i mproving y our p assword with s alt tayler angevine bachelor of arts in computer science dr. ken...

IMPROVING YOUR PASSWORD WITH SALT

Tayler Angevine

Bachelor of Arts in Computer Science

Dr. Ken Blaha (Advisor)

May 03, 2014

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

“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)

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

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

WHAT IS CRYPTOGRAPHY?

Secret writing

The computerized encoding and decoding of information Symmetric-key cryptography Hashing

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

ADVANCED ENCRYPTION STANDARD (AES)

Two-way symmetric encryption algorithm.

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.

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

KEY DERIVATION CONTINUED…

Plenty of Libraries for creating secret keys Java’s

SecretKeyFactory SecretKey

STORING THE KEY

Key must be stored in order to encrypt and decrypt data. Problem that’s been around for years

STORING KEY IN DATABASE

Common Solution

Risky

STORING KEY IN SEPARATE FILE

Common Solution

Risky Anything done in code can be undone. Humans are predictable

Split the key.

Change file permissions.

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

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

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

TYPES OF ATTACKS

Look-up table

Brute Force and Dictionary Attacks

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

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.

EXAMPLE

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

PIGEON HOLE PRINCIPLE

• If there are more balls than boxes, then some box must contain more than one wall.

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.

THERE ARE OTHER METHODS TO HASH COLLISION

Concatenating the salt with other variables User name, session id, curser location, etc…

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.

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.

NONE OF THIS REALLY MATTERS IF

Law #5: None of this matters if it’s a weak password.

• Technet.microsoft.com

PASSWORD LENGTH

Suppose there are 95 ASCII characters Lower Case Letters = 26 Upper Case Letters = 26 Digits = 10 Special Characters = 33 TOTAL = 95

HOW DOES HASHING WORK?

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.

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.

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.

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

HOW DOES IT WORK?

Padding aka Preprocessing

Block decomposition

Hash Algorithm

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

NOTATION

Algorithm uses AND, XOR, OR, Circular Right Shift, and Logical Right Shifts in order to compute the hash.

AND JAVA SYMBOL: &

p q p AND q

1 1 1

1 0 0

0 1 0

0 0 0

Produces 1 if both p and q are 1’s.

OR JAVA SYMBOL: |

p q p OR q

1 1 1

1 0 1

0 1 1

0 0 0

Produces 1 if p or q are 1

XOR JAVA: ^

p q p XOR q

1 1 0

1 0 1

0 1 1

0 0 0

Produces 1 if p or q is 1, but not both.

CIRCULAR SHIFT RIGHT SHR(VARIABLE, NUMBER)

>> signed right shift

LOGICAL RIGHT SHIFTROTR(VARIABLE, NUMBER)

>>> unsigned right shift

EQUATIONS

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.

EXAMPLE

Square root of 2 = 1.414213562373095048801

Fractional part = 0.41421356237309504.

Hexadecimal = 6A09E667.

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.

ALGORITHM COMPUTATION(EXECUTED 64 TIMES)

A – H are initialized with H1 – H8

LAST STEP

Take your original and H1 – H8 add a – h to them.

DEMONSTRATION

ISSUES WITH RESEARCH

Putting together a puzzle Some things are difficult to find answers to.

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

QUESTIONS?

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/

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