Fingerprint Biometrics

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The other day I noticed one of my friends login to his laptop. I do this all the time, so that he logged in wasn't unusual, but how he did it, that caught my attention. He slid his finger on a small sensing area and after some delay he was logged in! No username and no password! This piqued my curiosity, put me on a research track. Here is what I discovered.

What are Biometrics?

When you login to your computer, security experts would say you authenticate. That is, you prove to the computer that you are indeed who you say you are. There are three ways you can normally prove who you are [2]:

  1. What you know
  2. What you have
  3. Who you are

When you login with a password, you are using the first form, what you know. If the password is kept secret and sufficiently hard to guess, when you enter your password the computer assumes it must really be you, because no one else would know the secret password. By this logic you are authenticated. There are other ways you can prove that you are who you say you are. When you purchase something with your credit card, or unlock your car door, you are normally authenticating with something you have. When someone checks your passport picture against what you look like, this is using two forms of proof: What you are, your face and what you have, namely the passport.

So what are Biometrics? From the word you might be able to deduce some of the meaning. The "bio" part means of or pertaining to biology. The "metrics" part relates to measurement. Put together biometrics it is the measurement of biological data. For authentication purposes a biometric is a physical characteristic that can be measured and then used to identify a specific individual.

When you use a "what you are" proof, it helps that you choose an attribute that is unique. If I used my height to prove that I am who I say I am, most of you would laugh. Why? Because there are lots of other people 6 feet 4 inches tall. For a strong identification, uniqueness matters.

How do fingerprint biometrics work?

Each fingerprint contains ridges in the skin which are detectable. These ridges make patterns which you can see with the naked eye. The ridge patterns can make loops, arches or whorls. In each fingerprint there are areas where one ridge changes, these points of change are called minutia. When a ridge ends, splits into two ridge, joins another ridge or creates a island; all of these features in a fingerprint are minutia. [10]

A fingerprint scanner detects the larger ridge patterns and records the following information about the minutia:

  1. Orientation - the direction the minutia is facing
  2. Spacial Frequency - how far apart specific features are located
  3. Curvature - the rate of orientation change
  4. Position - the (x, y) location relative to some fixed point

All of these can yield up to ideally 60 or 70 minutia for a single fingerprint. [10]

When a person first configures a scanner to use their fingerprint, this is called enrollment. This is a key time where strict process must be followed so as to avoid someone enrolling another's fingerprints as his or her own. In this process several fingerprints are recorded by the system and then an averaged template of the fingerprint is stored in the system. [10]

After enrollment, when a new fingerprint is supplied to the system, a statistical match is sought. If no match is discovered, the person is denied access. If a match is found, the person is granted access. Since biometric measurement can change slightly with each scan, determining a match is a probabilistic process. There is always a possibility that a valid fingerprint is rejected or an invalid fingerprint is determined to be good. [10]

What are the advantages and disadvantages?

To compare the relative merits of fingerprint as a biometric, we can considering the following properties of a good biometric [11, 6, 3]:

  1. Universality - each person has the characteristic
  2. Uniqueness - the characteristic is unique per person
  3. Permanence - characteristic remains the same over time
  4. Collectability - how easy is it to measure the characteristic
  5. Performance - accuracy, speed, and resource requirements
  6. Acceptability - culturally accepted by the population
  7. Circumvention - robust against fraudulent attacks

Universality

Fingerprints are largely universal. About 2% of the population can not use fingerprints due to skin damage or genetic factors.

Uniqueness

An important aspect of any biometric is that the characteristic be unique among all participants. Empirical evidence of fingerprints gathered since at least 1892, have found no two pairs of fingerprints that are identical, even between twins. [10] While this is reassuring, more recent research [13] indicates that the minutiae-based uniqueness as measured by fingerprint scanners may not be sufficient to determine individuality in every case.

Permanence

Fingerprints can be damaged and change due to manual labor or injuries.

Collectability

A key aspect of any biometric is the reliability of the measure coupled to the convenience of making the measurement. [10] Fingerprints are easy to collect and the systems today very inexpensive, around $20 per scanner if purchased in bulk.

Performance

Fingerprint recognition systems for large-scale deployments require a large amount of computational resources. For smaller populations the computational resources are smaller making this trade off allows for the current use in personal computers. Still compared with face recognition, for example, fingerprint scanners are more accurate, faster and require less computation and storage. Face recognition may seem very intuitive for humans, but the current mature computer systems are still far away from reliable face recognition in practice. [9]

Acceptability

Fingerprints are perhaps the most accepted biometric short of facial recognition. Still, the acceptance of biometric authentication technology depends on context, perceived benefit for the user and perceived privacy risks. [1]

Circumvention

Fingerprints are not impervious to attack, but using multiple finger scans can make the system harder to attack. ( see Myth Busters http://www.youtube.com/watch?v=MAfAVGES-Yc ) One method for improving the accuracy of biometric authentication systems is to enforce "two-factor authentication", that is one must authenticate by some biometric form as well as use a password or posses a token. [10] This additional factor can significantly harden the system.

Problematic Properties

Among the currently available biometrics, fingerprints have a large collection of positive characteristics. Some of the advantages of a biometric are that you don't have to remember passwords, don't have to worry about forgetting a password or smart card and it cannot be easily changed. [4] Because of these advantages systems have been developed for so called "One Touch Logon" [12] but in these systems one still makes significant trade offs between a password-based system and a fingerprint biometric based system. There are large trade offs between security and privacy [11] when using fingerprint biometrics.

Fingerprints have other problematic properties. They can be changed or damaged and some simply don't have fingerprints. Often because of these limitations fingerprint authentication systems have an alternate password based "back door" which can become the weakest link in the authentication system.

I think the biggest problem is that fingerprints are not very private, we leave fingerprints everywhere! Storing large amounts of fingerprint data in a safe way becomes a real challenge. If that data were exposed, criminals might devise a way to create fingerprints from the template data that fool fingerprint scanners. Biometrics in general are or can be unique identifiers, but they are not secrets. [7] Once a fingerprint is stolen, it's stolen for life! You can never get back to a secure situation! With a password or token system you can re-issue the token and invalidate the old token, or change the password. Not so with fingerprints! They are useful, but they are not keys. Keys need to be secret, random and easily updatable. Fingerprints are none of these things.

