1. The Design and Analysis of Graphical Passwords
Ian Jermyn
New York University
Alain Mayer, Fabian Monrose, Michael K.Reiter
Bell Labs, Lucent Technologies
Aviel D.Rubin
AT&T Labs-Research
Presenter :
Ta Duy Vuong

2. OUTLINE Introduction Textual Passwords with Graphical Assistance
Purely Graphical Passwords
Other graphical password scheme
Summary
References

3. 1.INTRODUCTION Passwords: method of choice for user authentication.
In practice, passwords are susceptible to attacks.
Exploit features of graphical input displays to achieve better security.

4. 1.INTRODUCTION Used for any devices with graphical input display
Primarily for PDAs: Palm Pilot, HP iPAQ,…

5. 1.INTRODUCTION Observation: temporal order & position
Textual password input via keyboard:
Graphical password
simplepass

6. 2.TEXT WITH GRAPHICAL ASSISTANCE
GRAPHICAL PASSWORD
TEXTUAL PASSWORD WITH GRAPHICAL ASSISTANCE
DRAW-A-SECRET SCHEME

7. 2.TEXT WITH GRAPHICAL ASSISTANCE
Use textual passwords augmented by some graphical capabilities.
Aim: to decouple temporal order & position of input.

8. 2.TEXT WITH GRAPHICAL ASSISTANCE
Example: password is “tomato”.
Usual way of input:
Conventional

9. 2.TEXT WITH GRAPHICAL ASSISTANCE

10. 2.TEXT WITH GRAPHICAL ASSISTANCE
Formally:
k : number of characters in password
A : set of allowed characters
m : number of positions (m>=k)
Textual : f = {1,…,k}  A
Graphical : f’ = {1,…,k}  A x {1,…,m}

11. 2.TEXT WITH GRAPHICAL ASSISTANCE
One k-character conventional password yields:
m!/(m-k)! graphical passwords
Ex: Password is “ILoveNus”
k=8 (characters)
Choose m=10 (positions)
 approximately 1.8 x 106 graphical passwords

12. 3.DRAW-A-SECRET (DAS) SCHEME
GRAPHICAL PASSWORD
TEXTUAL PASSWORD WITH GRAPHICAL ASSISTANCE
DRAW-A-SECRET SCHEME

13. 3.DRAW-A-SECRET (DAS) SCHEME 3.1 Introduction
Password is picture drawn on a grid.
Users freed from having to remember alphanumeric string.
What is good about picture-based password?

14. 3.DRAW-A-SECRET (DAS) SCHEME 3.2 Password input
(2,2) (3,2) (3,3) (2,3) (2,2) (2,1) (5,5)
(5,5) is pen-up indicator

15. 3.DRAW-A-SECRET (DAS) SCHEME 3.3 Encryption Tool for PDA
Use Triple-DES to encrypt/decrypt data stored on PDA
Key k
Triple-DES
Sequence of coordinates of password P
Hashed using SHA-1
Derived to make keys
Process of making keys for Triple-DES

16. 3.DRAW-A-SECRET (DAS) SCHEME 3.3 Encryption Tool for PDA
Store Ek(P)
Key k
Ek(P)
Sequence of coordinates P
Hashed using SHA-1
Process of setting password
ressult = P ??
Key k’
restult=Dk’(Ek(P))
Sequence of coordinates P’
Hashed using SHA-1
Process of verifying password

17. 3.DRAW-A-SECRET (DAS) SCHEME 3.4 Security of the DAS Scheme
Textual passwords are susceptible to attacks because:
Users do not choose passwords uniformly.
Attackers have significant knowledge about the
distribution of user passwords (users often choose passwords based their own name…)
information about gross properties (words in English dictionary are likely to be chosen)

18. 3.DRAW-A-SECRET (DAS) SCHEME 3.4 Security of the DAS Scheme
Knowledge about the distribution of user password is essential to adversary.
DAS scheme gives no clues about user choice of passwords.
Harder to collect data on PDAs than networked computers.

19. 3.DRAW-A-SECRET (DAS) SCHEME 3.4 Security of the DAS Scheme
Size of Password space:
Lmax P : password
∏(Lmax,G) = ∑ P(L,G) Grid size GxG
L=1 L : length of password
Lmax : maximum length of password
l=L N: number of strokes
P(L,G) = ∑ P(L-l,G)N(lG) l : length of stoke
l=1
N(l,G) = ∑ n(x,y,l,G) n : number of strokes of length l
(x,y)∈[1..G]x[1..G] (x,y) : ending cell

20. 3.DRAW-A-SECRET (DAS) SCHEME 3.4 Security of the DAS Scheme
New password scheme cannot be proven better than old scheme because of human factor !
However, above table shows raw size of graphical password space surpasses that of textual passwords.

21. 4. Another graphical password scheme
To login, user is required to click within the circled red regions (chosen when created the password) in this picture. The choice for the four regions is arbitrary
Known since the mid 1990s, starting with G.Blonder in his paper “Graphical Passwords”

22. 5. SUMMARY
Textual passwords with graphical assistance: conventional passwords equipped with graphical capabilities.
Improvements over textual passwords:
Decouple positions of input from temporal order
Larger password space

23. 5. SUMMARY Draw-A-Secret (DAS) Scheme: Pictures are easier to remember
Attackers have no knowledge of the distribution of passwords
Larger password space
Decouple position of inputs from temporal order

24. 6. REFERENCES
“The Design and Analysis of Graphical Passwords” by Ian Jermyn, Alain Mayer, Fabian Monrose, Michael K.Reiter, Aviel D.Rubin
“Graphical passwords” by Leonardo Sobrado, Jean-Camille Birget, Department of Computer Science, Rutgers University
“Graphical Dictionaries and the Memorable Space of Graphical Passwords” by Julie Thorpe, P.C. van Oorschot
“Human Memory and the Graphical Password” by David Bensinger, Ph.D.
“Passwords: the weakest link?” CNET News.com

25. THANK YOU .