A Comparative Analysis of Identity Management
Md. Sadek Ferdous
School of Computing Science,
University of Glasgow, Glasgow, Scotland
School of Computing Science,
University of Glasgow, Glasgow, Scotland
Abstract— In this paper, we present a comparative analysis of a
few popular Identity Management Systems against a set of
requirements. Identity Management and Identity Management
Systems have gained significant attention in recent years with the
proliferation of different web-enabled and e-commerce services
leading to an extensive research on the field in the form of several
projects producing many standards, prototypes and application
models both in the academia and the industry. We have collected
and compiled different requirements from different sources to
profile an extensive set of requirements that are required for a
Privacy-Enhancing Identity Management System and presented
them in the form of a taxonomy. Then we have compared some
Identity Management Systems against those requirements and
presented them in a concise way to help readers find out instantly
which systems satisfy what requirements and thus help them to
choose the correct one to fit into their own scenarios.
Keywords- Identity Management; Identity Management
Systems; Security; Privacy; Privacy Enhancing Technologies
Currently there are literally thousands of websites around
the world providing a plethora of different services via the
Internet. These services require that users present their
identities for authentication in case they want to access those
services. To manage different users with their identities,
Identity Management (IdM, in short) was introduced initially
by the industry to facilitate online management of user
identities. Different research initiatives led to the creation of
different models and prototypes of Identity Management
Systems with each system satisfying its own sets of
requirements. Identifying what requirements are served by
which systems can be very challenging since the requirements
served by different IdM Systems are written in their respective
specifications and scattered among several documents. This
paper aims to aid in this regard by presenting a comparison
among different leading Identity Systems a concise way so
that any reader can instantly deduce which requirements are
fulfilled by those IdM Systems and which are not.
That said, this paper is organised as follows. We discuss the
related works in Section 2. In Section 3, we briefly describe our
chosen Identity Management Systems. We present a taxonomy
of requirements for an ideal Identity Management System and
provide a brief description of each requirement in Section 4.
We present our result of comparison among the selected
systems against that set of requirements in tabular formats as
well as discuss our findings and the limitation and strength of
our analysis in Section 5. Finally, we conclude in Section 6.
There are many Identity Management Systems currently
available. Requirements for each such system are usually
published in their respective specifications, documentations,
wiki pages, webpages or published papers. Several efforts to
converge those requirements from different sources can be
found in , , ,  and . We have extended their
works by adding a very few new requirements, subtracting
some and then restructuring several requirements so that a
concise taxonomy can be built.
A couple of examples for analysing existing Identity
Management Systems using a set of criteria can be found in
 and . A few Identity Management Systems such as
Microsoft .NET Passport, Liberty Alliance Architecture,
Novell DigitalMe, etc. and applications such as Mozilla 1.4
Navigator, Microsoft Outlook Express 6 SP1, CookieCooker,
etc. were analysed against a set of requirements. In current
settings, their work is almost outdated in the sense that many
of those systems are either functional in a restrictive way or
have been evolved into something new (e.g. Novell DigitalMe
transformed to the Bandit Project ). A more recent attempt
with the same objective can be found in  in which four
Identity Management Systems – Liberty Alliance
Architecture, Shibboleth, PRIME Architecture and Microsoft
CardSpace have been analysed against a set of requirements.
However, the current work provides the following
improvements over those works:
1. Our work provides and explains a comprehensive
taxonomy of requirements for an ideal Identity
Management in a more systematic way than any previous
2. Our work has compared 6 leading Identity Systems which
is 50% more than that of the last work.
3. Our work is more elaborative in the sense that the number
of requirements that were considered previously is far less
than that of this current work.
Published in the proceedings of the International Conference on High Performance Computing and
Simulation (HPCS), 2012
4. Moreover, our work is much more concise (327 pages in
 and 76 pages in ). Previous findings were published
in a descriptive way and readers would need to read
through a lengthy document to identify the missing
features. We have presented our findings in a tabular
format which is more illustrative and believe that it will
allow any reader to instantly identify which requirements
are met by which systems.