If fingerprint were to become the common authentication across different applications used for everything from logging onto your PC to accessing your bank account to opening your garage door, then value of stealing this information goes up significantly. At least with passwords you can spread the risk across different passwords for different services creating multiple barriers that must be overcome for full disclosure. With our fingerprints we have only ten of them.

References

[1] Heckle, R. R., Patrick, A. S., and Ozok, A. 2007. Perception and acceptance of fingerprint biometric technology. In Proceedings of the 3rd Symposium on Usable Privacy and Security (Pittsburgh, Pennsylvania, July 18 - 20, 2007). SOUPS '07, vol. 229. ACM, New York, NY, 153-154. DOI=http://doi.acm.org/10.1145/1280680.1280704 

[2] Guinier, D. 1990. Identification by biometrics. SIGSAC Rev. 8, 2 (May. 1990), 1-11. DOI=http://doi.acm.org/10.1145/101126.101127 

[3] Jain, A. K. and Ross, A. 2004. Multibiometric systems. Commun. ACM 47, 1 (Jan. 2004), 34-40. DOI=http://doi.acm.org/10.1145/962081.962102 

[4] Boatwright, M. and Luo, X. 2007. What do we know about biometrics authentication?. In Proceedings of the 4th Annual Conference on information Security Curriculum Development (Kennesaw, Georgia, September 28 - 28, 2007). InfoSecCD '07. ACM, New York, NY, 1-5. DOI=http://doi.acm.org/10.1145/1409908.1409942 

[5] Markowitz, J. A. 2000. Voice biometrics. Commun. ACM 43, 9 (Sep. 2000), 66-73. DOI=http://doi.acm.org/10.1145/348941.348995 

[6] Jain, A., Hong, L., and Pankanti, S. 2000. Biometric identification. Commun. ACM 43, 2 (Feb. 2000), 90-98. DOI=http://doi.acm.org/10.1145/328236.328110 

[7] Schneier, B. 1999. Inside risks: the uses and abuses of biometrics. Commun. ACM 42, 8 (Aug. 1999), 136. DOI=http://doi.acm.org/10.1145/310930.310988 

[8] Bergadano, F., Gunetti, D., and Picardi, C. 2002. User authentication through keystroke dynamics. ACM Trans. Inf. Syst. Secur. 5, 4 (Nov. 2002), 367-397. DOI=http://doi.acm.org/10.1145/581271.581272

[9] Zhao, W., Chellappa, R., Phillips, P. J., and Rosenfeld, A. 2003. Face recognition: A literature survey. ACM Comput. Surv. 35, 4 (Dec. 2003), 399-458. DOI=http://doi.acm.org/10.1145/954339.954342 

[10] Alfred C. Weaver, "Biometric Authentication," Computer, vol. 39, no. 2, pp. 96-97, Feb. 2006, doi:10.1109/MC.2006.47 http://doi.ieeecomputersociety.org/10.1109/MC.2006.47 

[11] Salil Prabhakar, Sharath Pankanti, Anil K. Jain, "Biometric Recognition: Security and Privacy Concerns," IEEE Security and Privacy, vol. 1, no. 2, pp. 33-42, Mar. 2003, doi:10.1109/MSECP.2003.1193209 http://doi.ieeecomputersociety.org/10.1109/MSECP.2003.1193209 

[12] Beomsoo Park, Sungjin Hong, Jaewook Oh, Heejo Lee, Yoojae Won, "One Touch Logon: Replacing Multiple Passwords with Single Fingerprint Recognition," cit,pp.163, Sixth IEEE International Conference on Computer and Information Technology (CIT'06), 2006 http://doi.ieeecomputersociety.org/10.1109/CIT.2006.128 

[13] Pankanti Sharath, Prabhakar Salil, Jain Anil K., "On the Individuality of Fingerprints (2002)," IEEE Transactions on Pattern Analysis and Machine Intelligence, http://biometrics.cse.msu.edu/cvpr2001_indiv.ps

Since the beginning of the Internet people have shared URLs with each other. Often the vehicle for sharing URLs was an email or a personal web page with favorite links. Today there are bookmarking websites where users share URLs, comment on them and rate them. [1] As the popularity of Twitter increases, more and more people are using Twitter to share URLs with each other. [2] The 140 character limit on communication with Twitter combined with the reality that many URLs are easily longer than 140 characters has given rise to more and more URL shortening services. While these services do a simple mapping, exchanging one short URL for a longer one, there are risks involved with trusting a third party to redirect you to a web page.

The basic idea for a URL shortening service is to exchange one URL that is short to another that is long. Typically the long URL is the desired destination. A person might send the short URL to a friend. When the short URL is clicked, the website looks up the longer URL and redirects the user to the longer URL. For example, suppose I just got an Amazon Kindle 2 and I wanted to share with my friends more information about it. Amazon typically has very long URLs. The URL for the Amazon Kindle 2 is as follows:

http://www.amazon.com/Kindle-Amazons-Wireless-Reading-Generation/dp/B00154JDAI/ref=amb_link_83624371_1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-1&pf_rd_r=0YPC2AH8155PQV3FWRPN&pf_rd_t=101&pf_rd_p=469942651&pf_rd_i=507846

That's 215 characters! I'll use this URL as the original URL with the following services to give you an ideas how they work:

bit.ly - http://bit.ly/

http://bit.ly/Z6eYE  19 characters

budURL - http://budurl.com/

http://budurl.com/bsfs  22 characters

eweri - http://eweri.com/

http://eweri.com/8rC  20 characters

hex.io - http://hex.io/

http://hex.io/ajz  17 characters

idek.net - http://idek.net/

http://idek.net/3kH  19 characters

is.gd - http://is.gd/

http://is.gd/lg7L  17 characters

lin.cr - http://lin.cr/

http://lin.cr/fvc  17 characters

POPrl - http://poprl.com/

http://poprl.com/Lm3  20 characters

snipurl - http://snipurl.com/

http://snipurl.com/cucc2  24 characters

tinyurl - http://tinyurl.com/

http://tinyurl.com/bngrky  25 characters

twurl - http://tweetburner.com/

http://twurl.nl/no316s  22 characters

urlBorg - http://urlborg.com/a/

http://ub0.cc/60/3G  19 characters

zi.ma - http://zi.ma/

http://zi.ma/65226b  19 characters

As you can see the original URL was 215 characters long, while the longest of the shortened URLs was only 25 characters long. I could post this shortened URL on Twitter and still have an expansive 115 characters left to comment on this URL. Perfect.

