How to Use Cryptography Properly: Common Mistakes People Make When Using Cryptographic Functions
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Andy Watson Ionic Security - Lead Developer Monday, Oct 19th 3:25 pm - Security
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How to Use Cryptography Properly: Common Mistakes People Make When Using Cryptographic Functions
- 1. Using Cryptography Properly in Applications Andy Watson Ionic Security #ATOCrypto All Things Open 2015
- 2. About: Name: Andy Watson Occupation: Byte Mangler Employer: Ionic Security http://ionic.com/
- 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. Agenda: ● Random ● Salt ● Hash ● Key Derivation ● Symmetric Encryption ● Famous Mistakes
- 5. Random
- 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 are known as Pseudo RNG PRNG are “seeded” with a value to generate a series of numbers
- 8. Crossing the Streams Combining weak streams of randomness together through an XOR operation produces better randomness.
- 9. Hash
- 10. HASH!
- 11. Hashing Function (n.) A Function that represents data of arbitrary size as data of a fixed size. $ echo "All Things Open 2015" | md5 B223144b809550c8a7e3129a18728eef $ echo "All Things Open 2015 " | md5 402854038fbffe281a518b53cdbd5594
- 12. 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
- 13. Don’t Store The Clear Credentials should be hashed when stored During login, hash the password entered and check it against the hash you stored
- 14. 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
- 15. 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 "All Things Open 2015" | shasum -a 512 d9d2cdfdece786ecb10e0a9a95dc0e95fab23485a682f890be8a272679482a4b 982a6e45576857788687d064b75203f2b8f7ef0eb6be3f559a4cada697ac3808
- 16. 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
- 17. It’s not just for your fries SALT
- 18. 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
- 19. Key Derivation
- 20. 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
- 21. Original KDF: crypt ● Invented in 1978 to protect UNIX passwords ● Used only a 12 bit salt ● Limited passwords to 8 characters
- 22. Modern KDFs PDKDF2 ● 64 bit random salt ● 5000 iterations of SHA1 (hashing function) SCRYPT ● Consumes large amounts of memory on purpose
- 23. PBKDF2 In A Nutshell™ Password SALT + Password Prepend SALT Intermediate Hash SHA1 REPEAT 5000 TIMES Final Hash
- 24. Save the Salt Store the 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
- 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. ECB Mode Electronic Code Book Operates on blocks of plaintext
- 28. Comparing ECB to other modes http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
- 29. Galois Counter Mode (GCM) Authenticates and Encrypts Messages Reduces the opportunity for interference with messages to go undetected
- 30. Let’s talk about it. Mistakes Were Made
- 31. The Stupid. It Hurts.
- 32. 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.
- 33. Which is bad because... A lot of people use the same password everywhere and use their email address as their login!
- 34. 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!
- 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 Default Settings Default settings for Android Bouncy Castle starting in 2.1 were horribly unsafe Defaulted to ECB mode!
- 38. 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
- 39. 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!)
- 40. UnSalted Hashes In 2012, LinkedIn password hashes were stolen. They were not salted. 60% of them were cracked.
- 41. Crisis Averted at Slack User profile data stolen in February 2015 Passwords hashed with bcrypt and random salts
- 42. 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
- 43. Scared yet?
Editor's Notes
- Hello everyone, thank you for coming. I’m Andy Watson and I’m here to talk to you about ways to use cryptography correctly in your applications
- I’m currently a senior engineer at Ionic Security which is a data protection security company based out of Atlanta, GA I’ve been a software developer professionally since 1996 when I got my first job developing large scale, distributed systems for processing streams of data collected out of particle accelerators with some Physics professors at FSU. This was “cloud” computing before it had a name. Since then I’ve built mobile, desktop and web applications for companies like The Walt Disney World Resort, Maersk Sealand, Cox Communications, CoffeeCup Software and many many others.
- So why am I up here today? Simply put, a lot of people do cryptography terribly - if they even attempt it. This means that when the people using those applications enter data into them it’s vulnerable to theft and loss. I’ll show some terrible examples of this later.
- fuck, that looks delicious.
- Back in the old days, a lot of applications would simply md5() your password and store that in their database. Some still do this. Some don’t do anything! More on that later… So what
- Collisions like this are rare but they can happen. This means that MD5 is not suitable for any cryptographic operations, especially things like verifying the authenticity of TLS certificates.
- To protect sensitive information like passwords, you should use a derivation function that repeats a hashing process thousands of times to produce unique and irreversible hashes
- the first key derivation function was created almost 40 years ago but it had significant weaknesses.
- More modern derivation functions are much better at protecting information because they use better hashes and perform them thousands of times. Another variation of PBKDF2 would be to use 1000 iterations of SHA-256 instead of SHA-1
- So what if you need to protect something that you have to get back in its original form? That’s where symmetric encryption is used.