We have chosen six Identity Management Systems for our
comparative analysis which either have dominant positions in
Identity Management scenarios or introduced a novel concept
which is worth exploring.
A. Windows CardSpace
It was envisioned by Microsoft that an Identity Metasystem
- a system of systems - which is application agnostic and can
accommodate all existing technologies in a standard way can
provide a better solution to reduce many of Identity
Management problems. Windows CardSpace is their
developed Identity Metasystem . Unfortunately, Microsoft
has discontinued their CardSpace project. However, we have
opted to include it into our analysis because of its
fundamentally novel concept of Identity Metasystem. A brief
introduction to Windows CardSpace can be found in .
OpenID is a decentralised Identity Management System
which provides SSO solution for web services over the
Internet . It is a User-Centric technology and is being used
by many web service providers such as AOL, BBC, Google,
IBM, MySpace, Orange, PayPal, Verisign, LiveJournal,
Yahoo, etc. , . With more than 1 billion OpenID
enabled accounts and 9 million OpenID-enabled websites
OpenID is one of the wide-spread IdM Systems with huge
user-bases  and that is why it has been chosen for the
analysis. A brief introduction to OpenID can be found in .
Shibboleth is an open-source, provider-centric Federated
Identity Management middleware initiative by the Internet2
consortium and based on Security Assertion Markup
Language (SAML) standard . It is another widely adopted
leading Federated Identity Management System especially in
the Academia and that is why it has been chosen in this paper.
A brief introduction on Shibboleth Architecture can be found
D. Liberty Alliance Architecture
Liberty Alliance (LA, in short), established in 2001 and
currently known as Kantara Initiative, is a consortium of
commercial and non-commercial organisations aiming to
develop and provide open and interoperable standards for
Federated Identity Management . It has produced a
number of non-normative specifications to enable a secure and
privacy-friendly identity-enabled products and services mainly
based on SAML. A brief introduction regarding the LA
Architecture can be found in .
E. PRIME Architecture
The PRIME (Privacy and Identity Management for Europe)
Project was an EU and Swiss Government funded project
under FP6 Framework and was aimed to pursue research on
how to integrate different technical and non-technical issues of
Privacy Enhancing Technologies (PETs) with the Identity
Management scenarios and then to design and develop
prototypes of privacy-enhancing Identity Management
Systems . The result was the PRIME Architecture which
has strong focus on privacy. PRIME Architecture has been
explained in details in .
OAuth is one of the fastest growing community-based
specifications and has been designed to circumvent the
limitation of the delegation in the traditional service model
. The original specification, known as OAuth 1.0, was
finalised in April 2010 and is specified in RFC 5849 .
However, it went through a complete modification and evolved
to a new version called OAuth 2.0 is be finalised this year .
In this section we explain each requirement very briefly.
The requirements have been structured in the form a taxonomy
(Fig. 1) so that they can be used as comparable metrics for
comparing different systems.
A. Functional Requirements (FR)
The core services with respect to the Identity Management
Systems fall into this category.
1) Identity Administration (IA)
This group includes those requirements that are required to
administrate partial identities and other identity information.
a) Creating, updating and deleting Partial Identity and
its related information (CrUD).
An Identity Management System should allow any user
to create a new partial identity and then should offer the
service to update and, if a user wants, delete her existing
partial identity and identity information.
b) Usage of Pseudonyms (Psd)
To offer a better privacy, users should have the capability
to choose when to release her original partial identity and
when to use a Pseudonym. The Pseudonym should be
unlinkable to the original partial identity and the system
should offer the possibility of creating, updating and
deleting different Pseudonyms.
c) Credential Management(CM).
Credential is an important part of authentication and
authorisation; hence a system should have good
credential management capability.
d) Identity Recovery (IR)
Once a digital partial Identity has been stolen by an
intruder it needs to be recovered as soon as possible,
hence a system should specify an identity recovery
2) Representation & Dissemination (R&D)
This group enlists those requirements that are required for
representation and dissemination of identity data.
a) Representation (REP)
The effectiveness and usefulness of an IdM system
largely depends on how the identity data is represented
and visualised at the user-interface. It helps users to
select and choose correct partial identities, pseudonyms
and other attributes to be released to the communication
partner for a specific service.
b) Context Detection(CD)
Context detection can help to minimise data release and
thus can preserve privacy. Therefore, a system should
have the ability to detect the context.
c) Transaction Logging (TL)
Each transaction using an IdM System should be logged
for the purpose of history management.
