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How to Use Cryptography Properly: The Common Mistakes People Make When Using Cryptographic Functions
The document discusses the proper use of cryptography in applications, focusing on key concepts such as random number generation, salting, hashing, key derivation, and symmetric encryption. It highlights common mistakes made in the implementation of cryptographic techniques, emphasizing the importance of securing passwords and the dangers of weak configurations. The speaker, Andy Watson from Ionic Security, aims to educate developers to avoid these pitfalls and use established methodologies to protect sensitive data.
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Similar to How to Use Cryptography Properly: The Common Mistakes People Make When Using Cryptographic Functions
How to Use Cryptography Properly: The Common Mistakes People Make When Using Cryptographic Functions
- 1. Using Cryptography Properly inApplications POSSCON 2015 Andy Watson Ionic Security
- 2. About: Name: Andy Watson Occupation:Byte Mangler Employer: Ionic Security http://ionicsecurity.com/
- 3. Why: I’ve seen toomany people not using cryptography or using it incorrectly. This information may help you not be one of them.
- 4. Agenda: ● Random ● Salt ●Hash ● Key Derivation ● Symmetric Encryption ● Famous Mistakes
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- 6. Random Number Generators RNG:A computational or physical device designed to generate a sequence of numbers that lack any pattern High quality 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. Pseudo Computational RNG areknown as Pseudo RNG PRNG are “seeded” with a value to generate a series of numbers
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- 9. What is aSalt? Random data added to your input to create better output from one way functions Useful for defending against dictionary and rainbow table attacks.
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- 12. Hashing Function (n.) AFunction that represents data of arbitrary size as data of a fixed size. $ echo 'Hello POSSCON 2015!' | md5 81ad0b0ba5f98e0f584c1cd9a2c324a3 $ echo 'Hello POSSCON 2015' | md5 0c9c470f340aedaba625908939ba3c7b
- 13. When to Hash Usehashing functions when saving the original data would be a liability you have no business dealing with For Example: Linux Passwords $6$pWVzxN/iFRstrZ/.$TNBvzXhc8b9SBkl1q36YNvF2DwuS 4/7LsICepYgaWCKzM1MS.OBK5TvxrUQ4. I5x5NtqidhBTGobQLOqxBAFe1
- 14. Don’t Store TheClear Credentials should be salted and hashed when stored During login, salt and hash the password entered and check it against the result you stored
- 15. When Hashes Collide Thesetwo blocks have the same md5 hash of 79054025255fb1a26e4bc422aef54eb4 This is called a collision d131dd02c5e6eec4693d9a0698aff95c 2fcab58712467eab4004583eb8fb7f89 55ad340609f4b30283e488832571415a 085125e8f7cdc99fd91dbdf280373c5b d8823e3156348f5bae6dacd436c919c6 dd53e2b487da03fd02396306d248cda0 e99f33420f577ee8ce54b67080a80d1e c69821bcb6a8839396f9652b6ff72a70 d131dd02c5e6eec4693d9a0698aff95c 2fcab50712467eab4004583eb8fb7f89 55ad340609f4b30283e4888325f1415a 085125e8f7cdc99fd91dbd7280373c5b d8823e3156348f5bae6dacd436c919c6 dd53e23487da03fd02396306d248cda0 e99f33420f577ee8ce54b67080280d1e c69821bcb6a8839396f965ab6ff72a70
- 16. Taste the RainbowTable A rainbow table is a precomputed table for reversing cryptographic hash functions, usually for cracking password hashes. Password MD5 Hash 123456 e10adc3949ba59abbe56e057f20f883e password 5f4dcc3b5aa765d61d8327deb882cf99
- 17. 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 "hello POSSCON 2015" | shasum -a 512 0d294c5140972735a80131eca426da4838cf5de1b3eb1c8cb51c4bb24823e389 d22a36be76be597a5c5a934dd5fada8b75e0986fb6e89329a820c22d96c4be17
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- 19. Key Derivation Functions KDFcreate 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. Original KDF: crypt ●Invented in 1978 to protect UNIX passwords ● Used only a 12 bit salt ● Limited passwords to 8 characters
- 21. Modern KDFs PDKDF2 ● 64bit random salt ● 5000 iterations of SHA1 (hashing function) SCRYPT ● Consumes large amounts of memory on purpose
- 22. PBKDF2 In ANutshell™ Password SALT + Password Prepend SALT Intermediate Hash SHA1 REPEAT SHA1 5000 TIMES Final Hash
- 23. Save the Salt Storethe salt, the resulting hash and the number of iterations in your datastore You’ll have to calculate the derived key of the credential again to verify it is correct
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- 25. Symmetric Encryption Used whenyour 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
- 26. ECB Mode Electronic CodeBook Operates on blocks of plaintext
- 27. Comparing ECB toother modes http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
- 28. Galois Counter Mode(GCM) Authenticates and Encrypts Messages Reduces the opportunity for interference with messages to go undetected
- 29. It’s Complicated Use awell known, well tested cryptographic library / framework - do not write your own! Do research before shipping your code - make sure you’re using the right primitives / modes for your application
- 30. Let’s point andlaugh Some Mistakes Were Made
- 31. The Stupid. ItHurts.
- 32. Le Sigh. My passwordis stored in their database. It was not hashed or they could not have emailed it to me!
- 33. Which is badbecause... A lot of people use the same password everywhere and use their email address as their login!
- 34. So... An attacker thatgets 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!
- 35. Adobe Hack Millions of“encrypted” passwords stolen Hashed with MD5 Large numbers of them found in rainbow tables Most Common Password: 123456 http://stricture-group.com/files/adobe-top100.txt
- 37. Beware The DefaultSettings Default settings for Android Bouncy Castle starting in 2.1 were not good Defaulted to ECB mode!
- 38. Empirical Study ofAndroid Apps 11,748 applications analyzed 5,656 used ECB mode by default 3,644 used a constant symmetric key 2,000 used ECB mode EXPLICITLY! 1,932 used a constant IV 1,629 seeded PRNG with static value
- 39. Seeding the Pseudo In2006 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!)
- 40. UnSalted Hashes In 2012,LinkedIn password hashes were stolen They were not salted so 60% of them were cracked
- 41. Crisis Averted atSlack User profile data stolen in February 2015 Passwords hashed with bcrypt and random salts Change your password anyway...
- 42. Unlocking Your Prius Systemuses rotating codes in a small range Some built in (pre-shared) keys for repair use No protection from replaying codes Brute force attacks possible Still under investigation...
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- 44. More Resources ForYou https://bitly.com/bundles/andrewwatson/2
- 45.