Tuesday, October 28, 2014

Less is more

I attended GigaOM's Structure Connect conference in San Francisco last week. The event was great, lots of interesting discussions & panels.

I was in a 'Securing the IoT' breakout session where one of the GigaOM analysts made the assertion (paraphrasing)
Developers need better training on security, they need to take more responsibility for securing their applications.
This actually runs completely counter to what I've been seeing as the overarching trend around application security, namely that developers need to take (or even be given) less responsibility for securing their applications - not more.

If their app has to handle $$, do developers directly track currency exchange rates? No, they find an API that does that and so removes them from a task secondary to that of the application itself. The currency API abstracts away from the developer all the messiness - they make a simple REST call and get back a tidy bit of JSON to parse & use.

From the developers point of view, why would security be different? Do they want to deal with the specific details of supporting different authentication protocols, crypto etc. Or would they prefer to focus on adding features and functionality to their apps?

The trend towards lightening the security load for developers manifests in various ways

  • Social 'Login with X' SDKs - the large social providers make it as easy as they can for native application developers to hook into their identities. For instance, Facebook Login promises
The Facebook SDK for iOS provides various login experiences that your app can use to authenticate someone. This document includes all the information you need to know in order to implement Facebook login in your iOS app.
Google has the comparable the Google+ Sign-In, the documentation for which asserts
Avoid the hassle of creating your own authentication systemGoogle+ Sign-In mitigates data-breach risks and reduces the burden and costs of identity security. The Google authentication window creates a trusted link between you, your users, and their Google account.

  • REST gateways - many enterprise REST APIs are fronted by a gateway that intercepts incoming calls from clients and applies processing before delivering the call on to the actual API. The API developer need not directly deal with the authentication tokens attached to the original call, insulated from that burden by the gateway. Instead the gateway 
  • IDaaS - or Identity as a Service, is the trend of enterprises moving out to the Cloud certain identity & authentication mechanisms (just like many other enterprise functions are being outsourced). Rather than directly dealing with user provisioning, federation, or password vaulting etc the enterprise subscribes to the services of an IDaaS provider. The IDaaS takes on the full burden of the complexity of dealing with multiple protocols, business partners, customers, SaaS etc and offers back to the enterprise developer a much simpler integration proposition.
The above are all examples of freeing application developers from having to bear full responsibility for securing APIs & native applications. And last I checked, both will be relevant for the Internet of Things. Freed from the burden of security, IoT developers will be able to focus their attention where they should - namely creating new & interesting visual paradigms for my wearable step data.

Wednesday, October 08, 2014

Social Media 2 Factor authentication


A user can authenticate to a web application (or a federation server) by sending an update (tweet, Facebook update, etc) with a randomly generated hashtag previously delivered to the user in the login interface. 

The fundamental requirement is that 

  1. the user be able to demonstrate ownership of the social account previously connected to their account at the authentication server by including a challenge string in a tweet, update etc
  2. the authentication server be able to determine that a particular challenge string was added to a tweet, update etc associated with a particular social account 

User Experience

Step 1 :

User binds their social account to the authentication server

Screen Shot 2014-05-22 at 3.12.58 PM.png

Alternatively, the ‘binding’ could consist solely of the user telling the authentication server their Twitter handle.

Step 2:

Later, User visits login page

User logs in with first factor, ie password, or SSO

Login UI displays randomly generated challenge string
Screen Shot 2014-05-22 at 3.33.01 PM.png

Authentication server stores away challenge string against that user’s account

Alternatively, the challenge mechanism could be via Twitter, ie the authentication server sends the user a tweet, and the User response would be a RT.

Step 3:

User sends tweet , including challenge hashtag from Step 2

Screen Shot 2014-05-22 at 3.35.27 PM.png

The response format & channel will depend on the nature of the challenge and how the user’s social media account were bound to the account at the authentication server.

Step 4:

After displaying the hashtag challenge to the user , the authentication server polls the user’s tweet stream (or equivalent) on some schedule for a tweet (or post) containing the challenge hashtag.

If such a tweet is found within some time period, the authentication page displays successful login.


  1. The default would be for the user to manually type the challenge string into their tweet. Might it be possible for the authentication server to instead/also display a QR code, for the user to scan and so launch their mobile Twitter client with the tweet ready to send?
  2. Instead of a string, the challenge could consist of a link to a specific picture or some other media
  3. If the user has previously authorized other applications to be able to send tweets on their behalf, then those other applications would potentially be able to send a response tweet, but only if they were able to know the challenge. Consequently, the authentication model is likely only relevant for a 2nd factor, as having the user first authenticated with the other factor would prevent other applications from knowing the challenge string.
  4. if the authentication server were able to determine how many applications the user has granted the ability to tweet on their behalf, then conceivably it could factor that into it’s assessment of assurance
  5. There could be a viral component to the marketing of the authentication service, as the user’s followers would see the authentication tweets
  6. Is there a risk of violating Twitter ToS?

A symmetrical NAPPS model

The NAPPS WG in the OIDF is defining a framework for enabling SSO to native applications.