3) Control (CTR)
This set of requirements allows users to control the data
flow between the user and the communication parties which
is essential for any User-centric approach as well as for
a) Policy Management (PM)
An IdM System should offer users the control over the
data flow by allowing users to choose the right
profile/partial identity/pseudonym with related attributes
for any given transaction. This can be effectively done
using different policies. Therefore, an IdM system should
have the ability to offer rule or policy management
b) GUI-based Representation (GUI-R)
A standard GUI-Based representation should be used to
help users to choose or create an appropriate partial
identity or pseudonym for any given transaction. If the
user selects an existing pseudonym, the GUI should
inform the user which entities that pseudonym has been
released to. This will help her to make an informed
c) Explicit Consent (EC)
An IdM System should inform the user via an intuitive
GUI about the data the system is releasing and ask for
her explicit consent before any release.
4) History Management (HM)
A good history management facility should display all
logged transactions in a user-friendly way. This will allow
users to check their data trail, i.e. what partial
identity/pseudonym and other attributes have been released
to what entity, when they have been released, if there is any
B. Security (SEC)
An IdM system can be used for accessing different services
ranging from participating in social network activities,
blogging and emailing to accessing Government services,
online banking, e-commerce activities, etc. There are different
levels of security for each of this service yet each activity
requires a minimum security guarantee to make sure that only
the authenticated user can access the requested service
1) Basic Security Mechanisms: Authentication (AUTH),
Confidentiality (CONF), Integrity (INTG) and Non-
The core mechanism of an IdM system is to ensure the
authenticity of a user. For simple web services, this can be
done using a user-id and password. For more secured
services such as financial or Government services,
biometrics, OTP (One-time password), hardware tokens, etc.
could be used. Confidentiality is to ensure that the
transmitted data between two parties is not disclosed to any
unauthorised entity. Integrity is to ensure that the
transmitted data is not altered during transmission. Non-
repudiation ensures that a user, once committed for a
transaction, cannot deny her commitment. Cryptographic
mechanisms can be used to ensure Confidentiality, Integrity
2) Multi-lateral security (MS)
When there are more than one party in an action, ensuring
security for all of them is the theme of Multi-lateral security.
An IdM system essentially involves more than one party and
that is why it is especially important to consider the issue of
multi-lateral security in IdM system. Multi-lateral security
assumes that each party minimally trusts each other where
each party can keep and enforce its own security goal .
C. Privacy (PRIV)
Currently, the privacy of a user, user identity and the
identity information are very important. Privacy Enhancing
Technologies (PETs) are the basic mechanism by which
privacy can be guaranteed. Configuring an IdM with the
principles of PET should ensure privacy protection
mechanisms integrated into the technology. A list of such
principles can be derived from . We are enlisting only
those requirements that can be used to ensure the privacy of a
user in the IdM setting.
1) Support of Anonymity (ANON) and Pseudonym (SAP)
A Privacy-aware IdM System should have a strong support
for Anonymity. Likewise, it should support the usage of
Pseudonym to ensure that users are unlinkable at the SP
when they want to do so. Privacy protection techniques
using various cryptographic methods can be used to achieve
2) User Empowering with Transparency (TR), Data
Control (DC) & User-controlled Linkability (UL) (UE, for
the whole property)
All the above mentioned privacy requirements will be in
vain if users are not in control of their data and have no idea
which data is released to which entity. We can empower the
user for managing their identities with the help of
Transparency (to let users be aware of what sort of personal
data is being transmitted to which entity and how they are
stored and processed at different parties), controlling the
data flow as well as with the ability to maintain a user-
3) Data Minimisation (DM)
Data minimisation can ensure that only the required data is
stored and processed at the SP and can guard against the
release of unnecessary yet sensitive personal data to
unauthorised parties which ultimately reduces the risk of
4) Remote Administration of User Policies (RAP)
In the traditional IdM System, users have no control over
their data once it has been released to other parties. One way
to enforce the control over released data is to allow users to
administer their data remotely.
