An Adaptive Quantization Algorithm for Secret Key Generation Using Radio Channel Measurements

Abstract

Abstract-New approaches that generate secret keys from radio channel characteristics have been recently proposed. The security of these schemes usually relies on the reciprocity principle which states that the channel fluctuations can be a source of common randomness for two communicating peers and these fluctuations can't be measured by any eavesdropper. A validation of these properties for indoor environments is presented in this work. The shared keys are created by measuring the reciprocal channel features and converting this information to binary vectors using a quantization algorithm. This paper addresses the problem of quantization. It identifies an important weakness of existing key generation algorithms and it shows that the secret bits extraction has a significant impact on the robustness and security of these algorithms. A new adaptive quantization algorithm for secret key generation is presented. This method has the advantages to create sufficient long secret keys with a high key agreement ratio between authorized users without revealing information to the attacker. The new scheme is experimentally validated using Ultra Wide Band technology.

The Channel Quantization Alternating Algorithm in the Secret Key Generation System

“…In [1], Sana Hamida et al proposed an adaptive quantization algorithm, which adjusts the quantization threshold adaptively to reduce the bit error rate; In [2][3], a two-threshold quantization algorithm is adopted, the algorithm quantizes the value larger than the upper threshold to '1', smaller than the quantization of the lower threshold to '0', and discards the sampling value between the upper and lower thresholds, the uncertainty of quantization interval of sampled value is reduced, but the quantization factor of the algorithm is a fixed value, and there is no specific analysis of the value of the quantization factor to the key generation process; In [4], Wenbing Cai et al taked the key length as the objective function, computed the optimal quantization factor when using the two-threshold quantization to generate the longer key, so that the key length of each sample value increased at least 0.1 bits, but the algorithm quantization deleted a lot of the original information, in essence, or shorten the length of the generated key. In [5], Chan Chen et al proposed a CQA (Channel Quantization Alternating) quantization algorithm, which achieves reducing the error rate by exchanging the quantization error information and moving the quantization threshold of the other communication side; Reference [6] based on [5] taked the key length as the objective function to compute optimal number of quantization bits for the longest key length.…”

Public discussion strategies for secret key generation from sampled IR-UWB channel responses

“…Despite their diversity, they all imply the existence of either an initial secure channel for symmetric cryptography or a certification infrastructure for public key cryptography. An alternative paradigm to these key management techniques stems from earlier informationtheoretic work on secret sharing based on a source model or a channel model [4] 1 . Given a common source of randomness and a previously authenticated public channel with no prior secret key, two parties can securely generate a common secret key using a sequential key distillation procedure [5].…”

“…Physical layer key generation exploits the radio channel as a common source of information for a pair of transceivers 1 Only the source model will be considered for further discussions. which probe the channel and quantize their observations (e.g.…”

“…which probe the channel and quantize their observations (e.g. received power [6], channel response [7], [8], [1] etc.) to obtain bits.…”

Threat on Physical Layer Security: Side Channel vs. Wiretap Channel

“…In the second phase, the obtained channel characteristics are quantized and converted to a binary vector. In the third phase, Alice and Bob agree on the secret key [11].…”