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Abstract—This paper describes a method of implementation
of Two Factor Authentication using Mobile handsets. This two
factor authentication is based on Time Synchronous
Authentication using the RFC1321 MD5 Message Digest
Algorithm of Epoch Time, Personal Identity Number (PIN)
and Init- Secret. The password generated would be One Time
Password (OTP) which would be valid for 60 seconds only
after which it expires and the user can not login through that
password. The proposed method has been implemented and
tested using J2ME OS based mobile Handsets. It can easily be
further extended to Android based Handsets also.
Index Terms—Mobile security, one time password, two
factor authentication
I. INTRODUCTION
Today Security Risks are of great concerns. Many
companies are comfortable with protecting their confidential
information and transactions with a password. A simple
password security may be effective for protecting non-
critical data. But memorizing passwords, administrative
issues and password hacking tools render a password-only
authentication policy inadequate for protecting confidential
information.
Authentication [1] is the act of establishing or confirming
something (or someone) as authentic, i.e. 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 it’s packaging and
labeling claims to be, or assuring that a computer program is
a trusted one.
There have been different strategies proposed for making
authentication mechanism more and more secure. There are
different ways by which the secure passwords can be
hacked such as Hashing, Guessing, Default Passwords,
Brute Force and Hashing. Generally, a password containing
both uppercase & lowercase characters, numbers and special
characters too; is a strong password and can never be
guessed. But still is not much secure way of authentication.
One way to strengthen your authentication policy is by
adding factors such as tokens, smart cards, digital
certificates and biometrics. The most common form of
multi-factor authentication is two-factor authentication
using a token or smart card as the second form of
identification.
For the Two Factor Authentication (T-FA), the user has
to carry a token/smart card which is really not feasible as for
Manuscript received February 25, 2012; revised April 26, 2012.
The authors are from ABV-Indian Institute of Information Technology
and Management, Gwalior (e-mail: singhal.manav@gmail.com;
stapaswi@iiitm.ac.in)
different organizations then he has to carry many Cards. So
Mobile Phones can be a good option as every person carries
a mobile handset these days. Mobile Phones now have
higher resolution cameras and near high definition video
with huge amounts of memory to enable storage of images
and music. Now the Internet can be browsed through your
handset and 3G and Wireless LAN connectivity is also
available.
In this paper, an attempt has been made to implement
Two Factor Authentication scheme using Software Tokens
so that the user can validate and authenticate his identity
using his Mobile Phones. In the next Section, background
about Two Factor Authentications is given, different types
of T-FA. Section III describe about Design Implementation.
And Section IV explains System Testing and then
Conclusion.
II. BACK GROUND
Authentication is generally a process which is required to
access the secure and confidential data. So the user is
required to establish his identity based on the different
factors. Here are the three mechanisms by which the user
authentication can be done are as given below: [2]
• Knowledge Factors
The first one is regarding what the requestor individually
knows as a secret.
For e.g. - Password or a Personal Identity Number (PIN)
• Ownership Factors
The second is regarding what the requesting owner
uniquely has.
For e.g. - Passport or an ID-card
• Inheritance Factors
The third one is regarding what the requesting bearer
individually is.
For e.g. - Biometric data, like a fingerprint or the face
geometry or the eye retina
Now the Two-factor authentication (T-FA) means using
any independent two of these authentication methods
(passport + Personal Identity Number (PIN) ) to increase the
assurance that the bearer has been authorized to access
secure systems. And Multi-factor authentication hence
means two or more of the authentication factors are required
for being authenticated to access the data.
Two-factor authentication is based on the concept of
“something you have” and “something you know”. Now a
days, the most common example in real life is the typical
ATM Banking Scenario – which combines something you
know (your password) and something you have (your ATM
Card) to prove your identity that who you are. Two –Factor
Authentication is vital for effective network security. Hence
Software Tokens Based Two Factor Authentication
Scheme
Manav Singhal and Shashikala Tapaswi
International Journal of Information and Electronics Engineering, Vol. 2, No. 3, May 2012
383

three types of T-FA are used generally in networks [3]:
1) Challenge Response Authentication
In this method, there are five steps defined in which the
user authenticates himself and proves his identity.
• Firstly the user enters his username and password.
• The Server sends an 8 digit challenge.
• Now the user enters the 8 digit challenge.
• 8-digit response is displayed on the token.
• Then the user enters the 8 digit response and thus
validated to access the data.
Challenge Response Method proceeds through a
laborious five steps process and it is much prone to user
error.
2) Event Synchronous Authentication
In this method, there are only three steps in which the
token code is based on the next number in the sequence, not
the random number generation scheme which makes it
much prone to the hacking.
