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IMPROVING YOUR PASSWORD WITH SALT
Tayler AngevineBachelor of Arts in Computer ScienceDr. Ken Blaha (Advisor)May 03, 2014
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INTRODUCTION Why did I choose this project? Design of original project
How my project turned into what it is now Two-way Symmetric Encryption Key Generation and Storage Salting How does a hashing algorithm work: SHA-256 Why is SHA-256 widely used Demonstration Conclusion Questions
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“Hardly a week goes by without a major password breach at one website or another—in one week, nearly 500,000 Yahoo passwords were exposed, Formspring's server hack gave up nearly as many passwords, and Nvidia's developer zone was breached. And that's just some of the hacks we heard about...”
• Neil J. Rubenking (pcmag)
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ORIGINAL PROJECT Password Management Application
Desktop Application Use a password to log in (a username was not
required) A central place to store all of your usernames
and passwords “a place to keep all of your keys”
Why was this useful? Emphasis on security caused me to keep
forgetting passwords. Tired of resetting password and calling customer
service
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REQUIREMENTS 100% reliable
Should be able to open the program and retrieve information whenever needed.
Completely Secure
Trust is a reoccurring theme when it comes to password management applications.
How does one safely store passwords? Incorrect and Correct Techniques Creating a safe environment for your information
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WHAT IS CRYPTOGRAPHY? Secret writing
The computerized encoding and decoding of information Symmetric-key cryptography Hashing
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COMPROMISED DATABASES “Hardly a week goes by without a major
password breach at one website or another—in one week, nearly 500,000 Yahoo passwords were exposed…”
Focal point of my project
Everything should be encrypted in the database
Which algorithms can encrypt and decrypt information? Information needed to be encrypted, but returned to
plaintext
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ADVANCED ENCRYPTION STANDARD (AES) Two-way symmetric encryption algorithm.
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WHAT IS THE KEY USED FOR? A key is a string that is used to shift each
letter by a number of places or something much more complicated. Operations: XOR, bit shifts, etc.
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KEY DERIVATION Key must be a certain length
128, 192, 256 bits Bigger the key means more key rounds.
10, 12, 14 Key rounds refer to repetitions of AES operations (shift rows, mix
columns, add round key)
If you use a password as a key you must take some precautionary steps Passwords tend to be weak Key should be hashed first using sha 256 Ciphered using AES with a randomly generated Key. (Key used
should be stored) Ensure “randomness”
Hashed again using sha 256. Key size
Prevent from Dictionary Attacks
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KEY DERIVATION CONTINUED… Plenty of Libraries for creating secret keys
Java’s SecretKeyFactory SecretKey
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STORING THE KEY Key must be stored in order to encrypt and
decrypt data. Problem that’s been around for years
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STORING KEY IN DATABASE Common Solution
Risky
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STORING KEY IN SEPARATE FILE Common Solution
Risky Anything done in code can be undone. Humans are predictable
Split the key.
Change file permissions.
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STORE KEY ON EXTERNAL STORAGE DEVICE Key is stored on USB or External Hard Drive
Attack must be executed locally or attacker must try every possible key to see if your database decrypts (brute force)
Requires user to provide key at start up. Unreasonable. USB is lost or damaged
My favorite solution
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DO NOT STORE THE KEY AT ALL Most interesting
Relies on password strength
When the user attempts to log in, take the user’s password, do the hash cipher hash steps, see if it decrypts the database
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HASHING Irreversible function.
Used to mainly store passwords
How to log in Hash the password given by the user Check to see if the hash given by the user equals the
hash stored in the database. Do they match?
Must be cautious when hashing Susceptible to
Look-up tables Brute-force and dictionary attacks
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TYPES OF ATTACKS Look-up table
Brute Force and Dictionary Attacks
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LOOK UP TABLES Pre-computed table for reversing hash
functions. Takes the hashes of commonly used passwords
and matches them to the hashes stored in the database
Hash matching game
Used to crack multiple passwords at a time
Work because each password is hashed the exact same way. Hash of “dog” will result in the same hash every
time. As long as you are using the same algorithm.
Hash of “dog” using md5 != hash of “dog” using SHA
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HOW TO DEFEND YOUR HASH… Look Up tables
Salt the Master Password using Cryptographically Secure Pseudo-Random Number Generator hash(“password" + “RxFLuENMsoeD") =
9c22122442a125612s62310219e025218129210 USING SHA-256
Avoids collision
This is done N amount of times
The salt and hash are stored in the database Works because it takes a lot of time to rework a
table.
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EXAMPLE
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SALTING THE CORRECT WAY do not do this
Hash( hash( hash( password+salt ) ) ) Hashing the same value does not increase security
Hash( hash( password ) + hash( salt ) ) These are argued by others
Access to source code
Use a Cryptographically Secure Pseudo Random Number Generator (CSPRNG) A Random Number Generator was not made to
be used for cryptography. Use a large enough CSPRNG
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PIGEON HOLE PRINCIPLE
• If there are more balls than boxes, then some box must contain more than one wall.
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SALT SIZE Do not want to reuse salts
Chances of collision become non-negligible at 2^n/2 salts
Byte[] salt = new Byte[8] 8 bytes * 8 bits per byte = 64 2^64 possible salts
It is better to be safer than sorry Use a 16 byte array 2^128 possible salts.
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THERE ARE OTHER METHODS TO HASH COLLISION Concatenating the salt with other variables
User name, session id, curser location, etc…
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BRUTE FORCE AND DICTIONARY ATTACKS Brute Force
Try every possible combination to a fixed length.
Dictionary Attack Can be used to crack individual passwords. List of words (dictionary) or commonly used
passwords.