There are over 90 URL shortening services available online. A more complete list of URL shortening services is located at http://mashable.com/2008/01/08/url-shortening-services/.

Trusted or Untrusted

The most obvious risk associated with URL shortening is that it's difficult to know where the URL will take you, until you click it. The true destination of the URL is opaque. Often when I receive a dubious link via email, I hover my mouse over the URL, or view the HTML source to discover the real URL destination address and evaluate if I trust it enough to click. With a shortened URL, it's hard to know where it will take me, until I click it. Email Phishing scams are using URL shortening service for this very reason. [7]

Another problem with URL shortening is how it interacts with filters. A spam filter could use the URL in the past as one more hint that the email could be nefarious, but with a URL shortening service as the broker of URLs, the filter can't make any judgment about the URL. Many URL shortening services take spam complaints and will disable URLs if they are discovered to point to spam websites. [3] Some also proactively search their URLs for blacklisted websites and remove or disable these shortened URLs. [4]

Not just spam filters can be bypassed. Both Firefox and Google Chrome web browsers use Google Safe Browsing [5] a feature with warns users of malware or phishing sites. In the past using a shortened URL, instead of getting a warning message, users are sent directly to the dangerous web page. [6]

Less serious, but still problematic is using URL shortening services to hide the motive for an online review or recommendation. A seemingly objective review is tainted when readers discover that the author gets a monetary kick back for sending people to the reviewed product's site. Since shortened URLs hide the real URL they can be used to hide affiliate URLs and surreptitiously link to online stores. Most affiliate URLs are easy to spot, but when wrapped in a shortened URL, detection is more difficult. [8]

Another more remote, but still plausible problem with URL shortening is that should a URL shortening service become compromised, hacking one site would allow for redirecting popular shortened URLs to phishing or malware sites.

Getting More Transparent

Many URL shortening services have added some level of "see before you click" functionality. For example, any tinyurl can be prepended with the text "preview" in the URL and it will not redirect, but show the destination URL for inspection at tinyurl.com. Take the tinyurl above

http://tinyurl.com/bngrky

and modify it as follows:

http://preview.tinyurl.com/bngrky

While this adds characters to the URL, it allows the user to evaluate the URL before redirecting to the site. BudURL has an even more compact preview function. Just adding a '?' to the end of the URL will turn it into a preview URL.

http://budurl.com/bsfs  will auto redirect to the original URL

http://budurl.com/bsfs?  will preview the link first

Some of the services provide a little popup window that displays a picture of the webpage when you hover over the URL link.

Conclusion

A hacker or spammer is empowered by using a "benign" URL shortening service that everyone uses and everyone trusts. Once the click is made, a homographic attack may follow and will make it very difficult for a normal user to detect that they are being redirected to a phishing site. The real danger is that people have become habituated to trusting unknown links from their friends. This is dangerous because if their friend's account is compromised, it might not be their friend sending a link and the shortened URL will be clicked without concern.

An example of this propensity to click occurred 12 Feb 2009. One of my friends tweeted, "Don't Click: (link)". I was curious, but I didn't click the link. Next another posted the same thing, than another! It seemed fishy to me, and I later found out that the link presented a web page with another button that said, "Don't Click!" Naturally curious people, and trusting in their friend's recommendation, clicked the button and all of the sudden they noticed that they had in fact tweeted the same link though they never consented to doing so! It was the first socially engineered twitter virus. [9] While this virus was started as a joke, it spread extremely fast. [10] Luckily this social virus was harmless, but it reinforces how effective a socially engineered virus can be.

There are always trade off decisions to be made. In this case, the trade off is between the convenience of a short URL and the need for disclosure of a URL's destination.

References

[1] Tony Hammond, Timo Hannay, Ben Lund and Joanna Scott. - Social Bookmarking Tools (I): A General Review In: D-Lib Magazine 11, Nr. 4, 2005 http://www.dlib.org/dlib/april05/hammond/04hammond.html

[2] State of the Twittersphere - Q4 2008 Report - http://blog.hubspot.com/blog/tabid/6307/bid/4439/State-of-the-Twittersphere-Q4-2008-Report.aspx

[3] is.gd - Technical Information - http://is.gd/tech.php

[4] SURBL http://www.surbl.org/

[5] Google Safe Browsing for Firefox BETA http://www.google.com/tools/firefox/safebrowsing/  

[6] Finjan's Malicious Code Research Center, Evasive URL techniques, 25 Jan 2009. http://www.finjan.com/MCRCblog.aspx?EntryId=2153

[7] McGrath, D. Kevin, Gupta, Minaxi. Behind Phishing: An Examination of Phisher Modi Operandi. https://www.usenix.org/events/leet08/tech/full_papers/mcgrath/mcgrath_html/mcgrath_gupta.html

[8] Parker, Ryan J. Shortening (Affiliate) Links For Prettier Linking. 20 Feb 2007. http://www.ryanjparker.net/shortening-affiliate-links-for-prettier-linking/

[9] Korben. Petit cours de Twitt Jacking :-). 30 Jan 2009. http://www.korben.info/petit-cours-de-twitt-jacking.html

[10] Johnson, Clay. What is this Don't Click business? 12 Feb 2009. http://sunlightlabs.com/blog/2009/02/12/what-dont-click-business/

Creative Desires

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After reading Michael Lopp's excellent post The Makers of Things referencing the construction of the Brooklyn Bridge I was reminded of a poem. Not coincidentally, it's named The Bridge Builder and while I've mentioned it before, I think it bears repeating.

