ShakeMe: Key Generation From Shared Motion

TL;DR

This paper proposes a method for generating shared cryptographic keys from shared motion, specifically shaking, using accelerometer data, achieving a balance of simplicity, speed, and reasonable security.

Contribution

It introduces a new feature selection approach that simplifies key quantization from shared motion data, improving efficiency over previous methods.

Findings

Achieved 76% accuracy in key agreement

Generated keys with approximately 15 bits of entropy

Demonstrated feasibility with authentic accelerometer data

Abstract

Devices equipped with accelerometer sensors such as today's mobile devices can make use of motion to exchange information. A typical example for shared motion is shaking of two devices which are held together in one hand. Deriving a shared secret (key) from shared motion, e.g. for device pairing, is an obvious application for this. Only the keys need to be exchanged between the peers and neither the motion data nor the features extracted from it. This makes the pairing fast and easy. For this, each device generates an information signal (key) independently of each other and, in order to pair, they should be identical. The key is essentially derived by quantizing certain well discriminative features extracted from the accelerometer data after an implicit synchronization. In this paper, we aim at finding a small set of effective features which enable a significantly simpler quantization procedure than the prior art. Our tentative results with authentic accelerometer data show that this is possible with a competent accuracy ($76$%) and key strength (entropy approximately $15$ bits).