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Using Cryptography Properly in Applications


Published on

Andy Watson
Lead Developer
Ionic Security

Great Wide Open 2016
Atlanta, GA
March 16th, 2016

Published in: Technology
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Using Cryptography Properly in Applications

  1. 1. Using Cryptography Properly in Applications Andy Watson Ionic Security #GWOCryptoParty Great Wide Open 2016
  2. 2. About: Name: Andy Watson Occupation: Byte Mangler Employer: Ionic Security
  3. 3. Why am I here? I’ve seen too many people not using cryptography or using it incorrectly. This information may help you not be one of them.
  4. 4. Agenda: ● Random ● Salt ● Hash ● Key Derivation ● Symmetric Encryption ● Famous Mistakes
  5. 5. Random
  6. 6. Random Number Generators RNG: A computational or physical device designed to generate a sequence of numbers that lack any pattern True random number generators depend on an entropy source like radioactive decay or radio frequency noise For cryptographic functions, higher levels of entropy are required to work properly
  7. 7. Pseudo Computational RNG are known as Pseudo RNG PRNG are “seeded” with a value to generate a series of numbers
  8. 8. Hashes
  9. 9. HASH!
  10. 10. Hashing Function (n.) A Function that represents data of arbitrary size as data of a fixed size. $ echo "Great Wide Open 2016" | md5 e2be8adfadee4bfe635041c4c37dadac $ echo "All Things Open 2015 " | md5 402854038fbffe281a518b53cdbd5594
  11. 11. When to Hash Use hashing functions when saving the original data would be a liability you have no business dealing with For Example: Linux Passwords $6$pWVzxN/iFRstrZ/.$TNBvzXhc8b9SBkl1q36YNvF2Dwu S4/7LsICepYgaWCKzM1MS.OBK5TvxrUQ4.I5x5NtqidhBTG obQLOqxBAFe1
  12. 12. Don’t Store The Clear Credentials should be hashed when stored During login, hash the password entered and check it against the hash you saved
  13. 13. When Hashes Collide These two blocks have the same md5 hash of 79054025255fb1a26e4bc422aef54eb4 d131dd02c5e6eec4693d9a0698aff95c 2fcab58712467eab4004583eb8fb7f89 55ad340609f4b30283e488832571415a 085125e8f7cdc99fd91dbdf280373c5b d8823e3156348f5bae6dacd436c919c6 dd53e2b487da03fd02396306d248cda0 e99f33420f577ee8ce54b67080a80d1e c69821bcb6a8839396f9652b6ff72a70 d131dd02c5e6eec4693d9a0698aff95c 2fcab50712467eab4004583eb8fb7f89 55ad340609f4b30283e4888325f1415a 085125e8f7cdc99fd91dbd7280373c5b d8823e3156348f5bae6dacd436c919c6 dd53e23487da03fd02396306d248cda0 e99f33420f577ee8ce54b67080280d1e c69821bcb6a8839396f965ab6ff72a70
  14. 14. You. Must. Hash. Securely. Cryptographically Secure Hash Function (n.) A hash function which is infeasible to reverse back to the original message and not subject to collisions $ echo "Great Wide Open 2016" | shasum -a 51240094ad14fec6107ccabbc430e00cb9ef34f75a45420ca055eb294ccbcc8f 2084da4ec10f852c4e6cc372d2f3f7ab34fbfc113661b2735243621509ef9b3d 3dd
  15. 15. Taste the Rainbow Table A rainbow table is a precomputed table for reversing cryptographic hash functions, usually for cracking password hashes. Password MD5 Hash 123456 e10adc3949ba59abbe56e057f20f883e password 5f4dcc3b5aa765d61d8327deb882cf99
  16. 16. It’s not just for your fries SALT
  17. 17. What is a Salt? Random data added to your input to create better output from one way functions Useful for defending against dictionary and rainbow table attacks. $ echo "secret" | md5 Dd02c7c2232759874e1c205587017bed $ openssl rand -hex 16 72f72e199d1292317ee60cbe3c50b5ba $ echo "72f72e199d1292317ee60cbe3c50b5ba secret" | md5 7cb940bf5166c52834a9e831a6299091
  18. 18. Key Derivation
