A Seminar Report on
3D PASSWORD
Submitted to the Dept. of Information Technology, SNIST In the
partial fulfilment of the academic requirements for the award ofB.
Tech (IT) under JNTU
by
Ms.S.Pranitha (11311A1254)
Department of Information TechnologySchool of Computer Science
and Informatics
Sree Nidhi Institute of Science and TechnologyYamnampet,
Ghatkesar Mandal, R.R Dist., Hyderabad 501 301
CERTIFICATE
This is to certify that the seminar report on 3D Password is a
bonafide work carried out by S.Pranitha (11311A1254), respectively
in the partial fulfilment for the award of B.Tech degree in
Information Technology, Sree Nidhi Institute of Science and
Technology, Hyderabad, affiliated to Jawaharlal Nehru Technological
University, Hyderabad under our guidance and supervision.
The results embodied in the project work have not been submitted
to any other University or Institute for the award of any degree or
diploma.
Head of the Department Prof. V. Balaram
CONTENTS
1. INTRODUCTION32. WHAT IS AUTHENTICATION43. AUTHENTICATION
METHODS 44. BRIEF DESCRIPTION OF THE SYSTEM5
5. INNOVATIVE COMPONENT6
6. WHAT IS 3D PASSWORD7
7. STATE DIAGRAM8
8. SYSTEM IMPLEMENTATION9
9. DESIGN OF 3D VIRTUAL ENVIRONMENTS14
10. APPLICATION15
11. SECURITY ANALYSIS17
12. ATTACKS18
13. CONCLUSION 22
14. FUTURE WORKS 23
15. REFERENCES24
INTRODUCTION
Users nowadays are provided with major password stereotypes such
as textual passwords, biometric scanning, tokens or cards (such as
an ATM) etc. Current authentication systems suffer from many
weaknesses. Textual passwords are commonly used; however, users do
not follow their requirements. Users tend to choose meaningful
words from dictionary or their pet names, girlfriends etc. Ten
years back Klein performed such tests and he could crack 10-15
passwords per day. On the other hand, if a password is hard to
guess, then it is often hard to remember. Users have difficulty
remembering a password that is long and random appearing. So, they
create short, simple, and insecure passwords that are susceptible
to attack. Which make textual passwords easy to break and
vulnerable to dictionary or brute force attacks. Graphical
passwords schemes have been proposed. The strength of graphical
passwords comes from the fact that users can recall and recognize
pictures more than words. Most graphical passwords are vulnerable
for shoulder surfing attacks, where an attacker can observe or
record the legitimate users graphical password by camera. Token
based systems such as ATMs are widely applied in banking systems
and in laboratories entrances as a mean of authentication. However,
Smart cards or tokens are vulnerable to loss or theft. Moreover,
the user has to carry the token whenever access required. Biometric
scanning is your "natural" signature and Cards or Tokens prove your
validity. But some people hate the fact to carry around their
cards, some refuse to undergo strong IR exposure to their retinas
(Biometric scanning). In this paper, we present and evaluate our
contribution, i.e., the 3-D password. The 3-D password is a
multifactor authentication scheme. To be authenticated, we present
a 3-D virtual environment where the user navigates and interacts
with various objects. The sequence of actions and interactions
toward the objects inside the 3-D environment constructs the users
3-D password. The 3-D password can combine most existing
authentication schemes such as textual passwords, graphical
passwords, and various types of biometrics into a 3-D virtual
environment. The design of the 3-D virtual environment and the type
of objects selected determine the 3-Dpassword key space.
WHAT IS AUTHENTICATION? Authentication is the act of
establishing or confirming something as authentic, that is, that
claims made by or about the subject are true. This might involve
confirming the identity of a person, tracing the origins of an
artifact, ensuring that a product is what its packaging and
labeling claims to be, or assuring that a computer program is a
trusted one. For example, when you show proper identification
credentials to a bank teller, you are asking to be authenticated to
act on behalf of the account holder. If your authentication request
is approved, you become authorized to access the accounts of that
account holder, but no others.
