The experience of signing in to your PC with touch has traditionally been a cumbersome one. In a world with increasingly strict password requirements—with numbers, symbols, and capitalization—it can take upwards of 30 seconds to enter a long, complex password on a touch keyboard. We have a strong belief that your experience with Windows 8 should be both fast and fluid, and that starts when you sign in.
Other touch experiences in the marketplace have tried to tackle this problem, with the canonical example being a numeric PIN. A PIN is a great solution: Almost everyone has seen or used one before, and a keypad is simple to use with touch. We knew though, that there was room to improve.
A numeric combination often presents a problem for people because the sequences easiest to remember are typically the least secure. Common number sequences—like 1111, or 1234—are troublesome, but PINs that are composed of common well-known personal dates can also be deduced if an attacker has personal knowledge of the person (much of which is not hard to obtain). In such a case, the number being personal to a person can work against its security. We set out to change the paradigm here: we designed a fast and fluid touch sign-in experience that is also personal to you.
Picture password is a new way to sign in to Windows 8 that is currently in the Developer Preview. Let’s go behind the scenes and see how secure this is and how it was built. One of the neat things about the availability of a touch screen is that it provides an opportunity to look at a new way to sign in to your PC. While many of us might prefer to remove the friction of getting to a PC by running without a password, for most of us, and in most situations this is not the case or is at least unwise. Providing a fast and fluid mechanism to sign in with touch is super important, and we all know that using alpha passwords on touch-screen phones is cumbersome. This post is authored by Zach Pace, a program manager on our You Centered Experience team, and looks at the implementation and security of picture password in Windows 8. Just as a note, you can also use a mouse with picture password too, just by using some click and/or drag actions.
At its core, the picture password feature is designed to highlight the parts of an image that are important to you, and it requires a set of gestures that allow you to accomplish this quickly and confidently. In order to determine the best set of gestures to use, we distributed a set of pictures to a set of study participants and asked them to highlight the parts of the image that were important to them. That’s it, no additional instructions. What we found were people doing three basic things: indicating location, connecting areas or highlighting paths, and enclosing areas. We mapped these ideas to tap, line, and circle, respectively. It’s the minimal set of gestures we found that allowed people to signify the parts of the image most important to them.
There’s also an attribute inherent to circle and line gestures that adds an additional layer of personalization and security: directionality. When you draw either a circle or a line on your selected picture, Windows remembers how you drew it. So, someone trying to reproduce your picture password needs to not only know the parts of the image you highlighted and the order you did it in, but also the direction and start and end points of the circles and lines that you drew.
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