PasswordsChanging times

Two ways forward

The Changing Landscape of Passwords

Ryan Smith, Ph.D.Data Scientist

August 18, 2014

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

Definition

A hash function is a ’one way’ function that scrambles the input sothat a) it’s infeasible to guess the input from the output, and b)slight changes to the input have a large effect on the output.

Input Hashed Output

password 5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8Password 8be3c943b1609fffbfc51aad666d0a04adf83c9d1234 7110eda4d09e062aa5e4a390b0a572ac0d2c0220DB+U44@5wK83g*6 df3c73999cc44aabbba6c7167cc8a846a7425f43

Table: Hashes using the SHA-1 algorithm

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

Definition

A hash function is a ’one way’ function that scrambles the input sothat a) it’s infeasible to guess the input from the output, and b)slight changes to the input have a large effect on the output.

Input Hashed Output

password 5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8Password 8be3c943b1609fffbfc51aad666d0a04adf83c9d1234 7110eda4d09e062aa5e4a390b0a572ac0d2c0220DB+U44@5wK83g*6 df3c73999cc44aabbba6c7167cc8a846a7425f43

Table: Hashes using the SHA-1 algorithm

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

How do hash functions affect your life?

Data integrity

Bitcoin

All password-based authentication

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

How do hash functions affect your life?

Data integrity

Bitcoin

All password-based authentication

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

How do hash functions affect your life?

Data integrity

Bitcoin

All password-based authentication

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

How password authentication works

1 User enters their password

2 Server computes the hash of their password3 Server compares the hashed password to a master list

[root@localhost ~]# cat /etc/shadow

root:$1$flVALfyK$ kJfaoYnsAm7/plT3.PCmJ/ :15816:0:99999:7:::

bob:$1$MIyV9col$ Up9YON8Z.TI1x37xgFvuO0 :15804:0:99999:7:::

sue:$1$0Iwvz7CA$ QOJLfOSJZuSLC19LSFxt1. :15810:0:99999:7

4 User is authenticated or denied.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

How password authentication works

1 User enters their password

2 Server computes the hash of their password3 Server compares the hashed password to a master list

[root@localhost ~]# cat /etc/shadow

root:$1$flVALfyK$ kJfaoYnsAm7/plT3.PCmJ/ :15816:0:99999:7:::

bob:$1$MIyV9col$ Up9YON8Z.TI1x37xgFvuO0 :15804:0:99999:7:::

sue:$1$0Iwvz7CA$ QOJLfOSJZuSLC19LSFxt1. :15810:0:99999:7

4 User is authenticated or denied.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

How password authentication works

1 User enters their password

2 Server computes the hash of their password3 Server compares the hashed password to a master list

[root@localhost ~]# cat /etc/shadow

root:$1$flVALfyK$ kJfaoYnsAm7/plT3.PCmJ/ :15816:0:99999:7:::

bob:$1$MIyV9col$ Up9YON8Z.TI1x37xgFvuO0 :15804:0:99999:7:::

sue:$1$0Iwvz7CA$ QOJLfOSJZuSLC19LSFxt1. :15810:0:99999:7

4 User is authenticated or denied.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

How password authentication works

1 User enters their password

2 Server computes the hash of their password3 Server compares the hashed password to a master list

[root@localhost ~]# cat /etc/shadow

root:$1$flVALfyK$ kJfaoYnsAm7/plT3.PCmJ/ :15816:0:99999:7:::

bob:$1$MIyV9col$ Up9YON8Z.TI1x37xgFvuO0 :15804:0:99999:7:::

sue:$1$0Iwvz7CA$ QOJLfOSJZuSLC19LSFxt1. :15810:0:99999:7

4 User is authenticated or denied.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

”... because that’s where the money is”

How do attackers compromise password lists?

SQL injection attacks

Cross-site scripting

Buffer overflows

. . .

Avoid single points of failure

Password policies should assume that an attacker has access to thelist of hashed master passwords.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

”... because that’s where the money is”

How do attackers compromise password lists?

SQL injection attacks

Cross-site scripting

Buffer overflows

. . .

Avoid single points of failure

Password policies should assume that an attacker has access to thelist of hashed master passwords.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

Guess and check

Example

Suppose the hash of Laura’s password is d83f445224a58355b13.

Password Hash

cat 3389fc855f142c3d40ffluffy e1e986bc62f6c988ddwhiskers 8ae5f0c19282e29f203. . . . . .kitten42 d83f445224a58355b13

We know that Laura’s password was kitten42

Danger

These are not hypothetical attacks! John the Ripper and Hashcatare both widely available.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Hash FunctionsDefeating password authentication

Guess and check

Example

Suppose the hash of Laura’s password is d83f445224a58355b13.

Password Hash

cat 3389fc855f142c3d40ffluffy e1e986bc62f6c988ddwhiskers 8ae5f0c19282e29f203. . . . . .kitten42 d83f445224a58355b13

We know that Laura’s password was kitten42

Danger

These are not hypothetical attacks! John the Ripper and Hashcatare both widely available.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Enter the GPUThe Cloud

Order of magnitude comparisons

Definition

Embarrassingly parallel problems scale perfectly with moreprocessor power

Device Cores NTLM hashes per second

Intel Core i5 4 5-15 million attempts per secondNVIDIA GTX 690 3072 12-14 billion of attempts per second

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Enter the GPUThe Cloud

Order of magnitude comparisons

Definition

Embarrassingly parallel problems scale perfectly with moreprocessor power

Device Cores NTLM hashes per second

Intel Core i5 4 5-15 million attempts per secondNVIDIA GTX 690 3072 12-14 billion of attempts per second

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Enter the GPUThe Cloud

GPU computing

A cluster of 25 AMD RadeonHD6990s achieved:

350 billion guesses persecond using NTLMhashing,

a complete search of alleight character passwordswith uppercase, lower case,letters, digits, and symbolsin six hours!

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Enter the GPUThe Cloud

Remark

Why run one GPU for 100 hours, when you could run 100 GPU’sfor one hour?

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Repeated hash functionsThird party authentication

Repeated hash functions

Apply a hash function more than once

SHA1(SHA1(“doge”)) = SHA1(aa3cca7d . . .)

= 59c77262 . . .

This is not always such a bad idea, encrypted .dmg files on OS Xuse 250,000 iterations of SHA1.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Repeated hash functionsThird party authentication

Repeated hash functions

Apply a hash function more than once

SHA1(SHA1(“doge”)) = SHA1(aa3cca7d . . .)

= 59c77262 . . .

This is not always such a bad idea, encrypted .dmg files on OS Xuse 250,000 iterations of SHA1.

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords

PasswordsChanging times

Two ways forward

Repeated hash functionsThird party authentication

Let someone else solve the problem for you

Build your websites to use a third party authentication

OpenID - Google, Yahoo, Twitter

Facebook Connect

OAuth 2.0

Ryan Smith, Ph.D. Data Scientist The Changing Landscape of Passwords