The Bridge Builder
by Will Allen Dromgoole

An old man, going a lone highway,
Came, at the evening, cold and gray,
To a chasm, vast, and deep, and wide,
Through which was flowing a sullen tide.

The old man crossed in the twilight dim;
The sullen stream had no fear for him;
But he turned, when safe on the other side,
And built a bridge to span the tide.

"Old man," said a fellow pilgrim, near,
"You are wasting strength with building here;
Your journey will end with the ending day;
You never again will pass this way;
You've crossed the chasm, deep and wide-
Why build you this bridge at the evening tide?"

The builder lifted his old gray head:
"Good friend, in the path I have come," he said,
"There followeth after me today,
A youth, whose feet must pass this way.

This chasm, that has been naught to me,
To that fair-haired youth may a pitfall be.
He, too, must cross in the twilight dim;
Good friend, I am building this bridge for him."

What I like most about this poem is that it touches on a reason we do the things we do. For example, when Washington Roebling became bedridden, why did he keep running the project rather than hand off the job to another? What was his motivation to carry on? We may never know, but for each of us, we can know our desires, our reasons. This is especially important because in the end we will get what we desire.

There are perhaps as many different motivations as there are people. Since we are complex beings, there are probably a multifaceted set of reasons behind our thoughts and actions. More subtle still, one reason may not even dominate in each context, every time. Some might work for a reward in money or fame. Others might do the things they do to impress others or to be a part of the "cool crowd". The desire to be well liked can be a powerful motivation for great effort. Some might create simply to provide for their temporal needs and for no other exalted reason. For them, the work they do is simply avoidance of pain. Others still create out of a sense of duty to their family, friends or traditions. Some simply want to see that they can do something and take joy in finishing a task well done. While some might laugh, others do the work they do out of a sense of love, a genuine desire to help. For me, when someone creates something, anything, it is always wonderful, but more impressive, are the reasons coupled with the creation. 

Another aspect to creative motivation is that different desires yield different results and staying power. When you are called to lead a team, (or more difficult lead yourself alone) to work through the impossible, you can not be ignorant of the motivations needed commensurate with the work at hand. However, discerning these delicate human desires and their creative force can be a powerful tool when confronted with the problems and setbacks that will undoubtedly come.

Ultimately we choose. We choose to build, to create, to do the things we desire. We make the little choices, as small as lifting a bucket full of mud from a river bottom and as large as trusting that a bridge pier will stand the test of time. Small and big and everything in between reveal in us our inner creativity and deepest desires. Recognizing this brings a somber circumspection to the tasks of each day. The wonderful thing is that it's all in there, in each of us, to quote, "Trust me when I say that I can close my eyes and see the end result, and when you can see it, too, you will be amazed."

Specifying Performance

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When you design a software product or feature you need to consider not only what the software will do, but also how it will interact with the user. The functional requirements for the software typically refer to what the software does. Nonfunctional requirements clarify the parameters for how the software will meet the functional requirements. Common nonfunctional requirements include things like reliability, availability, security, safety, usability, programmability, maintainability and performance. All of these are important, but your software's performance will have a disproportionate impact on how your software will feel when people use it. I think Apple put it well in their Apple Human Interface Guidelines:

"Performance is the perceived measure of how fast or efficient your software is and it is critical to the success of all software. If your software seems slow, users may be less inclined to buy it. Even software that uses the most optimal algorithms may seem slow if it spends more time processing data than responding to the user. ... Remember that the perception of performance is informed by two things: The speed with which an application processes data and performs operations and the speed with which the application responds to the user." [1]

While performance is one of the most important nonfunctional requirements, it's often the most difficult to define. For new features it's difficult to know where to set the performance goal because there's not always some similar functionality to compare it against. Further, how would you define "slow" or "fast" in an objective and verifiable way? Confronted with this problem most software engineers simply skip this section of requirements with the justification, "If it's too slow, I'll see it and we'll fix it then. I know slow when I see it." If performance is specified, often some arbitrary time limit is set with little reasoning behind the performance goal.

Failing to specify reasonable performance requirements makes it very difficult to verify that your software is actually meeting your users' performance expectations. And what are these user expectations any way? How can you determine what makes one piece of software fast and the other slow? Understanding a little about the psychology of time perception can answer these questions. Armed with this understanding you can specify, design and build for performance from the very beginning and this tremendously improves the chances of a high performance solution. 

Responsiveness

Any human computer interaction can be thought of as a conversation between the human and the computer. The user does something and the software and hardware respond to that request. The time it takes the system to respond to the request of the user is the system response time.

There as been quite a bit of research done in the area of system response times. In 1968 R. B. Miller wrote a paper titled "Response Time in Man-Computer Conversational Transactions." [2] The Department of Defense created MIL-STD 1472F [3] a 219-page document titled "Department of Defense Criteria Standard: Human Engineering (revision F)" which describes many of the non-functional requirement standards for use in the military. Sponsored by the US Air Force the MITRE Corporation published in 1968 a document titled "Guidelines for Designing User Interface Software". [4] In 1996 the Department of Defense created an eight-volume work entitled "Technical Architecture Framework for Information Management (TAFIM)" and the last volume in this work includes guidelines for response times [5].

All of these standards for system response times include descriptions of types or classes of actions by the user and the guidance for the acceptable response time by the system. More recently Steven C. Seow published a book titled "Designing and Engineering Time". [6] This excellent book describes in detail some of the important considerations for defining appropriate response times and simplifies the combined recommendations of previous research into a simple framework. The general framework Seow suggests is as follows:

Instantaneous (0.1 to 0.2 seconds)
Immediate (0.5 to 1.0 seconds)
Continuous (2 to 5 seconds)
Captive (7 to 10 seconds)

You use these performance guidelines by asking yourself the question: For this feature, what is the users expectation for response time? Is the user expecting an instantaneous response? If so, then you know your software should respond within 0.1 to 0.2 seconds.