• User activates the next token code by pushing the
button the token.
• User enters the username and passcode (the passcode is
an event produced token code and the user’s PIN).
• Then the server authenticates by matching the user
passcode with the server passcode (Server Passcode is
based on the next event in the sequence).
3) Time Synchronous Authentication
In this method also, we have three steps for the
authentication but here the difference is that both the user
and the server have the internal clocks that are synchronized
hence they are called time synchronous. And they also have
the identical seeds.
A seed is the starting values used by the random number
generation to create a pseudo random number.
• The user enters the username and Passcode (the
passcode is a 4 to 8 digit random token code and the
User’s PIN).
• The Server and the token create the token code by
combining seed record and current Greenwich Mean
Time.
• The Server authenticates the user passcode with the
server passcode and thus validated if found correct.
There are various advantages of the Time Synchronous
Authentication over the Event Synchronous and Challenge
Response Authentication.
• Security Concern
The Time Synchronous is much secured than the other
two because it is based on the token’s secret seed which we
can say is virtually hacker proof. The other two are less
sophisticated and prone to attacks.
• Easy Use
The time synchronous events steps are less while event
synchronous consists of three steps and challenge response
consists of five steps.
• Portability
Time Synchronous hardware tokens are extremely
portable because they are in not tied to the user’s desktop.
We can also choose from any number of factors that can be
easily integrated into the Palm devices and mobile phones.
RSA Tokens are based on the Time Synchronous and
hence are much safe and efficient and less vulnerable to
hacking attacks.
A security token may be a device that an authorized user
of computer services is given to ease authentication.
Security tokens are used to prove one's identity
electronically .We have two types of Tokens- Hardware
Token and Software Tokens.
The token is used in addition to or in place of a password
to prove that the customer is who they claim to be. The
token acts like an electronic key to access something.
Hardware tokens are typically small enough to be carried in
a pocket or purse and often are designed to attach to the
user's keychain. Software Tokens are type of security device
that may be used to authorize the use of computer services.
Software tokens are stored on a general-purpose electronic
device such as a desktop computer, laptop, PDA, or mobile
phone.
A new category of T-FA tools transforms the PC user's
mobile phone into a token device using SMS messaging, an
interactive telephone call, or via downloadable application
to a smart phone, which can display a six-digit security code
that changes every 30 seconds (assigned to a unique
credential ID for user registration).Since the user now
communicates over two channels, the mobile phone
becomes a two-factor, two-channel authentication
mechanism.
There are different commercial products available in the
market today such as RSA SecurID [4], Vasco’s DigiPass
[5], and PhoneFactor [6].
RSA SecurID two-factor authentication is based on
something you know (a password or PIN) and something
you have (an authenticator) providing a much more reliable
level of user authentication than reusable passwords. RSA
offers the enterprises a wide range of user authentication
options to help in positively identifying the users before
they interact with mission-critical data and applications.
VASCO’s Two-Factor Authentication technology
replaces insecure static passwords with strong, dynamic
OTP that can never be reused at future logins. This
enhancement increases access security without
compromising user convenience. Once activated, the end-
user enters and confirms their PIN each time a one-time
password is generated. VASCO VACMAN Controller
performs all OTP and signature validation functions for the
complete DIGIPASS product line, including DIGIPASS for
Mobile.
PhoneFactor adds a second factor of authentication to any
existing corporate or website login. The username and
password has to be entered first. Instantly, PhoneFactor
sends you a text message with a passcode. Simply reply to
the text message with the passcode to authenticate. This is
also a good Two Factor Authentication Product.
Here an attempt has been made to develop the software
tokens for mobile phones which are based on Time
Synchronous Authentication which would be efficient and
less vulnerable to hacking attacks.
III. EXPERIMENTAL DETAILS AND IMPLEMENTATION
In this paper, we propose a mobile based software token
that is supposed to replace the existing hardware based
384

tokens and computer-based tokens.
The system consists of two parts –
• Software installed on Client’s Mobile Phone.
• Server Software.
In this system, the One Time Password (OTP) would be
generated without connecting the client to the server. Here
Time Synchronous Authentication has been implemented.
The Server would be running separately and the user
would be generating the password based on some of the
factors which are unique to him. The Password so generated
would be valid for only certain duration of time. After that,
it will expire automatically. And after the expiry of the
token no login from that password and to login again, the
user has to generate another new password.
