWWVnL2J4bigpJTNqZGhzR0hxMA==$a9c810e9c722af719adabcf50db8a0b4cd0d14e07eddbb43e5f47bde620a3c13
Green= salt, Red= encrypted password
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
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)
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
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, 2010http://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/sechttp://blog.zorinaq.com/?e=42
● Andrew Zonenberg, Distributed Hash Cracker: A Cross-Platform GPU-Accelerated Password Recovery System, 2009