SECURITY and CRYPTOGRAPHY 15-827                  2 OCT 01
            Lecture #5                                   M.B.
                                                      4615 Wean

READINGS (suggested by Doug TYGAR):

The deja vu project pages are at:

http://www.sims.berkeley.edu/~rachna/dejavu/
http://paris.cs.berkeley.edu/%7Eperrig/projects.html#DEJAVU

"Hash Visualization: a way to improve real world security"
Adrian Perrig and Dawn Song
http://paris.cs.berkeley.edu/%7Eperrig/projects/validation/ validation.ps
http://paris.cs.berkeley.edu/%7Eperrig/projects/validation/ validation.pdf

"Deja Vu: A User Study Using Images for Authentication"
Rachna Dhamija and Adrian Perrig
http://paris.cs.berkeley.edu/%7Eperrig/projects/usenix2000/ usenix.ps
http://paris.cs.berkeley.edu/%7Eperrig/projects/usenix2000/ usenix.pdf

"Timing Analysis of Keystrokes and SSH Timing Attacks"
Dawn Song, David Wagner, and Xuqing Tian
http://paris.cs.berkeley.edu/~dawnsong/papers/ssh-timing.ps
http://paris.cs.berkeley.edu/~dawnsong/papers/ssh-timing.pdf



PHONOIDS = challenge-response protocols for use over the phone.

In class, show off protocols # 
7,   broken by Alex TANG
30, broken by ke YANG
31(Rudich), broken by Luis von AHN
34, broken by VENKatesh
44.
Have the class break them. 
* Determine the number of challenge-response pairs the class needs to break
each one.
* After breaking a protocol, ask students how they would go about improving
it. 


HW: Break Phonoid Protocol #67 by reducing the possible responses to a
random challenge from 1/1000 to 1/100, or better, to 1/10.

Protocol #67 takes as input a challenge string abc of 3 distinct
characters, and outputs a response string uvw of 3 digits. To get uvw from
abc, it first maps characters abc to digits ABC using a randomly chosen
private fixed mapping f from characters to digits. It then performs a
randomly chosen but fixed linear mapping mod 10 to get 3 digits UVW. It
then performs a randomly chosen private fixed 1:1 mapping g from digits to
digits to get uvw.

Here are some typical challenge-response pairs for #67: 
abc = the red fox bit the  nasty dog who ate his ear off
uvw = 423 312 354 057 423  902   395 215 507 501 570 434