So what is slow? These response time categories provide a powerful answer to this question. Slow is when a user expects an immediate response, within 0.5 to 1.0 seconds, and they get a continuous response, somewhere from 2 to 5 seconds! Slow is when a user expects an instantaneous response, within 0.1 to 0.2 seconds, and they get an immediate response, somewhere from 0.5 to 1.0 seconds!

Note: Can a response be too fast? Yes, a good example of this too fast response is when a user starts a software installation and the install completes immediately. The reality of the response time doesn't conform to their expectation and will cause the user to think the install didn't work properly.

Performance is a perceived reality based on the conversation between the human and the computer. As Qui-Gon Jinn said to Anakin, "Remember: Your focus determines your reality." [7] This is especially true with software performance. What the user is focused on is not the performance of your application, at least not initially. They are focused on doing something with your application as the means to an end. When the application is responding to their commands appropriately, this becomes a natural conversation between the human and the computer and turns into a state of flow where the user is happy and productive. The challenge for a software developer is to maximize the probability that your software will disappear from the focus as they are enabled to enter that zone of creativity. Response times that are too fast or too slow and disrupt the user's state of flow degrade the user experience.

Sadly, brilliant architecture doesn't matter if the user feels like you're wasting their time or something is wrong. They will feel like something is wrong if you don't ensure that the system responds within the expected time frame. Identifying the areas in your software that conflict with a user's expectations is the first step in making your software feel fast and responsive. Putting the user at the center of this question is the key to building high performance software. Let's dive in to what each of these response time categories means in detail.

Note: Steven C. Seow has long studied the distortion of time perception. I met him shortly after he joined Microsoft. Recently he has released his first book, "Designing and Engineering Time". It's a fantastic book, one I own and highly recommend. While I try to summarize some of his ideas on responsiveness, he goes into much more detail in his book and I recommend going there for a more complete understanding.

Instantaneous

When a user moves a mouse or clicks a button the expectation is that the software will respond instantaneously, that is at least within 0.1 to 0.2 seconds. The easiest way to determine if a part of your software falls into this category is if the interaction mimics some object in the physical world that also has an instantaneous response. Most forms of user input fall into this category. Clicking a menu and waiting for it to drop down or dragging a slider are all examples of where an instantaneous response is expected. If you have ever opened your Mac laptop from sleep, and tried to click the Airport menu and had it hesitate and then display, you have experienced the problem where the expectation for an instantaneous response is not fulfilled.

Immediate

The best example of an immediate response, between 0.5 and 1.0 seconds, is scrolling a window. The user's mental model is that the data has already been "loaded" so telling the computer to display a different section carries the expectation that it should occur immediately. The detailed operations behind any user interaction are hidden from the user. For example, fetching and rendering large documents often involve paging in and out memory, but this is invisible to the user. When they move to the next page they expect the response to be immediate since their mental model tells them all the "hard work" as been done when the document was first loaded. The expectation is what matters. In this realm of response times, the key is to communicate to the user that the request or command has been received and if the action is simple, a complete response is returned in less than 1 second. Animation can go a long way in avoiding awkward pauses in the response between the system and the user. The iPhone's checkered back screen when scrolling a web page is a good example of immediate feedback, while dealing with real hardware and software constraints.

Continuous

Unless the user is expecting an instantaneous or immediate response there is generally recognition that the computer needs to "think" about doing stuff. Miller wrote:

If you address another human being, you expect some communicative response within x seconds-perhaps two to four seconds. ... In conversation of any kind between humans, silences of more than four seconds become embarrassing because they imply a breaking of the thread of communication. [2]

In the continuous category, between 2 and 5 seconds, it can be helpful and calming to let the user know that the computer is "thinking." Progress bars are often helpful in this case, but not required. On the Mac, both Keynote and PowerPoint use progress bars to inform the user that work is being done when loading documents. When the user asks your software to do something moderately complex, the continuous response will be the expectation.

Captive

In the 7 to 10 second response range, users need to see real progress and visual response. I like to think of this as the captive audience range. You will have a user paying attention to what's going on in this range, but anything that takes longer than this, they'll move on to something else and come back to see progress later. A good example of this is downloading a fast start movie online. The user's attention span is about 10 seconds, so if your process takes longer than that you'll need to provide significant visual feedback to what's going on and be certain to give the user the ability to move on to other things.

The Process of Setting Performance Goals

For each user interaction in your software ask yourself if the user is expecting an Instantaneous response, (0.1 to 0.2 seconds) an Immediate response (0.5 to 1.0 seconds) a Continuous (2 to 5 seconds) or a Captive response (7 to 10 seconds). This will set the range of response times for that part of the system. Use the appropriate response time range as your performance goal. This will give the developer a basic understanding of where the performance for that feature needs to be and allow the tester to test for system responsiveness from the beginning.

Most features are easily classified into one of the four categories, but sometimes it's hard to tell. In this case usability studies can help inform you if your best guess was wrong. 

Conclusion

When you need to choose which part of your application to focus on speeding up, understanding where and why users will perceive performance problems is key. You can't and shouldn't optimize everything. Remember, perception is reality. No mater what your metrics say, if the user thinks your application is slow, it is.

Objectively measured durations don't mean anything without a corresponding benchmark that shows what a user expects. They will judge your software against their expectations. You need to identify what kind of expectations the user has for each stimulus and response in your application and make your software response times meet these expectations. Users have four general categories of expectations: Instantaneous (0.1 to 0.2 seconds), Immediate (0.5 to 1.0 seconds), Continuous (2 to 5 seconds) and Captive (7 to 10 seconds). The more areas in your application where the users expectation are met with your application's actual response the faster the application will feel.

Maister's First Law of Service [8] states that the key to satisfaction is the delta between what was expected and what was perceived. If the perception is that your software performs better than expected, satisfaction will be high, but if the perception is that your software performs worse than expected, satisfaction drops. Perceived durations and actual durations along with an understanding of the users' tolerance for both will allow you to carefully design software to meet and exceed user expectations.

References

[1] Apple (2008). Apple Human Interface Guidelines. Available online at http://developer.apple.com/documentation/UserExperience/Conceptual/AppleHIGuidelines/OSXHIGuidelines.pdf page 31, 57

[2] Miller, R. B. (1968). Response time in man-computer conversational transaction. Fall Joint Computer Conference U.S.A. 267-277.