AUTHENTICATION METHODS
There are two types of techniques for doing this. The first is
comparing the attributes of the object itself to what is known
about objects of that origin. For example, an art expert might look
for similarities in the style of painting, check the location and
form of a signature, or compare the object to an old photograph. An
archaeologist might use carbon dating to verify the age of an
artifact, do a chemical analysis of the materials used, or compare
the style of construction or decoration to other artifacts of
similar origin. The physics of sound and light, and comparison with
a known physical environment, can be used to examine the
authenticity of audio recordings, photographs, or videos. The
second type relies on documentation or other external affirmations.
For example, the rules of evidence in criminal courts often require
establishing the chain of custody of evidence presented. This can
be accomplished through a written evidence log, or by testimony
from the police detectives and forensics staff that handled it.
Some antiques are accompanied by certificates attesting to their
authenticity. External records have their own problems of forgery
and perjury, and are also vulnerable to being separated from the
artifact and lost.
Currency and other financial instruments commonly use the first
type of authentication method. Bills, coins, and cheques
incorporate hard-to-duplicate physical features, such as fine
printing or engraving, distinctive feel, watermarks, and
holographic imagery, which are easy for receivers to verify.
Consumer goods such as pharmaceuticals, perfume, fashion clothing
can use either type of authentication method to prevent counterfeit
goods from taking advantage of a popular brand's reputation
(damaging the brand owner's sales and reputation). A trademark is a
legally protected marking or other identifying feature which aids
consumers in the identification of genuine brand-name goods.
BRIEF DESCRIPTION OF THE SYSTEM
The proposed system is a multi factor authentication scheme. It
can combine all existing authentication schemes into a single
3Dvirtual environment. This 3D virtual environment contains several
objects or items with which the user can interact. The user is
presented with this 3D virtual environment where the user navigates
and interacts with various objects. The sequence of actions and
interactions toward the objects inside the 3D environment
constructs the users 3Dpassword.The 3D password can combine most
existing authentication schemes such as textual passwords,
graphical passwords, and various types of biometrics into a 3D
virtual environment. The choice of what authentication schemes will
be part of the user's 3D password reflects the user's preferences
and requirements. A user who prefers to remember and recall a
password might choose textual and graphical password as part of
their 3D password. On the other hand users who have more difficulty
with memory or recall might prefer to choose smart cards or
biometrics as part of their 3D password. Moreover user who prefers
to keep any kind of biometric data private might not interact with
object that requires biometric information. Therefore it is the
user's choice and decision to construct the desired and preferred
3D password.
INNOVATIVE COMPONENT
The proposed system is a multi factor authentication scheme that
combines the benefits of various authentication schemes. Users have
the freedom to select whether the 3D password will be solely
recall, recognition, or token based, or combination of two schemes
or more. This freedom of selection is necessary because users are
different and they have different requirements. Therefore, to
ensure high user acceptability, the users freedom of selection is
important. The following requirements are satisfied in the proposed
scheme 1. The new scheme provide secrets that are easy to remember
and very difficult for intruders to guess.
2. The new scheme provides secrets that are not easy to write
down on paper. Moreover, the scheme secrets should be difficult to
share with others.
3. The new scheme provides secrets that can be easily revoked or
changed.
COMPARISON WITH CURRENT AUTHENTICATION SYSTEMS
Suffer from many weaknesses. Textual passwords are commonly
used. Users tend to choose meaningful words from dictionaries,
which make textual passwords easy to break and vulnerable to
dictionary or brute force attacks. Many available graphical
passwords have a password space that is less than or equal to the
textual password space. Smart cards or tokens can be stolen. Many
biometric authentications have been proposed. However, users tend
to resist using biometrics because of their intrusiveness and the
effect on their privacy. Moreover, biometrics cannot be revoked.
The 3D password is a multi factor authentication scheme. The design
of the 3D virtual environment and the type of objects selected
determine the 3D password key space. User have freedom to select
whether the 3D password will be solely recall, recognition, or
token based, or combination of two schemes or more.
WHAT IS A 3D PASSWORD?
The 3-D password is a multifactor authentication scheme. It can
combine all existing authentication schemes into a single 3-D
virtual environment. This 3-D virtual environment contains several
objects or items with which the user can interact. The type of
interaction varies from one item to another. The 3-D password is
constructed by observing the actions and interactions of the user
and by observing the sequences of such actions. It is the users
choice to select which type of authentication techniques will be
part of their 3-D password. This is achieved through interacting
only with the objects that acquire information that the user is
comfortable in providing and ignoring the objects that request
information that the user prefers not to provide. For example, if
an item requests an iris scan and the user is not comfortable in
providing such information, the user simply avoids interacting with
that item. Moreover, giving the user the freedom of choice as to
what type of authentication schemes will be part of their 3-D
password and given the large number of objects and items in the
environment, the number of possible 3-D passwords will increase.
