Cryptography for the mere mortals - for phpXperts Seminar 2011 by Hasin and Tonu
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Cryptography for the mere mortals - for phpXperts Seminar 2011 by Hasin and Tonu
- 8. julius caesar : caesar cipher key = 3
- 9. julius caesar : caesar cipher key = 3 hasin = kdvlq
- 10. rise of the machines
- 11. cryptography in bangla way
- 12. !@#$%^&* The science of writing in secret code
- 13. daily cryptography SSL Session/Cookie Encryption Storing Sensitive Information Secure Message Transportation Signing Documents
- 14. terms Plaintext Key Cipher Encryption Ciphertext Decryption
- 15. techniques Symmetric Cryptography = shared secret key Asymmetric Cryptography = public key + private key Hash Cryptography = One way
- 16. cryptography in PHP cracklib hash mCrypt openSSL mHash
- 17. one way journey md5 sha1 Sha2 Sha 256 Sha 512
- 18. problems of MD5/SHA1 Collision Attack hash(data1) = hash(data2)
- 19. why salt?
- 20. password! Use a salt value in hash functions or bcrypt hash( $salt . $password ); hash_hmac( ‘sha512’, $salt . $password ); crypt($password , $salt );
- 21. symmetric encryption One single key Shared between parties Popular
- 22. sample encryption - AES… $ivlength = mcrypt_get_iv_size( MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC); $iv = mcrypt_create_iv( $ivlength, MCRYPT_RAND);
- 23. sample encryption - AES $encryptedText = mcrypt_encrypt( MCRYPT_RIJNDAEL_256, $key, $data, MCRYPT_MODE_CBC, $iv);
- 24. sample decryption – AES $decryptedText = mcrypt_decrypt( MCRYPT_RIJNDAEL_256, $key, $encryptedText, MCRYPT_MODE_CBC, $iv);
- 25. asymmetric encryption public / private key semi-shared
- 26. meet with bob and alice
- 27. bob and alice’s story Bob Asks Alice For her public key Bob signs msg with the public key of Alice Alice gets encrypted msg Alice decrypts msg with her secret private key Alice reads It
- 28. public/private key encryption RSA openSSL
- 29. RSA key-pair ssh-keygen –t RSA –b <bit> Generating public/private rsa key pair. Enter file in which to save the key (/Users/hasinhayder/.ssh/id_rsa): /tmp/pk_rsa Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /tmp/pk_rsa Your public key has been saved in /tmp/pk_rsa.pub
- 30. RSA key to PEM format openssl rsa -in pk_rsa -outform pem > pk_rsa.pem
- 31. generate RSA key in PEM format openssl genrsa -des3 -out pk_rsa.pem 2048
- 32. public key out of PEM file openssl rsa -pubout -in pk_rsa.pem -out pk_pub.pem
- 33. encrypt with public key $pub_key=openssl_get_publickey( file_get_contents("/tmp/pk_pub.pem")); openssl_public_encrypt( $source, $crypttext, $pub_key);
- 34. decrypt using private key… $passphrase = “<secret passphrase>"; $key = openssl_get_privatekey( file_get_contents("/tmp/pk.pem"), $passphrase);
- 35. decrypt using private key openssl_private_decrypt( $crypttext, $plaintext, $res);
- 36. there are always some bad guys…
- 37. best practices PCI DSS Compliance
- 38. best practices AES (RIJNDAEL) BLOWFISH TWOFISH SHA-256, 384, 512 RSA
- 40. key space Secret key space >= 128 bit Public key space >= 2048 bit
- 41. thanks M A Hossain Tonu Sr. Software Engineer, somewherein… http://mahtonu.wordpress.com Hasin Hayder Founder, Leevio http://hasin.wordpress.com
Notes de l'éditeur
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- Plaintext The initial unencrypted (unscrambled) data to be communicated. CiphertextPlaintext is encrypted (scrambled) into something unintelligible – ciphertext for communication Example: “esqbsuibqsbujnebt” Encryption The process of converting ordinary information ( plaintext ) into ciphertext . Decryption The reverse process of moving from unintelligible ciphertext to plaintext . Cipher Pair of algorithms performing encryption & decryption. Key A secret parameter for the cipher algorithm. Key Management Management of generation, exchange, storage, safeguarding, use, vetting, and replacement of keys. Provisions in Cryptosystem design, Cryptographic protocols in that design, User procedures, and so on. Crypto Analysis / Code Breaking The study of how to circumvent the confidentiality sought by using encryption.
- To check if a given $password string is valid, for a given hash, you can use the following condition:If($hash==crypt($password,$hash)) echo ‘valid’;
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- rand() predictablea cryptographically strong random number in PHP you have to use the function openssl_random_pseudo_bytes() of the OpenSSL library, available at PHP 5.3
- DES cipher uses 56-bit key, that means the key space is 2^56.