[3] Department of Defense Design Criteria Standard: Human Engineering. MIL-STD 1472F. Available online at http://hfetag.dtic.mil/docs-hfs/mil-std-1472f.pdf

[4] Smith, S. L. and J. N. Mosier (1986). Guidelines for Designing User Interface Software: ESD-TR-86-278. Bedford, MA: The MITRE Corporation.

[5] Department of Defense Technical Architecture Framework for Information Management (TAFIM). Volume 8: DoD Human Computer Interface Style Guide.

[6] S.C. Seow, Designing and Engineering Time: The Psychology of Time Perception in Software, Addison-Wesley Professional, 2008.

[7] Star Wars - Episode I, The Phantom Menace, 20th Century Fox, 2005.

[8] Maister, D. H. (1985). The psychology of waiting lines. In Czepiel (Ed.), The Service Encounter. Lexington, MA: Lexington Books. 113-123.

Google Chrome and Gears

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Google is now building their own web browser named Chrome, based on the WebKit rendering engine and a beta version for Windows is currently available. They've put up some great comics that do a great job of introducing the new browser and some videos explaining some of the changes they've made.

I've always found Google applications on my Mac to be a bit out of place. Maybe it's part of the design they are going for, but even today, when I use their online apps, like Gmail, or desktop applications like Google Earth, they work well, but beautiful they are not. They are blocky, text heavy, lowest common denominator type of UIs. It's always felt to me like they didn't quite "get it" when it comes to blending into the platform and learning to be a "good citizen" on the user's platform of choice.

Today, it's clear to me why I've felt this way: Google isn't interested at all in "being a citizen" or part of a platform, they are interested in being the platform. If you look at the way Chrome is designed, it's not so much designed to be a good browser, as much as it is a good operating system for web applications. Google's desire is very much the same as Microsoft's, except abstracted a little higher up the stack. They want to own the platform upon which web applications are built, just like Microsoft wants to own the platform upon which desktop applications are built. This game of disintermediation seems to never end, but this time, what can Microsoft do? Or anyone else for that matter?

This is not to say that Google's success criteria for Chrome is market share. I think what they are trying to do is have a more direct hand in guiding and shaping the web app platform and raising it to a level that best fits their desires and needs. Google will be successful if in the future developers see no downside to developing a web app versus a traditional desktop application, but in-fact see a sizable upside to taking the web app route. For end users success will be when the "Omnibar" becomes the default interaction mechanism, the place they go to first and installers become a thing of the past.

Maybe that's why I think Google's stuff looks kind of basic. They are to the current web platform what command line terminals were to the earlier personal computer platform. The basics, from which great things are built.
Everyone knows that the iPhone is an expensive bit of technology, but overall its success has shown that it's "worth it" in most places. What's interesting is that the iPhone is NOT having much success in India, where the monthly payment can't hope to subsidize the costly phone. Says Niti Bhan:

I'll say it again about the iPhone, business models need to be designed as much as the product for the market they are intended to operate in, taking the nuances of culture, socioeconomic development as well as the customer's mindset into account. That is, as Neelakantan puts it so pithily in his most recent comment, "know your customer" and that's something we know that Apple hasn't quite managed to do yet. After all, their design success is primarily through designing for themselves.

Having the same marketing story for every market world wide certainly has its advantages, but perhaps there's room for some diversity here. Then again, Apple may have its current focus on affluent markets and plan to customize and optimize things later.

Painted on the Inside

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My son and I recently visited the Legacy Flight Museum in Rexburg, Idaho. This is an aviation museum that they call a "living museum" because everything on display actually flies regularly! In fact, we see them flying over our house on a weekly basis.

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When we entered the office area of the hanger to start the guided tour, I saw a large table full of model airplane parts, plans, glue and paints.

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The museum is open 9 AM to 5 PM, Monday through Saturday in the summer, even so, there are times when there are no visitors. During the down time some of the curators and tour guides build model airplanes. When we were there, we met one of them, his name was George Howard. After the tour, I asked him about his hobby, and he showed off his model airplanes.

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He had a P-61 Black Widow, a B-25 Mitchell, a B-17 Flying Fortress, a B-29 Superfortress, a Convair B-36 as well as many other smaller fighters and planes whose names I don't remember. It turns out he teaches model building classes in the museum from time to time. You could tell by talking to him that he loves the planes. While we were talking about the models, he said this, "If you'll look into the cockpit, you can see the dashboard is all painted. Every plane is like that, even at 1/32nd scale. The propellers all work, and the wheels on the landing gear work and even the ordinance hooks release." Gingerly putting down one of his prized planes he picked up the B-29 Superfortress and continued, "This plane has an office and bunks and they're all painted on the inside, if you could see them, you'd see all the detail. You know when you start cutting corners, who knows where you'll stop? I try to go all the way."

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This idea of doing something "on the inside" bespeaks a level of integrity and love for quality work that is rare in any line of work, but especially in software. The counter arguments abound: Why the extra time and effort? Why should we be doing something that will seldom if ever be seen or appreciated by the end user? Where's the customer use case? What's the business case? Who cares? How will this really make a difference for the customer? Like painting on the inside of a model airplane, the answer is, of course, that they will not know, but you will. As the builder, designer and developer of the product, you will know that it's painted on the inside.

Clockwork

There's a long tradition of quality that can't be seen with time pieces, especially small ones. If you have ever opened a clock, or observed as an expert watchmaker opened the case, you know of the intricate gears and precise beauty inside. While the watch cover almost always conceals this internal and hidden quality workmanship, it was seen by enough people that it became the common standard for exact, reliable and good engineering. People would say a system was good when it "worked like clockwork." Some modern clock manufacturers have chosen to put on display the internals of their clockwork. This is an interesting way to allow the user a window into the complex and detailed world of gears, springs and latches that make the whole product work.