Thus, it becomes much more difficult for the attacker to guess the
users 3-D password. STATEDIAGRAMOFA3DPASSWORDAPPLICATION
SYSTEM IMPLEMENTATION IN BRIEF
The 3Dpassword is a multi factor authentication scheme. The
3Dpassword presents a 3Dvirtual environment containing various
virtual objects. The user navigates through this environment and
interacts with the objects. The 3Dpassword is simply the
combination and the sequence of user interactions that occur in the
3Dvirtual environment. The 3Dpassword can combine recognition,
recall, token, and biometrics based systems into one authentication
scheme. This can be done by designing a 3Dvirtual environment that
contains objects that request information to be recalled,
information to be recognized, tokens to be presented, and biometric
data to be verified.
For example, the user can enter the virtual environment and type
something on a computer that exists in (x1 , y1 , z1 ) position,
then enter a room that has a fingerprint recognition device that
exists in a position (x2 , y2 , z2 ) and provide his/her
fingerprint. Then, the user can go to the virtual garage, open the
car door, and turn on the radio to a specific channel. The
combination and the sequence of the previous actions toward the
specific objects construct the users 3Dpassword.
Virtual objects can be any object that we encounter in real
life. Any obvious actions and interactions toward the real life
objects can be done in the virtual3Denvironment toward the virtual
objects. Moreover, any user input (such as speaking in a specific
location) in the virtual 3Denvironment can be considered as a part
of the 3Dpassword.
We can have the following objects:1) A computer with which the
user can type;2) A fingerprint reader that requires the users
fingerprint;3) A biometric recognition device;4) A paper or a white
board that a user can write, sign, or draw on;5) An automated
teller machine (ATM) that requests a token;6) A light that can be
switched on/off;7) A television or radio where channels can be
selected;8) A staple that can be punched;9) A car that can be
driven;10) A book that can be moved from one place to another;11)
Any graphical password scheme;12) Any real life object;13) Any
upcoming authentication scheme.
The action toward an object (assume a fingerprint recognition
device)that exists in location (x1 , y1 , z1 ) is different from
the actions toward a similar object (another fingerprint
recognition device) that exists in location (x2 , y2 , z2 ),where
x1 = x2 , y1 = y2 , and z1 = z2 . Therefore, to perform the
legitimate 3Dpassword, the user must follow the same scenario
performed by the legitimate user. This means interacting with the
same objects that reside at the exact locations and perform the
exact actions in the proper sequence.
3DPASSWORD SELECTION AND INPUTS Let us consider a 3Dvirtual
environment space of size G G G. The 3Denvironment space is
represented by the coordinates (x, y, z) [1. . . G] [1. . . G] [1.
. . G]. the objects are distributed in the 3Dvirtual environment
with unique (x, y, z) coordinates. We assume that the user can
navigate into the 3Dvirtual environment and interact with the
objects using any input device such as a mouse, key board,
fingerprint scanner, iris scanner, stylus, card reader, and
microphone. We consider the sequence of those actions and
interactions using the previous input devices as the users
3Dpassword. For example, consider a user who navigates through the
3Dvirtualenvironment that consists of an office and a meeting room.
Let us assume that the user is in the virtual office and the user
turns around to the door located in (10, 24, 91) and opens it.
Then, the user closes the door. The user then finds a computer to
the left, which exists in the position (4, 34, 18), and the user
types FALCON. Then, the user walks to the meeting room and picks up
a pen located at (10, 24, 80) and draws only one dot in a paper
located in (1, 18, 30), which is the dot (x, y) coordinate relative
to the paper space is (330, 130). The user then presses the login
button.The initial representation of user actions in the 3Dvirtual
environment can be recorded as follows: (10, 24, 91) Action = Open
the office door; (10, 24, 91) Action = Close the office door; (4,
34, 18) Action = Typing, F; (4, 34, 18) Action = Typing, A; (4, 34,
18) Action = Typing, L; (4, 34, 18) Action = Typing, C; (4, 34, 18)
Action = Typing, O; (4, 34, 18) Action = Typing, N; (10, 24, 80)
Action = Pick up the pen; (1, 18, 80) Action = Drawing, point =
(330, 130).In order for a legitimate user to be authenticated, the
user has to follow the same sequence and type of actions and
interactions toward the objects for the users original 3-D
password.