It is a free strong authentication solution for java capable
mobile devices like phones or PDAs. The Client Mobile
Phone must be java enabled (Nokia, Siemens, Motorola,
Sony, BlackBerry, etc.) because the Client side software is
developed in Java 2 Micro Edition (J2ME). And the Server
is also implemented in a Java 2 Enterprise Edition (J2EE)
using Servlets and Java Server Pages.
A. One Time Password
In order to make the system more and more secure, the
One Time Password algorithm must be such that it cannot
be guessed and should be safe from all sort of hacking
attacks.
Several factors can be guessed in order to generate the
OTP such as user’s mobile number but these factors can be
easily guessed and hence it would not be secure.
Secondly these factors must be common to both the
server and the client so that the password generated from the
factors at the client side must be matched with the password
generated by the server using those factors only. Since it is
time synchronous so the following factors are chosen:
1) Epoch Time
Here the current epoch time is generated in a 10 second
granularity. The Server and Client clock must be
synchronized then only it would work. Epoch Time would
ensure that the password generated would be unique every
time.
2) PIN
The second factor is PIN (Personal Identity Number)
which would be unique for every user. Hence it would also
serve the purpose of two factor authentication. This PIN for
each user would be stored in the database at the server side.
3) Init-Secret
The third factor is Initialization-Secret (Init-Secret). It is
also unique to every user. It is a 16-hex-digit secret that has
been created when the device was initialized. It would also
be stored in the database at the server side for each user. The
Init- Secret is not known to the user.
Authentication is based on two factors: a PIN known by
the user and the Init-Secret stored on the mobile device. To
compensate time differences, the server will accept
passwords from 3 minutes in the past to 3 minutes in the
future. The time should be synchronized with the client and
the server to ensure the correct password generated each
time. The above factors are taken together and they are
hashed using RFC1321- the MD-5 Message Digest
Algorithm [7].
B. Client Design
A J2ME program has been developed and installed on the
mobile phone to generate the One Time Password. The
program has an Interactive GUI so that the user can easily
handle this. The Software has been developed using Eclipse
as Integrated Development Environment (IDE) and it can
run on any Java enabled handset.
Firstly Load the MIDlet on the devices you plan to use.
Installation of the .jar and .jad file is vendor specific.
Usually java enabled phones come with some kind of
application installer for PCs that allows to install MIDlets
over IrDA or serial cable.
When the MIDlet is installed, run it. Now enter the PIN
to generate one time passwords, but to use them you will
need to initialize the device first and write the Init-Secret
into the appropriate user-record on the authentication server.
To initialize the token, press 0000. Enter an arbitrary
sequence of 25 keys as a random seed. The Init-Secret that
will be shown is not to be written down anywhere else but
the server itself.
It cannot be displayed again. If 0000 is pressed any time
later, the initialization string will change, i.e. the device will
be re-initialized. The initialization of a device should always
be done by the administrator of the authentication server,
not the user himself. A user does not need to know the Init-
Secret.
Fig. 1. Mobile screen displaying 8 digit pass code and init- secret code
The user is allowed to enter only his PIN. If he tries to
enter some other PIN, an error message would be displayed
giving unauthorized access. When the user enters the PIN,
the system concatenates the PIN, the Init-Secret and the
current epoch time and hashes it with RFC1321 MD5
Message Digest Algorithm.
Hence the hackers have to know both the PIN and Init
Secret in order to steal and crack the password. And the One
Time Password generated through the Software Token
would be valid for 60 seconds after which it expires. That is,
just after generation of password, the user must login within
60 seconds otherwise that password would expire and would
be of no use. Then he has to again generate the password.
C. Database Design
Here the database should be maintained at the server side.
385

A database design is needed at the server side in order to
store the information such as the Username, PIN and Init
Secret corresponding to each user.
The database will not be used to store the password as it
would not be secure but it would be used by the Server to
generate the password as the request comes to the server.
Hence the OTP algorithm would not be traced.
D. Server Design
A server would be implemented in the Organization in
order to generate the One Time Password (OTP). The server
consists of the database as described in the above section.
The Server is implemented using Java 2 Enterprise Edition
(J2EE) architecture. Initially the user has to register them at
the Organization and the Administrator will provide the
User his (PIN) and his Initialization Secret which he would
store in the Database at the Server and secondly he would
provide the mobile application to the user and the Init-
Secret would also be initialized on his handset and the
handset would be synchronized with the Server Clock.
So whenever the user would enter his PIN, the OTP
would be generated with the MD5 hash of the PIN, Init
Secret stored on the device and current epoch time. This
password would be valid only for 60 seconds after which it
expires. Now the user has to generate another password.
