Slides for a talk I gave on 2/9/13 at Sunshine PHP in Miami.

1. Cryptography
In PHP
For The Average Developer

2. Cryptography
● Keeping Data Secure
○ Safe From Viewing
○ Safe From Tampering
○ Safe From Forgery
● Not A Silver Bullet
○ XSS
○ SQLI
○ Social Engineering
● Very Hard To Do
○ Any bug will cause problems

3. The First Rule
of Cryptography

4. Don't Do It!

5. Leave It
For
Experts

6. Random!
The Foundation of Cryptography
● Classified Under Three Types:
○ Weak
■ For non-cryptographic usages
○ Strong
■ For cryptographic usages where security does
not depend on the strength of randomness
○ Cryptographically Secure
■ For cryptographic usage when security does
depend on the strength of randomness

7. Vulnerabilities of
Randomness
● Bias
○ Certain values tend to occur more often making it
easier to predict future numbers
● Predictability
○ Knowing past numbers helps predict future
numbers
● Poisoning
○ Ability to alter future random number generation

8. Weak Random in PHP
Not to be used for cryptographic usages!!!
● rand()
● mt_rand()
● uniqid()
● lcg_value()

9. Strong Random in PHP
● mcrypt_create_iv()
○ MCRYPT_DEV_URANDOM
● openssl_random_pseudo_bytes()
● /dev/urandom
○ For *nix systems only

10. Cryptographically Secure
● mcrypt_create_iv()
○ MCRYPT_DEV_RANDOM
● openssl_random_pseudo_bytes()
○ Maybe
● /dev/random
○ For *nix systems only

11. NEVER
Use Weak
For Security

12. NEVER
Use CS
When Not
Needed

13. If In Doubt
Use Strong
Randomness

14. Encryption vs Hashing
● Encryption
○ Encoding
○ 2 Way / Reversible
○ Putting a lock on a box

16. Encryption vs Hashing
● Encryption
○ Encoding
○ 2 Way / Reversible
○ Putting a lock on a box
● Hashing
○ Signing
○ 1 Way / Non-Reversible
○ Taking a person's finger-print

18. Encryption

19. Seriously,
Don't Do It!

20. Terms
● Key
○ Secure string of data
● Plain-Text
○ The text you want to keep secret
● Cipher-Text
○ The encrypted output

21. Two Basic Types
● Symmetric Encryption
○ Like a Pad-Lock with a shared key
○ The only secret is the key
○ Both sides must have the same key

23. Two Basic Types
● Symmetric Encryption
○ Like a Pad-Lock with a shared key
○ The only secret is the key
○ Both sides must have the same key
● Asymmetric Encryption
○ Like a pair of Pad-Locks
■ The "lock" is the public key
○ The only secret is the private key
○ Both sides have their own key

25. Symmetric Encryption 101
● Number:
01
Scratch That
● Numbers:
01 04 01 54 95 42 64 12

26. Symmetric Encryption 101
Let's Add A "Secret" Number!
01 04 01 54 95 42 64 12
+10
11 14 11 64 05 52 74 22

28. Secret Numbers
● We just invented the Caesar Cipher
○ Commonly known as "ROT13"
● But There Are Problems:
○ Vulnerable To Statistical Attacks
○ Vulnerable To Brute Forcing
■ Only 100 possible secret numbers!

29. Symmetric Encryption 101
I Know: Let's Add A Different Number!
01 04 01 54 95 42 64 12
+10 43 21 95 42 67 31 83
11 47 22 49 37 09 95 95

30. How It Works
We can generate the pads in two ways
● Randomly
○ If we only use once, perfect security
■ Known as a one-time-pad
○ If we use multiple times, same as caesar
cipher
● With A Function
○ Give one or two inputs
■ A key, and an "input"
○ Generates a "stream" of pseudo random
numbers

31. Ciphers
● Take 2 inputs
○ A secret key
○ An "input"
● Produces Pseudo-Random Output
○ Looks random (statistically)
○ Is deterministic
■ Reproducible given same inputs

32. Modes
● Multiple ways to use the keystream
● Each way is known as a "Mode"
● Some are secure
○ Others are not

33. ECB
Electronic Code Book
● Uses plain-text as "input"
● Uses output as cipher-text
● VERY BROKEN!!!

34. ECB

35. CBC
Cipher Block Chaining
● Uses an "Initialization Vector"
○ Helps "randomize" the plain-text
○ Ensures no non-unique blocks
○ Does NOT need to be secret
● Chains each block together
○ Propagating the generated "randomness"
● Plain-Text Must Be Padded
○ To a multiple of block-size
● Secure!

36. CBC

37. CFB
Cipher FeedBack
● Uses an "Initialization Vector"
● Plain-Text never enters cipher
○ Does not need to be padded
● "Decrypt" Is Never Used
● Secure!