Snapshot of a proof-of-concept 3-D virtual environment, where
the user is typing a textual password on a virtual computer as a
part of the users 3-D password
Snapshot of an experimental 3-D virtual environment
3D VIRTUAL ENVIRONMENT DESIGN GUIDELINES The design of the 3 D
virtual environments affects the usability, effectiveness,
acceptability of 3D password. The first step in building a
3Dpassword system is to design a 3Denvironment that reflects the
administration needs and the security requirements.
The design of 3D virtual environments should follow these
guidelines.
1) Real life-similarity The prospective 3D virtual environment
should reflect what people are used to seeing in real life. Objects
used in virtual environments should be relatively similar in size
to real objects (sized to scale). Possible actions and interactions
toward virtual objects should reflect real life situations. Object
responses should be realistic. The target should have a 3D virtual
environment that users can interact. 2) Object uniqueness and
distinction Every virtual object or item in the 3D virtual
environment is different from any other virtual object. The
uniqueness comes from the fact that every virtual object has its
own attributes such as position. Thus, the prospective interaction
with object 1 is not equal to the interaction with object 2.
However, having similar objects such as 20 computers in one place
might confuse the user. Therefore, the design of the 3D virtual
environment should consider that every object should be
distinguishable from other objects. Similarly, in designing a
3Dvirtual environment, it should be easy for users to navigate
through and to distinguish between objects. The distinguishing
factor increases the users recognition of objects. Therefore, it
improves the system usability.
3) Three Dimensional Virtual Environment Size A 3Dvirtual
environment can depict a city or even the world. On the other hand,
it can depict a space as focused as a single room or office. A
large 3D virtual environment will increase the time required by the
user to perform a 3Dpassword. Moreover, a large3Dvirtual
environment can contain a large number of virtual objects.
Therefore, the probable 3Dpassword space broadens. However, a small
3D virtual environment usually contains only a few objects, and
thus, performing a 3D password will take less time.
4) Number of objects and their types Part of designing a 3D
virtual environment is determining the types of objects and how
many objects should be placed in the environment. The types of
objects reflect what kind of responses the object will have. For
simplicity, we can consider requesting a textual password or a
fingerprint as an object response type. Selecting the right object
response types and the number of objects affects the probable
password space of a 3D password.
5) System Importance The 3D virtual environment should consider
what systems will be protected by a 3D password. The number of
objects and the types of objects that have been used in the 3D
virtual environment should reflect the importance of the protected
system.
3D PASSWORD APPLICATIONS
The 3D password can have a password space that is very large
compared to other authentication schemes, so the 3D passwords main
application domains are protecting critical systems and
resources.
1. Critical servers Many large organizations have critical
servers that are usually protected by a textual password. A 3D
password authentication proposes a sound replacement for a textual
password.
2. Nuclear and military facilities- Such facilities should be
protected by the most powerful authentication systems. The 3D
password has a very large probable password space, and since it can
contain token, biometrics, recognition, and knowledge based
authentications in a single authentication system, it is a sound
choice for high level security locations.
3. Airplanes and jet fighters Because of the possible threat of
misusing airplanes and jet fighters for religiopolitical agendas,
usage of such airplanes should be protected by a powerful
authentication system. In addition, 3D passwords can be used in
less critical systems because the 3D virtual environment can be
designed to fit to any system needs. A small virtual environment
can be used in the following systems like
Some other application areas:
ATM Desktop Computers & laptop logins Web Authentication
SECURITY ANALYSIS
To analyze and study how secure a system is, we have to
consider, How hard it is for the attacker to break such a system A
Possible measurement is based on the information content of a
password space. The textual password space may be relatively large;
however, an attacker might only need a small subset of the full
password space is observed to successfully break such an
authentication system. It is important to have a scheme that has a
very large possible password space which increases the work
required by the attacker to break the authentication system. Find a
scheme that has no previous or existing knowledge of the most
probable user password selection.
