Comparison-Based Key Exchange and the Security of the Numeric Comparison Mode in Bluetooth v2.1

In this paper the authors study key exchange protocols in a model where the key exchange takes place between devices with limited displays that can be compared by a human user. If the devices display the same value then the human user is convinced that the key exchange terminated successfully and securely, and if they do not then the user knows that it came under attack. The main result of this paper is a rigorous proof that the numeric comparison mode for device pairing in Bluetooth version 2.1 is secure, under appropriate assumptions regarding the cryptographic functions used.