Cryptography with Zend Framework

Cryptography in Zend Framework 2 Enrico Zimuel Senior PHP Engineer Zend Framework Team Zend TechnologiesUncon – 9th June, Dutch PHP Conference 2012

ZendCrypt● ZendCrypt is a new component of ZF2 (>= 2.0.0beta4)● Facilitates the usage of cryptography in PHP projects● Supports strong cryptography (standards + best practices)

ZendCrypt: main features● Symmetric encryption/decryption + authentication● Public key cryptography● Key Derivation Function (PBKDF2, Salted2SK)● Secure password hashing (bcrypt)● Hash● Hash-based Message Authentication Code (HMAC)

Supported algorithms● Mcrypt: AES (Rijndael-128), Rijndael-192/256, Blowfish, Twofish, DES, 3DES, CAST-128/256, Saferplus, Serpent,● OpenSSL: RSA, Diffie Hellman● PBKDF2, Salted2SK● Bcrypt● Hash/HMAC functions provided by PHP: MD5, SHA- 1/224/256/384/512, RIPEMD, TIGER, AVAL, ...

ZendCrypt components● ZendCryptSymmetricMcrypt● ZendCryptPublicKeyRsa● ZendCryptPublicKeyDiffieHellman● ZendCryptPassword● ZendCryptKeyDerivation● ZendCryptBlockCipher● ZendCryptHash● ZendCryptHmac

Encryption + authentication● ZendCryptBlockCipher● Default: – AES encryption in CBC mode – HMAC authentication (SHA-256) – Random IV for each encryption – PKCS7 padding (RFC 5652) – PBKDF2 for key derivation (encrypt and auth) – Prevent timing attacks

Example: encrypt/decryptuse ZendCryptBlockCipher;use ZendCryptBlockCipher; $cipher = BlockCipher::factory(mcrypt,$cipher = BlockCipher::factory(mcrypt, array(algorithm => aes) array(algorithm => aes)););$cipher->setKey(this is the encryption key);$cipher->setKey(this is the encryption key);$text$text = This is the message to encrypt; = This is the message to encrypt;$encrypted = $cipher->encrypt($text);$encrypted = $cipher->encrypt($text); printf("Encrypted text: %sn", $encrypted);printf("Encrypted text: %sn", $encrypted);$text$text = $cipher->decrypt($encrypted); = $cipher->decrypt($encrypted);printf("Decrypted text: %sn", $text);printf("Decrypted text: %sn", $text);

Encryption format Encryption = HMAC . IV . ENCRYPT● MSG is the message to encrypt● KEY is the encryption key (by PBKDF2)● AUTH is the authentication key (by PBKDF2)● ENCRYPT = AES(MSG, KEY)● HMAC = HMAC(sha256, AUTH, AES . IV . ENCRYPT)● IV = random

How to store a password?● “More than 6 million LinkedIn passwords stolen” 7th July 2012, cnnmoney.com● Dont use only an hash algorithm (dictionary attacks)● Even using a salt is insecure (brute force attacks)

How to safely store a password● bcrypt is an adaptive cryptographic hash function for passwords● Its considered secure because is slow (prevent dictionary attacks)● Implemented using crypt() of PHP● It uses a parameter, the workload (or cost) that specify the amount of work● More work means more secure hash value

Example: usage of bcrypt use ZendCryptPasswordBcrypt; use ZendCryptPasswordBcrypt; $bcrypt $bcrypt = new Bcrypt(); = new Bcrypt(); $password = $bcrypt->create(password); $password = $bcrypt->create(password); printf ("Password: %sn", $password); printf ("Password: %sn", $password);● The output ($password) is a string of 60 bytes● The default value of the working factor is 14

The bcrypt workload

Check for valid passwordsuse ZendCryptPasswordBcrypt;use ZendCryptPasswordBcrypt; $bcrypt$bcrypt = new Bcrypt(); = new Bcrypt();$password = $_POST[password];$password = $_POST[password];$hash$hash = …; // i.e. get from a database = …; // i.e. get from a databaseif ($bcrypt->verify($password, $hash)) {if ($bcrypt->verify($password, $hash)) { echo “The password is valid”; echo “The password is valid”;} else {} else { Echo “The password is not valid”; Echo “The password is not valid”;}}

Key Derivation Function● NEVER USE users password as crypto key!● Key Derivation Function generates cryptographic keys based on users passwords● PBKDF2 is a KDF (RFC 2898, PKCS #5 v2.0)

PBKDF2 “PBKDF2 applies a pseudorandom function, such as a cryptographic hash, cipher, or HMACto the input password or passphrase along witha 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. The added computational work makes password cracking much more difficult, and is known as key stretching” From Wikipedia

Example: Pbkdf2use ZendCryptKeyDerivationPbkdf2,use ZendCryptKeyDerivationPbkdf2, ZendMathMath; ZendMathMath; $salt = Math::randBytes(32);$salt = Math::randBytes(32);$pass = this is the password of the user;$pass = this is the password of the user;$hash = Pbkdf2::calc(sha256, $pass, $salt, 10000, 32);$hash = Pbkdf2::calc(sha256, $pass, $salt, 10000, 32);● It generates a crypto key of 32 bytes using SHA-256 + random salt with an interation of 10000 times

How many iterations we need?● It depends on the CPU power that you use● Suggestion: use at least 1 sec. of computation● Using an Intel Core i5 CPU at 3.3Ghz you need at least 100’000 iterations to get about 1 sec. of computation

ZF2 random number generator● ZendMathMath::randBytes($length, $strong = false)● ZendMathMath::rand($min, $max, $strong = false)● Fallback strategy: 1) If OpenSSL: openssl_random_pseudo_bytes() 2) If Mcrypt: mcrypt_create_iv() 3) If (!$strong): mt_rand() 4) else throwing exception “Cannot generate strong random numbers”

Some references● Niels Ferguson, Bruce Schneier, and Tadayoshi Kohno “ Cryptography Engineering” John Wiley & Sons, 2010● Dan Boneh, Cryptography Course, Stanford University, Coursera free online courses● Coda Hale, How to safely store a password● Zend Framework 2● Anthony Ferrara, PHP-CryptLib● E.Zimuel “Cryptography in PHP” Web & PHP Magazine, Issue 2/2012● E.Zimuel “Cryptography made easy with Zend Framework”

Thanks!● Contacts: enrico@zend.com @ezimuel

Cryptography with Zend Framework

by Enrico Zimuel on Jun 12, 2012

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