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Now, one might again argue, "Where is the user scenario? How does this actually make it better for the user? But, of course, there is no user scenario. Functionally, the clock is the same with or without the glass panel. One might even argue that with the gears exposed it is harder to read the time! But the feelings of the user about the purchased piece of engineering are much, much different. There's a feeling of trust that someone took the time to make all of those inscrutable pieces fit together and work so that he or she could do something rather simple, like keep track of time. There's also a sense of pride in owning such a fine bit of complexity.

My favorite "marketing use" for this kind of watch is where the manufacturer has put the window on the back of the wrist watch only. This way the watch looks normal in every other respect, except when the user puts on the watch or takes it off. If someone comments on the watch, there's a natural path for the owner to say, "Thanks, but look at this..." and pull off the watch and show all the insides clicking and moving just like, clockwork. "Cool huh?" "Yeah, it's beautiful."

The integrity of design and beauty was always there. Functionally, there is no new "feature" in the watch. But if you call love for the product and desire for superb quality, inside and out, a feature, well then, this kind of product has it.

Trophy Box

This kind of care for the inside and unseen workings applies just as much to what you do as to how you do it. For as long as I can remember, part of the tradition for shipping software at Microsoft has been that you get a "Trophy Box" or a copy of the shipping software, in the shrink wrap for you to use or just keep on display. Many at Microsoft would simply keep each one of these on a shelf over time accumulating physical reminders of products they had helped to produce. This tradition was followed for Mac Office 2008 as well, but for the first time in MacBU history it was different:

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The Mac Office 2008: The Special Launch Edition

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The front of the box

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The back of the box

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Craig's Note

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The inner sleeve

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The Office Pen: Proof that MacBU has produced multi-touch hardware. ;-)

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Nice touch on the Office logo.

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Not just Office, but Expression Media too!

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The CDs: Nice "ether" swoosh stuff, eh?

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Nicely etched Office ship date on the back of the box along with the edition number.

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The correct number of Stickies! Well played!

Now, no one in MacBU will deny that the Office 2008 product cycle was a tough one, and a box like this in no way makes up for all the difficulties. Certainly it doesn't "help sales", but it does mean something to those on the inside. It says something to the employees, who are your first customers. It says, "You're worth taking a little extra time and a little extra care." This kind of message may not be something accountants can tabulate in the asset column, but its value is there just the same.

The Apple Paperclip

A few months ago, my wife's iPhone stopped working. We called Apple and since we were nowhere near an Apple Store the lady on the phone said she would send us a box to send the iPhone back to Apple for repairs. This kind of process, while less ideal than dropping the phone off at an Apple Store and walking out with a loaner phone, is something I've come to expect from Apple's customer support. When we got the box here's what it looked like:

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The iPhone repair box we received.

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Simple directions on the lid of the box

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3 steps: Help is here. Back it up. Pack it up. Note to Apple: Apology accepted.

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The "iPhone Service Guide", step 1: Don't lose this.

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The Real iPhone repair box.

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The white box is padded, with a padded sleeve for the iPhone. And tape.

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The foam case. The red stripe removes to expose adhesive for the flap.

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Tape strips for closing the box included.

Let me review the situation: Apple sends a box with thick foam padding and return postage paid to send your iPhone to Apple to repair. General overview of the process, backup and packing is provided, as well as detailed instructions. Inside the thick foam is another box, also with foam padding, and inside this box is a foam sleeve with a flap to fully surround your iPhone with protective padding for the trip. Tape is included so you don't even need to find packing tape to get the job done!

Look at all the padding and packaging there to protect your precious iPhone! What does it say to you as the customer about how Apple feels about your iPhone? What does that say to you about how important your iPhone should be to you? But the most distinctly "Apple touch" in the whole package is the Apple SIM Ejector Tool that is included:

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An individually packaged paperclip! Did they need to do that? How much did that cost them? Couldn't they just trust that folks could find a paperclip around the house or office? Yes they could have, but they didn't. With the desire to make the the whole process as painless as possible they made a negative repair experience into a positive, brand building and trust building one.

I'm sure there are other examples, but it's this care for the little details, things on the inside, bits that are often unseen, that can really make a difference both for you as the service provider and as the customer receiving the care. When someone buys a product, it's partially about the cost and the feature set, but for your best customers, it's also about buying into the person on the other end of the transaction. Having the integrity to keep things "painted on the inside" really matters in the long run, because eventually it shows. You can't hide it. Eventually, it will get out and when it does, it will define for others who you are.

Most importantly, however, long before anyone else will know, you will. You can go on putting "lipstick on a pig" for a long time and be successful at it, but from the beginning you'll know and that will effect the way you treat the product and treat yourself. I'm not suggesting everything you do must be perfect, but it really needs to be your very best. You could be doing your very best and still be unsuccessful in a myriad of ways, but it's much easier to learn from your mistakes when you can look back and honestly say, "Well, I did the best I could." Additionally, there's something very peaceful and happy about doing great work, even if it's only great for you. The alternative is in my mind untenable because, "You know, when you start cutting corners, who knows where you'll stop?"

Unweary

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Starting today I'll be writing at a new blog location: http://unweary.com/blog/ I've redirected the old RSS feed http://feeds.feedburner.com/davidweiss to the new blog. If you want to subscribe to the shiny new RSS feed http://feeds.feedburner.com/unweary please go right ahead. At some point I'll take down the old RSS feed.

This change includes an upgrade from Blogger to Movable Type as my blogging platform, but if you sensed that there was more to the blog location change than just that, you were right. I'm "going indie", as they say. :-) This is something I've wanted to do for a long time and now is the time to make it official.

I quit working for the MacBU at Microsoft in December 2007 to go back to school. I'm very much enjoying school, and I'm trying hard to keep that my main focus, but I keep wanting to build stuff and publish it and Unweary is just a natural result of that innate desire to create. I expect to build pretty focused, humble, non-life changing software that just makes regular things easier and better in some way. Right now I'm mostly trying to decide which idea to tackle first. I feel like a kid in a candy shop!

So that's the news. I'm sure I'll write more about the adventure as it develops, but in the meantime, wish me luck!