  19. 19. Key Derivation Functions KDF create new secret keys from a secret value and a known value - like a password Key Derivation Functions can be used in a “key stretching” routing to enhance hashing functions to provide much more protection from rainbow tables and brute force attacks
  20. 20. Original KDF: crypt ● Invented in 1978 to protect UNIX passwords ● Used only a 12 bit salt ● Limited passwords to 8 characters
  21. 21. Modern KDFs PDKDF2 ● 64 bit random salt ● 5000 iterations of SHA1 (hashing function) SCRYPT ● Consumes large amounts of memory on purpose
  22. 22. PBKDF2 In A Nutshell™ Password SALT + Password Prepend SALT Intermediate Hash SHA1 REPEAT 5000 TIMES Final Hash
  23. 23. Save the Salt Store the salt, the resulting hash and the number of iterations in your data store You’ll have to calculate the derived key of the credential again to verify it is correct
  24. 24. Vulnerabilities • ASICs exists that can run PBKDF2 processes very quickly • bcrypt requires the use of more memory so it makes it harder to implement in silicon • scrypt is more modern and can be tuned to use even more memory
  25. 25. Symmetric Encryption
  26. 26. Symmetric Encryption Used when your application needs to protect data at rest (on disk etc) but will need to use those values later The most common algorithm for symmetric encryption is AES (Advanced Encryption Standard) It can operate in multiple modes like ECB, CBC, CTR and GCM - each suited to different uses
  27. 27. ECB Mode Electronic Code Book Simplest mode: Operates on blocks of plaintext
  28. 28. Comparing ECB to other modes
  29. 29. Galois Counter Mode (GCM) Encrypts and Authenticates Messages Reduces the opportunity for interference with messages to go undetected Functions at a high rate of speed Became NIST standard in 2007
  30. 30. Simple!
  31. 31. Uses of GCM • TLS 1.2 • SSH • IPsec
  32. 32. Let’s talk about it. Mistakes Were Made
  33. 33. The Stupid. It Hurts.
  34. 34. Le Sigh. My password is stored in their database in plaintext. It was not hashed or they could not have emailed it to me! Obviously, the password I use with them is a special snowflake.
  35. 35. Which is bad because... A lot of people use the same password everywhere and use their email address as their login!
  36. 36. So... An attacker that gets this password list can try to log in to all kinds of things as you! 1. email 2. banks 3. credit reporting 4. even NetFlix!
  37. 37. Adobe Hack Millions of “encrypted” passwords stolen Hashed with MD5 Large numbers of them found in rainbow tables Most Common Password: 123456
  38. 38. Beware The Default Settings Default settings for Android Bouncy Castle starting in 2.1 were horribly unsafe Defaulted to ECB mode!
  39. 39. Empirical Study of Android Apps 11,748 applications analyzed 5,656 used ECB mode by default 3,644 used a constant symmetric key 2,000 used ECB mode ON PURPOSE! 1,932 used a constant IV 1,629 seeded PRNG with static value
  40. 40. Seeding the PRNG In 2006 a bug in Debian and Ubuntu caused the PID to be used as the output of the PRNG - only 32,768 possible values! (hint: that’s not enough!)
  41. 41. UnSalted Hashes In 2012, LinkedIn password hashes were stolen. They were not salted. 60% of them were cracked.
  42. 42. Crisis Averted at Slack User profile data stolen in February 2015 Passwords hashed with bcrypt and random salts
  43. 43. Unlocking Your Prius System uses rotating codes in a small range Some built in (pre-shared) keys for repair use No protection from replaying codes Brute force attacks possible
  44. 44. Scared yet?
  45. 45. @andrewwatson Thank You