Andy Watson, an employee of Ionic Security, gave a presentation on properly using cryptography in applications. The presentation covered topics such as random number generation, hashing, salting passwords, key derivation functions, symmetric encryption algorithms and common mistakes made with cryptography. The goal was to help people avoid vulnerabilities like unsalted hashes, hardcoded keys, weak random number generation and improper encryption modes.
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
https://www.random.org/randomness/
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. 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. 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. 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. 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. 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. 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 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. 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
● 64 bit random salt
● 5000 iterations of SHA1 (hashing function)
SCRYPT
● Consumes large amounts of memory on
purpose
22. PBKDF2 In A Nutshell™
Password
SALT +
Password
Prepend SALT
Intermediate
Hash
SHA1
REPEAT 5000
TIMES
Final Hash
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
https://crackstation.net/hashing-security.htm
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
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
28. Comparing ECB to other modes
http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
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
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. Which is bad because...
A lot of people use the same password
everywhere and use their email address as
their login!
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. 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
38.
39. Beware The Default Settings
Default settings for Android Bouncy Castle
starting in 2.1 were horribly unsafe
Defaulted to ECB mode!
40. 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
41. 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!)
42. UnSalted Hashes
In 2012, LinkedIn password hashes were
stolen.
They were not salted.
60% of them were cracked.
43. Crisis Averted at Slack
User profile data stolen in February 2015
Passwords hashed with bcrypt and random
salts
44. 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
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.