Whenever the request comes for the Password, the Server
generates the password for that particular PIN and Init-
Secret for the previous 60 seconds. If the password is
matched from one of those, the user is granted the access to
the System. The Init-Secret is not known to the user that is
just used by the user mobile handset to generate the OTP
and at the server side to generate the password.
And the Administrator can also generate the 16 hex digits
as the Init Secret (which is unique to every user) with this
system from the server side.
And in case the mobile phone is lost, the user has to
inform the Organization and then his account would be
disabled and hence the hacker/attacker would not be able to
break the security system. And if the hacker comes to know
even about the Init Secret by any chance, then also he does
not know the PIN of the user without which he cannot
generate the OTP. Hence it would be secure.
IV. SYSTEM TESTING
The Server was implemented using Java 2 Enterprise
Edition (J2EE) and the client side was developed using Java
2 Micro Edition and the application was installed on Nokia
5300 phone. And the SQL Server 2000 was used as the
database on the Server Side.
The experiment was done to check the chances of getting
same identical hash of two people. The database was filled
with 10 fake users’ information with the PIN unique to each
of them and the 10 different Init-Secrets were also filled.
The generated OTP was 8 characters long so that the brute
force attacks cannot also guess the OTP which can consist
of any letter or number.
The 10, 00,000 Passwords were generated for each user
for 10, 00,000 seconds of time and none of the single
password matched with each other. And the 10, 00,000
Passwords were also generated with different PINs of 10
fake users also and correspondingly no password matched
with one other. All OTPs were unique.
V. CONCLUSION
Now a days, using static passwords, as it is commonly
done for accessing the confidential data and information is
no more considered secure and safe. Hence Two Factor
Authentication becomes more and more popular. But on the
other hand, there are disadvantages of T-FA also. The
drawback of strong authentication is that every user has to
be provided with a token device. This can be quite
expensive. And hence the cost for the organization increases
as it has to provide its every user with the hardware token
for authentication which could be very expensive as to
provide the million users the token is not really practical.
Fortunately mobile phones that are capable of running
java applets are becoming more and more widely spread. It
stands to reason to use your mobile phone as an
authentication token. Hence Mobile Phones are a good
means of software tokens for using two factor
authentications.
This paper focuses on two factor authentication
implementation using mobile phones. The method has been
tested and found secure since it involves the factors that are
difficult to guess and hack.
REFERENCES
[1] E. Valente, 2009, Two-Factor Authentication [Online]
http://www.sans.org/reading_room/whitepapers/authentication/two-
factor-authentication-choose-one_33093Federal
[2] Financial Institutions Examination Council (2008). [Online]
"Authentication in an Internet Banking Environment" Available:
[3] http://www.ffiec.gov/pdf/authentication_guidance.pdf
[4] RSA SecurID Authentication, [Online]
http://www.opsec.com/solutions/partners/downloads/rsa_securid_roi.
pdf
[5] Mudge and Kingpin (January 2001), Initial Cryptanalysis of the RSA
SecurID Algorithm [Online] Available:
http://www.comms.engg.susx.ac.uk/fft/crypto/initial_securid_analysis
.pdf
[6] VASCO Digipass Family of Authentication Devices, [Online]
http://www.neocom.pl/dokumenty/VASCO/Whitepaper_Digipass.pdf
[7] M. Leiva-Gomez (December, 2011) PhoneFactor Tightens
Authentication in Smartphones and Tablets [Online] Available:
http://www.tmcnet.com/topics/articles/242225-phonefactor-tightens-
authentication-smartphones-tablets.htm
[8] R. Rivest (April 1992), RFC1321 MD5 Message Digest Algorithm,
MIT Laboratory for Computer Science and RSA Data Security, Inc.
[9] http://www.faqs.org/rfcs/rfc1321.html
Manav Singhal is pursuing Integrated Post Graduation in Information and
Communication Technology from ABV-Indian Institute of Information
Technology and Management, Gwalior. His areas of interests include
Mobile computing, Cloud Computing and had won many National awards
in Android Application Development. He won Best Application Awards in
Social and Business Category in Indian Android Developer Contest 2011,
Pune.
Shashikala Tapaswi is Professor in Information Technology Department,
Atal Bihari Vajpayee - Indian Institute of Information Technology and
Management, Gwalior, India. She has obtained her Ph.D. (Computer
Engineering) from Indian Institute of Technology, Roorkee, India, M.Tech
(Computer Science) from University of Delhi, India and B.E.(Electronics
Engineering) from Jiwaji University, Gwalior, India. Her primary research
areas of interest are Artificial Intelligence, Neural Networks, Fuzzy Logic,
Digital Image Processing, Computer Networks etc.
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