Common guidelines for choosing good passwords are designed to
make passwords less easily discovered by intelligent guessing:
Include numbers, symbols, upper and lowercase letters in
passwords if allowed by the system
Password length should be around 12 to 14 characters if
permitted, and longer still if possible while remaining
memorable
If the system recognizes case as significant, use capital and
lower-case letters
Avoid any password based on repetition, dictionary words, letter
or number sequences, usernames, relative or pet names, romantic
links (current or past), or biographical information (e.g., dates,
ID numbers, ancestors names or dates, ...). Password should be easy
to remember for the user, and not force insecure actions (e.g., the
very bad and insecure practice of writing the password down on a
Post-It note stuck to the monitor)
3D PASSWORD SPACE SIZE
To determine the password space, we have to count all possible
3D passwords that have a certain number of actions, interactions,
and inputs towards all objects that exist in the 3D virtual
environments.
FIG: Password space of the 3-D password, textual password, Pass
faces, and DAS with grid sizes of 5 5 and 10 10. Length is the
number of actions and interactions for a 3-D password, the number
of characters for textual passwords, the number of selections for
Pass faces, and the number of points that represent the strokes for
DAS. The length is up to eight.
Fig: Observing the number of possible actions/interactions of a
3-D password within a 3-D environment specified in Section V-A
compared to the two critical Points of textual passwords. Point a
is the bit size of Klein [2] (3 106) dictionary of eight-character
textual passwords. Point b represents the full password space of
eight-character textual passwords.
3D PASSWORD DISTRIBUTION KNOWLEDGE Users tend to use meaningful
words for textual passwords. Therefore finding these different
words from dictionary is a relatively simple task which yields a
high success rate for breaking textual passwords. Pass faces users
tend to choose faces that reflect their own taste on facial
attractiveness, race, and gender. Every user has different
requirements and preferences when selecting the appropriate 3D
password. This fact will increase the effort required to find a
pattern of users highly selected 3D password. In addition, since
the 3D password combines several authentication schemes into a
single authentication environment, the attacker has to study every
single authentication scheme and has to discover what the most
probable selected secrets are. Since every 3D password system can
be designed according to the protected system requirements, the
attacker has to separately study every 3D password system.
Therefore, more effort is required to build the knowledge of most
probable 3D passwords.
ADVANTAGES Easiness to memorize: Users can memorize a 3D
password as a little story which makes the password easy to
remember
Flexibility: 3d passwords allows multi-factor authentication.
Smart cards, biometrics and alpha num password can embedded in the
3d password technology
Strength: A scenario in a 3D environment offers as almost
unlimited combination of possibilities. As such system can have
specific 3d world, hack are extremely difficult.
The 3D password gives users the freedom of selecting what type
of authentication techniques.
Secrets those are not easy to write down on paper.
The scheme secrets should be difficult to share with others.
Provide secrets that can be easily revoked or changed.
ATTACKS AND COUNTERMEASURES
1) Brute Force Attack The attacker has to try all possible 3D
passwords. This kind of attack is very difficult for the following
reasons.
Time required to login The total time needed for a legitimate
user to login may vary depending on the number of interactions and
actions, the size of the 3D virtual environment, and the type of
actions and interactions. Therefore, a brute force attack on a 3D
password is very difficult and time consuming.
Cost of attacks The 3D virtual environment contains biometric
recognition objects and token based objects. The attacker has to
forge all possible biometric information and forge all the required
tokens. The cost of forging such information is very high,
therefore cracking the 3D password is more challenging. The high
number of possible 3D password spaces leaves the attacker with
almost no chance of breaking the 3D password.
2) Well Studied Attack The attacker tries to find the highest
probable distribution of 3D passwords. In order to launch such an
attack, the attacker has to acquire knowledge of the most probable
3D password distributions. This is very difficult because the
attacker has to study all the existing authentication schemes that
are used in the 3D environment. It requires a study of the users
selection of objects for the 3D password. Moreover, a well studied
attack is very hard to accomplish since the attacker has to perform
a customized attack for every different 3D virtual environment
design. This environment has a number of objects and types of
object responses that differ from any other 3D virtual environment.
Therefore, a carefully customized study is required to initialize
an effective attack
3) Shoulder Surfing Attack An attacker uses a camera to record
the users 3D password or tries to watch the legitimate user while
the 3D password is being performed. This attack is the most
successful type of attack against 3D passwords and some other
graphical passwords. However, the users 3D password may contain
biometric data or textual passwords that cannot be seen from
behind. Therefore, we assume that the 3D password should be
performed in a secure place where a shoulder surfing attack cannot
be performed.