5) Usage of Privacy Standard (UPS)
The Platform for Privacy Preferences (P3P) Project is a
W3C standard that allows websites to express their data
collection and management policies to their visitors in a
machine readable format . Using a privacy standard
such as P3P could allow users to express their privacy
requirements in a standard way.
D. Interoperability (IOP)
It will be crucial for any IdM system to have a good degree
of compatibility with other existing systems to make it a
hugely successful one.
E. Trustworthiness (TRW)
Users need to trust an IdM system as they will need to
provide a lot of their personal information. One the other hand,
a successful IdM System needs to gain the user's trust to exist.
In this section we are enlisting those factors that are required
to build and maintain a mutual trust between a user and an
1) Trust and Reputation Management (TRM)
In Multi-lateral scenarios like Identity Management, trust is
one of the central issues as the parties involved need to trust
each other in a certain way. This raises the question of how
trust issues can be managed properly. Trust is a complex
issue. There are so many different parameters and it takes
time to gain trust. However, a better implementation and a
good balance of usability, security and privacy could be a
decisive factor for users to place their trust on an IdM
system. Another related issue is the reputation of users in
scenarios like Amazon or eBay. In such settings, reputation
data is considered to be a personal data and therefore should
be protected like any personally identifying data. Trust data
are usually not of quantifying type and hence they cannot be
used as a comparable metric. Therefore, we will not include
it into our comparison.
2) Using Open Source Technology (UOST)
The use of open source technology helps to gain user trust.
When the source code of a system is released, it can validate
many of its security and privacy properties which in turn can
increase its trustworthiness.
3) Trusted Seals of Approval (TSA)
Security and privacy seals sometimes can be used to assert
that the system is secure or privacy-friendly according to a
standard. An example of a security seal is the Verizone
Certified to certify if a website is secure and an example of a
privacy seal is the P3P Seal to attest that a website complies
to the P3P Privacy policies.
4) Segregation of power (SoP)
Segregation of power is an important tool to gain trust
among users especially in multi-lateral scenarios like
Identity Management. Such property will ensure that no
single entity will have dominant position over other entities
so that it cannot abuse its power to monopolise a service. To
enable the segregation, it is necessary that the identity eco-
system and market itself is matured enough and users have
the ability to choose a specific entity based on their
5) Legal Protection (LP)
Legal protection is another way to achieve user-trust
especially in situation where financial transactions are
involved such as e-banking, e-auction, web-commerce, e-
taxation, etc. When users find they are legally protected
against attacks while using such services they will feel more
comfortable to get involved in transaction which in turn
increases the trustworthiness towards the system. Since the
legal requirement depends on a specific country or place and
the data cannot be quantified, we will not include it into our
F. Liability & Law enforcement (L&L).
Legal protection and ensuring liability is fundamentally
important for widespread usage and reputation of an IdM
system. The level and degree, again, depend on the context
and scenario in which an action is taking place. That's why it
should be adjustable by users who will fine tune the settings
according to the scenarios they are involved in. Some
requirements to ensure liability are given below.
1) Digital Evidence (DE)
Digital evidence can be used as the primary witnessing
source and would be necessary to claim liability or legal
protection in case of identity theft, reputation theft, warranty
or wrong delivery, tax fraud, unauthorised access, civil
action, etc. The mechanisms and how they can be integrated
into an IdM system are still an open issue and needs to be
2) Digital Signatures (DS)
Digital signature is the ultimate tool to ensure non-
repudiation especially in financial and citizen services. It
should be used when there is any chance of dispute,
especially in highly sensitive data transaction.
3) Data Retention (DR)
Data retention is the policy by which an organisation can
archive persistent data securely and in a privacy-friendly
way. It can be used in case any dispute arises. However, this
is opposite to the requirements of data minimisation which
states to store only the minimum amount of personal data.
How to find a good balance between these two is still an
G. Usability Requirements (UR).
Usability of a system determines not only the usefulness of
a system but also ensures the effectiveness of the security
mechanism. A usable system is easily adaptable and increases
the effectiveness of a system.
