Now on Bluemix

IBM IDENTITY MIXER

Authentication without identification
NANOTECHNOLOGYCENTER

Eine Partnerschaft in Nanotechnologie von IBM Research und ETH Zürich

IBM Identity Mixer is a cryptographic protocol suitefor privacy-preserving authentication and transfer ofcertified attributes. It allows for user authentication
without collecting any personal data. Thus, nopersonal data is received that needs to be protected, managed, and treated according to complex legal regulations. Nevertheless, service
providers can rest assured that their access restrictions are fully satisfied.

IDENTITY SECURITY AND PRIVACY FOR
ELECTRONIC USER AUTHENTICATIONYour personal identity data was worth several hundred dollars on the black market 10 years ago. Today, it’s worth
pocket change. Why? Because it’s easier to steal this information than ever before.
As more pieces of our lives go online, we regularly have toauthenticate ourselves for service providers, including social
media tools and e-commerce sites. Today, identity authentication is realized by mirroring the paper-based processes
in the electronic realm, but this often exposes an excessive
amount of personal information. For example, when you
show your driver’s license to prove your age, you also unintentionally share your address.

PROTECTING PERSONAL INFORMATION
IN THE PAPER AGE
Because electronic information is much harder to control
and protect than information on paper, this praxis erodes
our privacy and puts us at risk. Indeed, the flow of information in today’s electronic networks is virtually impossible tofollow and assess. Thus, it is important that data is always
protected and kept secret and that disclosure is minimized
whenever possible.

Consider this fictional transaction: Alice, a movie buff, wants
to stream the classic film “Alice in Wonderland” from BestMovies, an online movie service. Before it will stream themovie, BestMovies requires proof that Alice satisfies thenecessary access control rules, i.e., that Alice has bought asubscription and is older than 12 years of age.
In the paper-based world, the clerk at BestMovies wouldtell Alice what proof is required, and Alice would present
her BestMovies subscription card and her driver’s license
or some other government-issued ID. The clerk would verify
the two documents for authenticity and specifically check
Alice’s birthdate. While the clerk would see all of her information, he would most likely forget shortly thereafter, assuming
he views hundreds of similar documents every day. Thus,
Alice’s privacy and information security is retained.

MOVING TOWARD DIGITAL SOLUTIONSThe same doesn’t hold true in the digital world. Like Neil
Armstrong’s footprints on the lunar surface, the information
will not be forgotten, but rather stored — most likely in thecloud, which is often poorly protected.
Unfortunately, the naïve transposition of the paper-based
world approach is exactly what is typically done: The identity
providers issue a credential to the users containing their attributes. Then, when authenticating with the credential, theuser has no choice but to transmit the full set of credentials to the provider no matter what data is being requested.
Apart from revealing more information than often necessary,users can be tracked across different service providers because of the uniqueness of their certificates. Some popular
examples of such technologies that follow this approach include X.509 client certificates as well as existing governmenteID solutions.
The second approach that is often employed requires theidentity provider to be online and involved in all of its users’
authentication transactions. While the issuer can certify only
those attributes that are explicitly required (which is good forprivacy), there’s a privacy bottleneck in the system that cantrack all its users’ transactions. From a security point of view,
this approach is not ideal: The identity provider needs to behighly available but also highly protected from cybercriminals, which are contradictory requirements.
Neither of these approaches is completely satisfactory froma privacy and security point of view because they both require users to reveal more information than necessary. Tosolve this, the team at IBM Research – Zurich developed
Identity Mixer. Identity Mixer uses advanced, provably secure cryptographic algorithms to authenticate users whileproviding only the minimally necessary information, withoutrevealing any collateral and unintended data, to simultaneously achieve both privacy and security.

HOW IDENTITY MIXER WORKS

This transformation is the third and probably most important difference to the traditional approaches. The presentation token consists only of the information that Alice needs
and is willing to reveal instead of the full set of attributes
contained in her credentials. Thus, the presentation token
would just contain the attributes “User is older than 12 according to a credential issued by the government” and “Userpossesses a subscription credential from BestMovies with anon-expired validity date.” The presentation token validates
with the public verification key. Then the verifier can checkthe validity of the token using the issuer’s verification key
with the cryptographic verification algorithm and learn only
the information about Alice that was specified in the presentation policy — nothing more.
Want to give Identity Mixer a spin? You only need a
Web browser to test the ultimate tool for both privacy
protection and security.

In its simplest form, Identity Mixer works similar to traditional
attribute-based credentials with a few crucial differences.
Each user has a single secret key but can have multiple public keys that correspond to it. In a way, this secret key is theuser’s secret identity, and users can derive as many public
identities from it as necessary. For example, Alice could use
one identity for BestMovies and another to pay her taxes
online. Each transaction gets a different public key, leaving
no privacy breadcrumbs.
Alice can get a certified attribute-credential such as an eID,a driver’s license or a membership card by sending one ofher public keys to the issuer of the desired credential. The
issuer will then sign that public key along with Alice’s attributes, which vouches for and sends the resulting credential back to Alice. Alice stores the received credential in her
digital wallet, which can run on her mobile phone, computer,another preferred device, or via a cloud-based wallet. This
process is conceptually identical to one of the X.509 attribute certificates, except Identity Mixer uses different, privacy-protecting cryptographic algorithms.
When Alice is requested to authenticate to a service — let’s
say she wants to stream “Alice in Wonderland” from BestMovies again — the service provider will send her a presentation policy stating the information needed to proceed. In
the example, the presentation policy would state BestMovies requires Alice to prove that she’s older than 12 according
to government-issued credentials and that she possesses
a valid subscription credential from BestMovies. This is thesecond difference to traditional approaches, where users
are typically asked to identify themselves in order for theservice provider to evaluate whether the user satisfies theaccess control policy.
Now, having received the presentation policy, Alice’s digitalwallet will offer her a choice of which credentials she canuse to satisfy it, or the wallet will point out which credentials she is missing. After Alice has selected the necessary
credentials, her wallet will use a cryptographic algorithm totransform her credentials into a presentation token, which
she can then send to BestMovies, the verifier.

Moreinformation:
For more
information:www.zurich.ibm.com/nanocenter
www.zurich.ibm.com/idemix

IDENTITY MIXER AS A SERVICE
Identity Mixer is available as an experimental service on theIBM Bluemix cloud development platform. This allows application developers to integrate authentication with Identity
Mixer in a way as simple as with openID.
Alternatively to Bluemix, application developers can use theopen source distribution of Identity Mixer.

MORE INFORMATION
Identity Mixer offers many more extended features than theones explained above, including exclusive pseudonyms,
multicredential tokens and designated inspectors. Learn
more about the privacy-preserving characteristics and dataminimizing strategies implemented on Identity Mixer’s website.
Project Website: www.zurich.ibm.com/idemix
Demo: idemixdemo.mybluemix.net
Bluemix: console.ng.bluemix.net/catalog/ibm-identity-mixer
Open Source: github.com/p2abcengine/p2abcengineContact: idemix@zurich.ibm.com