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SLOWING BRUTE FORCE ATTACKS SHA-256 is designed to be fast
Can’t use wait statements
PBKDF2 Has multiple parameters
Value that will be hashed Salt Work factor
Has tons of algorithms that it can be used with SHA-256 SHA-1 AES BlowFish Etc.
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NONE OF THIS REALLY MATTERS IF Law #5: None of this matters if it’s a weak
password.• Technet.microsoft.com
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PASSWORD LENGTH Suppose there are 95 ASCII characters
Lower Case Letters = 26 Upper Case Letters = 26 Digits = 10 Special Characters = 33 TOTAL = 95
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HOW DOES HASHING WORK?
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INTRODUCTION Review the hash function SHA-256
Goal: understand how SHA-256 computes it’s hash.
Why have I decided to focus on Sha-256 algorithms? Battle tested Considered to be some of the “safest” algorithms
Bitcoin is based around SHA-256.
The way the algorithm is implemented using MessageDigest left a lot of unknowns. Was under the impression that I would need to code the
algorithm.
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MORE INTRO Named after it’s digest length.
Will not focus on SHA-1 because it has been “broken”
Would rather focus on today’s standard rather than the past.
SHA-384 and SHA-512 because they are essentially the same.
Why go over the code? I believe it is necessary to understand the code of
an algorithm in order to comprehend how hashing works.
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WHAT IS A HASH? Hash function takes a string of any length,
and generates fixed-length output data.
It is not reversible. Because a lot of data is discarded during the
hash process.
If you have lost information about the original input, then it is nearly impossible to reverse the hash.
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WHAT MAKES A GOOD HASH? Same input will always lead to the same output.
Avoids collision attacks What is a collision attack?
Find two input strings that produce the same hash. “abc” “aiieagnea;[sagjeiao;iaeohgao;ejagea”
Hash functions can have infinite input length, but a fixed output.
Sha 256 is more safe from collision attacks than other algorithms.
MD5 = 128 byte output, 64 bits of security SHA-1 = 160 byte output, 80 bits of security. SHA 256 = 256 byte output, 128 bits of security
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HOW DOES IT WORK? Padding aka Preprocessing
Block decomposition
Hash Algorithm
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PREPROCESSING Message (M) is l bits long.
Append message with a 1 Followed by n zero bits. N is smallest, non-
negative solution to the equation. L + 1 + n = 448 mod 512
This leaves enough room to append what we have so far with a 64-bit block that equals our message represented in binary. Message = “abc” 24 + 1 + N = 448 N = 423 zero bits
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NOTATION Algorithm uses AND, XOR, OR, Circular Right
Shift, and Logical Right Shifts in order to compute the hash.
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AND JAVA SYMBOL: & p q p AND q1 1 11 0 00 1 00 0 0
Produces 1 if both p and q are 1’s.
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OR JAVA SYMBOL: |
p q p OR q1 1 11 0 10 1 10 0 0
Produces 1 if p or q are 1
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XOR JAVA: ^p q p XOR q1 1 01 0 10 1 10 0 0
Produces 1 if p or q is 1, but not both.
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CIRCULAR SHIFT RIGHT SHR(VARIABLE, NUMBER) >> signed right shift
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LOGICAL RIGHT SHIFTROTR(VARIABLE, NUMBER) >>> unsigned right shift
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EQUATIONS
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WHERE IT STARTS TO GET COMPLICATED. Generally H1 – H8 are set to the first 32 bits of
the fractional parts of the square roots of the first eight primes.
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EXAMPLE Square root of 2 =
1.414213562373095048801
Fractional part = 0.41421356237309504.
Hexadecimal = 6A09E667.
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WHERE DOES OUR PASSWORD COME INTO PLAY? Or original password was padded to 512 bits.
Which is 16, 32 bit components. A 64 component array is created we will refer
to as W W0 – W15 are initialized to our padded
password. The rest (W16 – W63) are set to a value
determined by this function J is just the counter in a for loop.
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ALGORITHM COMPUTATION(EXECUTED 64 TIMES)
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A – H are initialized with H1 – H8
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LAST STEP Take your original and H1 – H8 add a – h to
them.
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DEMONSTRATION
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ISSUES WITH RESEARCH Putting together a puzzle
Some things are difficult to find answers to.
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CONCLUSION There are a lot of factors when it comes to
storing information Encrypt your database Spend some time on creating a random
secure key Salt your hashes Slow down your hashing algorithm Nothing matters if you are hashing a weak
password Sha-256 is an interesting algorithm
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QUESTIONS?
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SOURCES Algorithm
http://csrc.nist.gov/groups/STM/cavp/documents/shs/sha256-384-512.pdf
http://www-ma2.upc.es/~cripto/Q2-06-07/SHA256english.pdf
Actual Implementation http://www.cs.mcgill.ca/~
zcao7/mutls/release/llvm-gcc-4.2-2.9.source/libjava/classpath/gnu/java/security/hash/Sha256.java
http://www.vipan.com/htdocs/bitwisehelp.html
Various Information wikipedia.org/ http://www.makeuseof.com/tag/md5-hash-stuff-means-
technology-explained/
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MORE SOURCES Various Information
http://crypto.stackexchange.com/questions/8636/what-does-message-schedule-mean-in-sha-256
http://docs.oracle.com/javase/7/docs/api/java/security/MessageDigest.html
http://technet.microsoft.com/ Crackstation.net Stackexchange & stackoverflow keepass,.info/help/base/security.html Blog.agilebits.com
Converting bytes to a string http://www.mkyong.com/java/how-do-convert-byte-array-to-string-in-java/
Hash Calculator http://www.xorbin.com/tools/sha256-hash-calculator