Trustworthy Computing in My Mind: A Case Study on Visual Password

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Trustworthy Computing in My Mind A Case Study on
Visual Password
Shujun LiVisiting Student at VC Group, Microsoft
Research Asia Institute of Image
ProcessingXian Jiaotong UniversityApril, 2002
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Table of Contents

• What is Trustworthy Computing?
• Does Perfect Trustworthiness Exist?
• How to Increase Trustworthiness?
• A Case Study Visual Password
• What/Why/How about Visual Password
• Some Proposed Schemes
• A Comparison Between Visual Password and Textual
  Password from Trustworthy Viewpoint
• Problems, Principles and Solutions

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1. What is Trustworthy Computing?

• Trustworthy computing is a label for a whole
  range of advances that have to be made for people
  to be as comfortable using devices powered by
  computers and softwares as they are today using a
  device that is powered by electricity.
  Microsoft White Paper Trustworthy Computing
• Trustworthy computing is a multi-dimensional set
  of issues good availability for almost needs
  requested by the users, acceptable reliability of
  provided services, high security of users data
  and system configurations, recoverability of
  damaged systems and lost data, full control of
  users data only by themselves with suitable
  manners, great reputation of the services
  providers, etc.

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2. Does Perfect Trustworthiness Exist?

• Nothing is perfect. We can only provide ENOUGH
  trustworthiness in practice.
• It is very hard to give a right definition of
  trustworthiness. Trustworthiness is a complicated
  concept in both technical and social world.
• An architecture built on diversity is robust,
  but it also operates on the edge of chaos. As a
  natural result, it is very difficult to exactly
  analyze the trustworthiness of
• Trade-offs exist between the different
  requirements of perfect trustworthiness. For
  example, higher security always corresponds to
  less usability, higher trustworthiness needs more
  costs in many cases.

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3. How to Increase Trustworthiness?

• Avoid using insecure codes
• Trustworthiness first, not new features
• Adopt suitable algorithms to protect the security
  and integrity of users data and systems
• Keep in mind that a computing system is only as
  trustworthy as its weakest link
• Users-centered design, coding and support
• Keep things simple to enhance usability and
  long-term and large-scale reliability
• More redundancy trend to less risks

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4a. A Case Study Visual Password

• What is Visual Password?
• The user interface by which one can generate
  password with graphical/visual operations, such
  as movement and clicking of mouse on a picture.
• Why Use Visual Password?
• It may provide higher trustworthiness than
  traditional textual password.
• How to Make Visual Password?
• Some schemes have been proposed, we will briefly
  introduce and analyze those ideas. Some
  principles and more potential solutions will also
  be discussed.

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4b. Some Proposed Schemes

• Drawing-Based Visual Password I. Jermyns
  Graphical Password for PDA
• Visual Password Based on Selected Secret Pictures
  from a Picture Database PassFaceTM and Déjà Vu
  System
• Click-by-Click Visual Password Blonders Patent,
  PassPicTM, Passlogix v-GOTM Graphical Password
  Window, Darko Kirovskis System (Microsoft)
• More details about proposed schemes are
  needed for further investigations.

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4c. A Comparison Between Visual Password and
Textual Password
Textual Password Visual Password
Usability Inconvenient for young children and the blind Inconvenient for the blind
Memorizablity Security to Dictionary Attack Easily-memorizable passwords are weak to dictionary attack, while good ones are generally hard to be memorized. Many strong passwords may be easily memorized. Dictionary attack becomes more hard.
Security to Shoulder-Surfing Attack The slower the typewriting speed, the weaker the security. All proposed schemes cannot resist shoulder-surfing attack.
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4d. Problems How to Resist Shoulder-Surfing
Attack?

• How does shoulder-surfing attack work?
• Once one impostor peeps legal users login
  actions, he can repeat those actions to cheat the
  login system, without guessing the right password
  behind such login actions.
• How to resist shoulder-surfing attack?
• The login operations of different logins must not
  be same. We call such a feature time-variant
  login-actions.
• How to obtain time-variant property?
• Pseudo-randomization mechanism may be helpful.

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4d. Principles Visual Password

1. Larger strong key space than textual password
2. Similar or better usability than textual
   password a) easy user interface b) good
   memorizability.
3. Resistance to shoulder-surfing attack Is such a
   capability possible? (Clue a shoulder-surfing
   attacker can see what you can see and understand
   what you can understand people hate hard
   deduction required by time-variant
   login-actions.)
4. Acceptable solution of the trade-off between
   usability and security.

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4d. Solutions A Theoretical Model of Visual
Password Login System Resisting Shoulder-Surfing
Attack
Here, PCNL should satisfy the following
requirements deducing the actions in the next
login is easy enough for legal users who know the
password, but is hard enough for illegal users
who have monitored your previous logins.
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4d. Problems Is a Practical PCNL Possible?

• In fact, a PCNL is a trapdoor function from
  cryptographic viewpoint.
• Human beings are not machines and hate
  complicated deduction, a PCNL MUST be easy enough
  for any users, including young children.
• Legal users may forget what they input in the
  last login, clues should be given to remind them.
  Consider such clues may be also peeped by an
  impostor, they should not provide useful
  information to him under the assumption that he
  does not know password.
• Now I have not found a really practical
  PCNL. Does a practical PCNL exist? We try to find
  the answer.

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4d. Solutions More Fresh Ways?

1. More Click-by-Click Visual Passwords Visual
   Password Based on Clicking Picture Properties,
   such as differences of a pair of pictures, the
   relations between two countries in a world map,
   the geometry properties of elements in a computer
   painting.
2. Visual Passwords Based on Specially-Designed
   Input Devices a) Device tracking users eyes b)
   Strange mouse that can generate password by
   ones touching different parts c) Strange
   glasses that can generate different scenes from
   different view directions with enough sensitivity.

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Thanks For your watching and advice!