1) Comfortable UI (CUI)
User-interface is the primary point for users to get involved
with the system. It is the central component that allows
consent and check the data trail via the history functionality,
therefore it must host an intuitive, comfortable and easy to
2) Reducing System's Complexity (RSC)
A simply-presented system will less likely confuse a user
than a complex system. A system may be very complex in
nature. However, it is wise to hide this complexity from the
user with a simple and intuitive UI. Since there is no way to
quantify this requirement, it will not be used as a
H. Affordability (AFD)
As a general rule, the integration of an IdM system should
not be more expensive than the actual transaction; otherwise it
will drive the users away. It might be advantageous if a new
IdM system could bring in additional advantages by creating
the possibility for new business model and/or services. In this
group, we are enlisting those requirements that would be
helpful for any new IdM System to get wide-spread adoption.
1) Flexible Business Model (FBM)
A flexible yet attractive business model for any IdM System
is one of the essential properties to gain wide-spread
adoption. Other than users, an IdM System usually interacts
with business organisations. Therefore, a new IdM System
has to offer a substantial amount of incentives before any
organisation decides to get involved with the IdM System.
Since there is no way to quantify this requirement, it will not
be used as a comparable metric.
2) Power of Market (PoM)
The success of an IdM system ultimately depends on the
diversity of service it provides, the ease of availing those
services and the value-for-money for each service.
Therefore, the market that provides different services should
be a matured one with optimal cohesion between different
3) Open Source Building Blocks (OSBB)
This will not only enable to reduce the production as well as
adoption cost for an IdM system as well as help to gain user-
trust. The analysis of this requirement will be same as the
4) Subsidies for Development, Use, Operation, etc. (SDU)
Government can provide subsidies for development, use,
operation, etc. for an IdM system in case it is in line with the
Governmental aims and objectives. Since there is no way to
quantify this requirement, it will not be used as a
comparable metric and therefore we will not use it for
comparsing the systems.
5) Training and Education (T&E)
Training and education can be an effective way to educate
users to use the system effectively. This is especially true
for a new system when users are not familiar with the UI
6) Raising Awareness (RA)
Raising awareness helps people to be informed about the
possible attack scenarios that can be launched against an IdM
system or their identity data. This will help users to decide if
a particular action is invading her security and privacy.
We used the taxonomy of requirements listed above to
compare the selected Identity Management systems. To
compare them properly, we had to understand their inner
architectures and familiarise ourselves with their protocols.
Then we checked, one-by-one, if a single requirement was met
by a system. For this, we had to consult their protocol
descriptions, specification documents, corresponding wiki-
pages and sometimes development forums. We now present
our findings in Table I, II and III.
We have used the tick (√) mark, sometimes accompanied
with an explanation in brackets (), to indicate that an IdM
Systems satisfies a respective requirement and the character ‘
to indicate that the system does not satisfy the respective
requirement. However, there is one exception in T&E column
of the AFD requirement in Table 3, where tick (√) sign has
used to indicate if the user of the respective IdM system would
require any training and education to use it properly. The dash
(-) character has been used in cases where the requirement is
not of quantifying nature or a single ‘√’ or ‘
’ is not enough to
explain the analysis precisely. Another point of clarification
would be the usage of a ‘-’ for LA has been used to indicate
that being just a specification it has been difficult to find the
user-base of using any implementation of it and a ‘-’ for
PRIME has been used to indicate that being used by just a few
prototypes which were developed as a proof of concept, it is
very unlikely to have any reasonable number of users in the
case of PoM under AFD requirement in Table III. Additionally,
a ‘Large User Base’ for a discontinued system like CardSpace
is used to indicate that being a part of the Windows family
CardSpace is very likely to be already available to a large
number of users. In another non-functional requirement,
Comfortable UI (CUI), a (√) mark has been used to indicate
that this requirement was considered while designing and
developing the system and a (x) sign was used to indicate that
the requirement was completely ignored in the specification
and thereby not considered while developing the system.