One challenge has been in supporting 3rd party native applications from large SaaS that already have an OAuth & token infrastructure (Salesforce as an example).

For this sort of SaaS, NAPPS has to allow the SaaS's existing OAuth AS to issue the token ultimately used by the app on the API calls.

The NAPPS spec is evolving to dealing with such applications in almost exactly the same way as it does native applications that call on-prem APIs built by the enterprise.

Fundamentally, for both categories of native applications, the enterprise AS issues to the Token Agent an identity token JWT, this handed to the application through the mobile OS bindings. The app exchanges this JWT for the desired access token to be used on API calls - the only difference is the AS at which the JWT is exchanged.

Local native apps
  1. app requests tokens of TA, includes generated nonce
  2. TA uses its RT to send request + nonce to AS
  3. AS returns PoP JWT
  4. TA hands over PoP JWT to app
  5. App exchanges JWT, shows PoP
  6. AS returns token(s) to app
3rd party native apps 
  1. app requests tokens of TA, includes generated nonce
  2. TA uses its RT to send request + nonce to AS1
  3. AS1 returns PoP JWT, targeted at AS2
  4. TA hands over PoP JWT to app
  5. App exchanges PoP JWT against AS2, shows PoP
  6. AS2 returns token(s) to app
Step 5 in the 3rd party sequence implies a federated trust model - the SaaS AS2 must be able to trust & validate the JWT issued by the enterprise AS1.

The above model is attractive for the symmetry it provides between both application categories.

Tuesday, October 07, 2014

As long as X is true .....

When my Samsung Gear watch is within BLE range of my Samsung S5, I need not enter my screen unlock pattern in order to get into the phone. The S5 interprets the proximity of the Gear as a proxy for my own proximity, and so deduces that it is myself handling the phone and not somebody else. 

This is an example of what appears to be an emerging model for authentication, which I’ll give the pretentious name of ‘conditional session persistence’ and characterize as

‘As long as X is true, no need to Y’

where ‘X’ is some condition - the continued state of which protects the user from having to perform ‘Y’, generally some sort of explicit login operation.

For my Gear & S5 use case, the X condition is ‘the Gear is within BLE range of the S5’ and the ‘Y’ is ‘demonstrate knowledge of secret unlock pattern to access phone’.

This authentication model is appearing elsewhere.

Screen Shot 2014-10-06 at 12.47.17 PM.pngThe Nymi wristband records the user’s ECG and sends it to a companion app on a paired device for it to be compared to the previously recorded ECG pattern. If the biometric comparison is successful, then the companion application responds back to the Nymi that it should unlock a previously registered crypto key and use that key to authenticate to resources and services. To ‘authenticate’ to the Nymi the user must touch a finger of the other hand to the top of the wristband - this creates an electrical loop that allows the ECG to be recorded. Once recorded and successfully compared, the ECG is not measured again, at least not until the wristband is removed from the user’s wrist. As long as the wristband stays on the user’s wrist the Nymi remains willing to assert the user’s identity by presenting the key (or presumably separate keys for different resources). Once removed from the wrist, then the user is required to re-authenticate once more via their ECG.

The Apple Watch is reported to use the same model.

Screen Shot 2014-10-06 at 12.03.26 PM.pngOn the back of the case, a ceramic cover with sapphire lenses1 protects a specially designed sensor that uses infrared and visible-light LEDs and photodiodes to detect your heart rate.

Via the 4 sensors on the back, the Watch will be able to determine when it is removed from the wrist after an initial authentication (by PIN it seems but it’s not inconceivable that it uses the heart rate as a biometric?). As long as the Watch stays on the user’s wrist the original authentication remains valid and the Watch can be used to, for instance, buy over-priced coffees from hipster barristas.

What is novel in this new model is of course the ‘As long as X is true’ clause - some sort of continuous check of the user’s context that serves to better bind them to the original authentication.  

Contrast this new model with traditional web-based authentication, in which, after the user presents some password (inevitably derived from their favourite sports teams name) the authentication server sets some session cookie

‘As long as T seconds haven’t expired, no need to Y’

In this model, nothing binds the user to the authenticated browser session and so prevents somebody else from hijacking that session - (which if of course is why those who (perversely) login to their banks and other sensitive resources from public kiosks are reminded to sign out when done).

Even in this new model, there will be differences in the certainty with which the persistence of X can be determined - the Nymi and Apple Watch, because they more tightly bind the user to the authenticating device, would likely offer more assurance than the Samsung Gear (I can take the Gear off my wrist and the S5 will be oblivious).

Of course, the ‘As long as X’ condition is only viable if there are local sensors able to monitor the state of X - whether Bluetooth proximity, or skin contact, or heart rate measurement, or future buttock-to-sofa contact etc. 

But fortunately the things that we are more and more surrounding ourselves with, even if primarily intended for some other purpose (think light bulbs, thermostats, and garage doors), will provide those sensors and so the ability to monitor all the different X’s we can think up.