4) Timing Attack In this attack, the attacker observes how long
it takes the legitimate user to perform a correct sign-in using the
3D password. This observation gives the attacker an indication of
the legitimate users 3D password length. However, this kind of
attack alone cannot be very successful since it gives the attacker
mere hints. Therefore, it would probably be launched as part of a
well studied or brute force attack. Timing attacks can be very
effective if the 3D virtual environment is poorly designed.
CONCLUSION
There are many authentication schemes in the current state. Some
of them are based on users physical and behavioral properties, and
some other authentication schemes are based on users knowledge such
as textual and graphical passwords. Moreover, there are some other
important authentication schemes that are based on what you have,
such as smart cards. Among the various authentication schemes,
textual password and token-based schemes, or the combination of
both, are commonly applied. However, as mentioned before, both
authentication schemes are vulnerable to certain attacks. Moreover,
there are many authentication schemes that are currently under
study and they may require additional time and effort to be
applicable for commercial use. The 3-D password is a multifactor
authentication scheme that combines these various authentication
schemes into a single3-D virtual environment. The virtual
environment can contain any existing authentication scheme or even
any upcoming authentication schemes by adding it as a response to
actions performed on an object. Therefore, the resulted password
space becomes very large compared to any existing authentication
schemes. The design of the 3-D virtual environment, the selections
of objects inside the environment, and the objects type reflect the
resulted password space. It is the task of the system administrator
to design the environment and to select the appropriate object that
reflects the protected system requirements. Additionally, designing
a simple and easy to use 3-D virtual environment is a factor that
leads to a higher user acceptability of a 3-D password system. The
choice of what authentication schemes will be part of the users 3-D
password reflects the users preferences and requirements. A user
who prefers to remember and recall a password might choose textual
and graphical passwords apart of their 3-D password. On the other
hand, users who have more difficulty with memory or recall might
prefer to choose smart cards or biometrics as part of their 3-D
password. Moreover, users who prefer to keep any kind of
biometrical data private might not interact with objects that
require biometric information. Therefore, it is the users choice
and decision to construct the desired and preferred 3-D
password.
FUTURE WORK
Textual passwords and token-based passwords are the most common
used authentication schemes. However, many different schemes have
been used in specific fields. Other schemes are under study yet
they have never been applied in the real world. The motivation of
this work is to have a scheme that has a huge password space while
also being a combination of any existing, or upcoming,
authentication schemes into one scheme. A 3D password gives the
user the choice of modeling his 3D password to contain any
authentication scheme that the user prefers. Users do not have to
provide their fingerprints if they do not wish to. Users do not
have to carry cards if they do not want to. Users have the choice
to model their 3D password according to their needs and their
preferences. A 3D passwords probable password space can be
reflected by the design of the three-dimensional virtual
environment, which is designed by the system administrator. The
three-dimensional virtual environment can contain any objects that
the administrator feels that the users are familiar with. For
example, football players can use a three-dimensional virtual
environment of a stadium where they can navigate and interact with
objects that they are familiar with. The 3D password is in its
infancy. A study on a large number of people is required. We are
looking at designing different three-dimensional virtual
environments that contain objects of all possible authentication
schemes. The main application domains of 3D Password are critical
systems and resources. Critical systems such as military
facilities, critical servers and highly classified areas can be
protected by 3D Password system with large three-dimensional
virtual environment. Moreover, a small three-dimensional virtual
environment can be used to protect less critical systems such as
handhelds, ATM's and operating system's logins. Acquiring the
knowledge of the probable distribution of a users 3D password might
show the practical strength of a 3D password. Moreover, finding a
solution for shoulder surfing attacks on 3D passwords and other
authentication schemes is also a field of study.
REFERENCES
A Novel 3D graphical password schema-Fawaz A Alsulaiman and
Abdulmotaleb El Saddik
Daniel V.Klein. Foiling the Cracker: A Survey of, and
Improvement to Passwords Security
Greg E. Blonder, Graphical Password, United State Patent
5559961
Rachna Dhamija, Adrian Perrig, Dj Vu: A User Study Using Images
for Authentication. 2000, Denver, Colorado, pages 45-58.