38. CFB

39. Ciphers
● AES 128 & 256
○ Standard
■ NIST Approved
○ Also Known As RIJNDAEL-128
■ 128 here refers to "block size"
○ Very Strong
○ Note, the number after AES is *key size*
● Blowfish
● TwoFish
● Serpent

40. Authentication
How do you know it wasn't tampered
with / came from your friend?
● HMAC
○ Hash-based Message Authentication Code
● USE A SEPARATE KEY!
● Encrypt-Then-MAC
○ Always MAC after encryption

41. All Together
Now!

42. Encrypt
$key = 'xxxxxxxxxxxxxxxx';
$authKey = 'XXXXXXXXXXXXXX';
$plain = 'This is plain text that I am going to encrypt';
$size = mcrypt_get_iv_size(
MCRYPT_RIJNDAEL_128,
MCRYPT_MODE_CFB
);
$iv = mcrypt_create_iv(
$size,
MCRYPT_DEV_URANDOM
);
$cipherText = mcrypt_encrypt(
MCRYPT_RIJNDAEL_128,
$key,
$plain,
MCRYPT_MODE_CFB,
$iv
);
$auth = hash_hmac('sha512', $cipherText, $authKey, true);
$encrypted = base64_encode($iv . $cipherText . $auth);

43. Decrypt
$key = 'xxxxxxxxxxxxxxxx';
$authKey = 'XXXXXXXXXXXXXX';
$size = mcrypt_get_iv_size(
MCRYPT_RIJNDAEL_128,
MCRYPT_MODE_CFB
);
$encrypted = base64_decode($encrypted);
$iv = substr($encrypted, 0, $size);
$auth = substr($encrypted, -64);
$cipherText = substr($encrypted, $size, -64);
if ($auth != hash_hmac('sha512', $cipherText, $authKey, true)) {
// Auth Failed!!!
return false;
}
$plainText = mcrypt_decrypt(
MCRYPT_RIJNDAEL_128,
$key,
$cipherText,
MCRYPT_MODE_CFB,
$iv
);

44. Please Don't Do It!
● Notice How Much Code It Took
○ Without error checking
● Notice How Complex It Is
○ Without flexibility
● Notice How Easy To Screw Up
○ Without Key Storage
● Notice How Many Decisions To Make

45. If you MUST,
Use a Library

46. Common Encryption Needs
● Between Client / Server
○ Use SSL
○ Really, just use SSL
○ I'm not kidding, just use SSL
● Storage
○ Use disk encryption
○ Use database encryption

47. Really,
Don't Do It!

48. Encryption Resources
● Zend Framework Encryption
○ Very good and complete lib
○ ZF2
■ ZendCryptBlockCipher
● PHP Sec Lib
○ phpseclib.sourceforge.net
○ Pure PHP
● Not Many Others
○ Beware of online tutorials!!!

49. Learn More
● Coursera <-- FREE!!!
○ Cryptography 1
○ Cryptography 2

50. Password
Storage

51. Passwords
Should Be
HASHED!
Not Encrypted!

52. Password Hashes
● Use A Salt
○ Defeats Rainbow Tables
○ Makes Each Hash a "Proof Of Work"
○ Should be random!
■ Strong Randomness
● Should Be SLOW!
○ Salt is not enough

55. Brute Forcing
25 GPU Cluster
- md5: 180 Billion per second
- < $50,000
6 char passwords: 4 seconds
7 char passwords: 6 minutes
8 char passwords: 10 hours
Entire English Language: microseconds
"LEET" Permutations: 0.7 seconds

56. Good Algorithms
crypt($password, $salt);
pbkdf2($password, $salt, $i);
password_hash(
$password,
PASSWORD_BCRYPT
);
$passLib->hash($password);
$phpass->hashPassword($pass);

57. Cost Parameter
● Target: 0.25 - 0.5 Seconds
○ As slow as you can afford
● Depends on hardware
○ Test it!
● Good Defaults:
○ BCrypt: 10
○ PBKDF2: 10,000

58. Simplified
Password
Hashing

59. New API for 5.5
● string password_hash($pass, $algo, array $options =
array() )
○ Generates Salt, hashes password
● bool password_verify($pass, $hash)
○ Verifies Hash with Password
● bool password_needs_rehash($hash, $algo, array $options = array())
○ Determines if the hash is the same as
specified by algo and options
● array password_get_info($hash)
○ Returns information about the hash

60. Example
function register($user, $password) {
$hash = password_hash($password, PASSWORD_BCRYPT);
$this->store($user, $hash);
}
function login($user, $password) {
$hash = $this->fetchHash($user);
if (password_verify($password, $hash)) {
if (password_needs_rehahs($hash, PASSWORD_BCRYPT)) {
$hash = password_hash($password, PASSWORD_BCRYPT);
$this->store($user, $hash);
}
$this->startSession();
return true;
}
return false;
}

61. Hashing Resources
● PHP 5.5 API
○ wiki.php.net/rfc/password_hash
○ php.net/password
● Password Compat
○ PHP 5.5 Compatibility
○ github/ircmaxell/password_compat
● PasswordLib
○ 5.3+, Multiple Algorithms, Portable
○ github/ircmaxell/PHP-PasswordLib
● PHPASS
○ PHP 4+
○ openwall.com/phpass

62. Seriously,
Hire an Expert!

63. You Have Been
Warned

64. Anthony Ferrara
joind.in/8027
@ircmaxell
blog.ircmaxell.com
me@ircmaxell.com
youtube.com/ircmaxell