CPU is a major source of power consumption in smartphones. Power modeling is a key technology to understand CPU power consumption and also an important tool for power management on smartphones. However, we have found that existing CPU power models on smartphones are ill-suited for modern multicore CPUs: they can give high estimation errors (up to 34%) and high estimation accuracy variation (mor...

Completely Automated Public Turing tests to tell Computers and Humans Apart (captchas) are challenge-response tests used as a security mechanism on the web to distinguish human users from automated programs. While captchas are often necessary to stop abuse of resources, most existing schemes are intended for traditional desktop computing environments rather than for mobile device usage. In this...

Smartphone technology is more and more becoming the predominant communication tool for people across the world. People use their smartphones to keep their contact data, to browse the internet, to exchange messages, to keep notes, carry their personal files and documents, etc. Users while browsing are also capable of shopping online, thus provoking a need to type their credit card numbers and se...

By 2025, when most of today’s psychology undergraduates will be in their mid-30s, more than 5 billion people on our planet will be using ultra-broadband, sensor-rich smartphones far beyond the abilities of today’s iPhones, Androids, and Blackberries. Although smartphones were not designed for psychological research, they can collect vast amounts of ecologically valid data, easily and quickly, f...

As smartphones are generalized, various technologies and services have been introduced and are in wide use. From simply using calling or texting services, Internet banking and transaction system that require sensitive personal information emerged. Google’s Android, one of the representative OS of smartphones, was developed based on an open source, having various weaknesses and exposed to securi...