Experience

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Especially with a code base that is mature, assumptions correctly made years ago can be terribly difficult to deal with later when the current and new assumptions reign. Writing code that lasts even 5 years and "is robust" is what everyone wants to do for sure, but the recipe for doing just that is not easy to learn and even harder to actually do. For example, you might know what changes need to be made to conform to even the most obvious object oriented design principles, but the business requirements and time to market needs dictate leaving once again old crusty code alone and racking up yet another round of technical debt. Over time, this technical debt will demand payment and the effects on your ability to hire, employee morale, design changes possible, speed of delivery, testing burden, marketing message etc. become very real and very painful. I wonder, can these concepts can be fully learned without actually experiencing pain? Could you even attempt to learn these concepts experientially in college? My experience so far makes me think that one may know something intellectually, without really knowing it. It seems like for so many, one may talk about design patterns or abstraction or low coupling, but until you actually try to build something the other way, the painful way, you just don't appreciate what you are avoiding. What's worse, junior developers who, for no fault of their own lack experience with "the hard way" have a difficult time understanding why one must "go the long way around" to do what seems like such a direct solution. Passing on the stories of the past and their consequences and lessons seems to be an unending challenge.

From my economics book comes this fictional story which I think illustrates the point:

"One Pepsi plant is managed by an economics major with an MBA and has a labor force with an average of 10 years of experience. This plant produces a larger output than does an otherwise identical plant that is managed by someone with no business training or experience and that has a young labor force that is new to bottling."

I definitely fall into the "young labor force that is new to bottling" camp. In the technology industry there is a tendency to glorify the young and bright rather than those who have the experience and have paid the price to learn the lessons that matter in the long run. Whenever I talk to some developer and we talk about where they learned some valuable lesson about software development, rarely do they refer to a book. Almost invariably, they say, "I worked with Joe on this project and he showed me x, y and z. I learned so much working with him." Smart developers, experienced developers who know how to teach and share important lessons to junior programmers seem like a key to the experience problem. Sadly, junior developers who have the presence of mind to ask, listen and apply what they hear are hard to find, and senior developers who are both willing and able to teach effectively are even more rare.

Perhaps the answer to all this is simple. Perhaps it's just he or she who writes the most code, wins. What I mean by this is simply when one writes a lot of code that increases the probability that he or she will make more of the key mistakes needed to learn how to write software with longevity. Just getting more exposure to "how bad things can get" helps bring a sober reality to each line of code written thereafter.

What's remarkable about all this, is that failures in teaching and learning are what keep us "discovering" new ideas that are 40 years old. Truly, "there is no new thing under the sun."

Don't Fight the Music

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As with most forms of art, there are those pieces of music or sculpture or painting that you'll dislike. Perhaps what they portray or teach don't match with your ideals of right and wrong. You'll disagree on a moral level. Perhaps they bring forth memories of the past. Maybe they just look or sound chaotic and simply don't make any sense to you. In all honesty you may not know why you don't like the art, but it might just be grating to you and make you want to turn away. Still, there was and often is a real, living, feeling, breathing human being full of senses, sympathies, misgivings, prejudice and paradoxes behind that creation. Behind all art, prose and poetry are the feelings approximated in the expressions of their craft. The ability to see and feel through the art into the heart of another person, this is the challenge and amazing quality of art. Everyone has a song and they are always singing it. They want to be heard, really listened to, and find out they are not alone.

Appreciating art because of the human behind it, has for me become a simile to working with people with whose opinions I disagree. My Dad would say, "Son, behavior has its reasons." I first remember him saying this when I worked as a Scout leader and got a front seat to the varied expressions of teenage boys. Invariably as I got to know each boy, I found many reasons for strongly held opinions, and behaviors. Often, the life experiences behind these behaviors even for young boys are deep and poignant.

I see similar issues when working in a team of people. The disagreements had in office discussions of the "obviously objective" technology problems often have their roots in other aspects of life much deeper and more powerful and often hidden. This is why teams that have learned to interact with each other "off the clock" as friends and treat each other as respected individuals, for who they are, today, are more successful at solving problems.

I like a good debate and enjoy the challenge of a difficult problem and opposing viewpoints. My experience at Microsoft was of a very "challenging" kind of culture. There you can't squeak out an idea without several counters and objections. This can be good, honest disagreement, but also can turn into ugly contention that yields no redeeming fruit. (It can also drown out innovation since ideas don't have time to germinate and grow and most importantly interact.) Everyone has different tolerance levels for this kind of discord and those who are naturally shy, not quick witted in a debate, or easily persuaded will often find themselves quieted and discontent. This is especially sad when that individual is full of really good ideas, ideas that need to be listened to and acted upon.

Certainly you can't change others, but how can you avoid the destructive discord? How do you know when a good debate has turned into a bad debate? I have noticed in myself the following warning signs:

Respect. If I don't have a deep respect, on a personal level, for the people with whom I'm working, a discussion can degrade incredibly fast. When I'm working with people like this, I have to keep on a higher state of alert.

Civility vs. Hostility. This includes the obvious things like pointing and repeating "you" a lot. In all things keep the discussion civil. Take the time to reinforce with sincerity that you think there's something you don't understand. Let them know you are pushing forward because you think there's something important worth understanding.

Desire to understand. When I sense my desire to understand dissipate and my desire to prove myself right increase, this is a sure indication that the discussion is heading down a destructive path. I can feel it. There's something not right in the air. I get tense, not relaxed. These are signs for me that I need to regroup, reevaluate and possibly try again later.

Judgement. Another indicator is if I am in my mind passing judgement on the individual. I can sense this when I find that I'm thinking about what I'm going to say next while they are still talking, or when I interrupt their thoughts and don't let them finish. I think I already know what they are going to say, so why wait it out? This kind of impetuous behavior indicates that I'm placing myself on a higher moral ground, and this lack of humility doesn't allow understanding, and without understanding, there's little possibility of unity or resolution.

I'm sure there are other even better ways to avoid the pointless and destructive arguments, but this is what I've found so far. In reality, everyone has a song. Listen to it. Find the art in it. Discover what it is saying and if possible the reasons behind the melody. Don't fight the music. There's a person in there waiting to be found.