As evident from the tables, excluding the entries with a ‘-’,
PRIME has met the maximum number of requirements (29 out
of 33) and is followed by CardSpace (22 out 33), Shibboleth
(18 out 33), OAuth (18 out of 33), OpenID (15 out 33) and LA
being the last one (11 out of 33). Other than that, we can
TABLE I. F
IA R&D CTR HM
CrUD Psd CM IR REP CD TL PM
X X X √
X X X
PRIME √ √
√ X X X X √ X
TABLE II. S
MS SAP UE DM RA UPS TRM
ANON Psd TR DC UL TRUST REPU
CardSpace √ √ X
√ √ X √ X X √ - -
OpenID √ √ X X √ √ X √ X X X - -
Shibboleth √ √ X √ √ √ X √ X X X - -
LA √ √ X √ √ √ X √ X X X - -
PRIME √ √ √ √ √ √ √ √ √ √ √ - -
X X √ - -
TABLE III. T
TRW L&L UR AFD
T TSA SoP LP DE DS DR CUI RSC FBM PoM OSBB SDU T&E RA
CardSpace X X X - X √ X √ - - Large User
Base X - √ √
OpenID √ X √ - X √ X X - - Large User
Base √ - √ √
Shibboleth √ X X - X √ X X - - Large User
Base √ - √ √
LA - X X - X √ X X - - - - - √ X
PRIME X √ √ - √ √ √ √ - - - X - √ √
OAuth √ X √ - X √ X X - - Large User
Base √ - √ X
interpret our findings presented in the tables in a number of
ways. We present here just a very few of them.
• With strong support for PETs, PRIME would have been the
ideal choice among them for a privacy-enhancing Identity
Management System. However, being only a research
project with a very few prototypes, it is uncertain currently
how it will be adopted in web-service scenarios. The
second suitable choice CardSpace being discontinued,
Shibboleth would be, presumably, the ideal choice in this
• Each Identity Management System has somewhat good
support for Security. However, many of them fail
substantially to meet many privacy requirements.
Therefore, it would be an interesting research topic to
investigate the ways many privacy requirements can be
integrated into those IdM Systems, especially, being the
two leading IdM Systems, in OAuth and Shibboleth.
• Graphically and functionality-wise, CardSpace is the most
feature-intensive. If otherwise missing privacy
requirements could be integrated, it would have been the
best choice for any circumstances.
• Context detection is another important requirement that has
been missing in most current IdM Systems. Context
detection could play a crucial role not only in data
minimisation but also in Mobile Identity Management
System where specific identity could be used based on the
environment the user is currently in. Policy Management
plays a major role in detecting context. Therefore, finding
the interplay between the context detection and policy
management and how these can be easily integrated into the
current Identity Management Systems could be another
interesting research topic.
• Presenting partial identity using InfoCard like in CardSpace
could be a viable candidate for managing identities in
mobile devices and again an interesting research question.
Google Wallet has already adopted a very similar approach
• It would be also useful to keep in mind that some
requirements, for example, functional, security and privacy
requirements comprise the core set of requirements and
carry more weights than others. Therefore, a system
satisfying more of these requirements should be considered
a better system than a system satisfying less of these core
requirements even though the first system may satisfy less
number of total requirements than the second system.
The above tables present a simple way of illustrating the
strengths and weaknesses of each Identity System and hence
identifying gaps in Identity Architectures. However, the over-
simplicity of the tabular format may obscure certain elements.
For example, the tables cannot be used to identify the
implementation of which system for a few type of
requirements is better than that of others in case all systems
satisfy those requirements. On the contrary, the tables would
perform flawlessly for identifying weaknesses for any
In this paper, we have analysed a few Identity Management
Systems against a set of requirements. We wanted to
investigate if the selected systems meet these requirements and
then present our findings in a tabular format so that any reader
can easily identify the strengths and weaknesses of those
systems. We have found that none of our selected Identity
Management Systems (a few of them are actually the leading
ones) can be declared as the ideal one which are functionally
rich, privacy-preserving yet usable. Especially the lacking of
different privacy requirements is worrisome. We have
presented a very few interpretations of our findings as well as
indicated some possible research directions based on our
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