A novel distortion-tolerant speech encryption scheme for secure voice communication

Description

This paper details a novel distortion-tolerant speech encryption scheme for securing voice communications over digital voice-specific channels such as 3G/4G or VoIP voice calls. The scheme relies on the usual "loudness, pitch and timbre" parametric representation of speech signals but seen as points on various perceptually-continuous manifolds linked by quasi-isometric continuous mappings. The ciphering of the vocal parameters of the initial speech is done by provably-secure, pseudo-random continuous transforms on these manifolds and hence ensures resilience against moderate errors. The enciphered parameters are then re-encoded into a pseudo-speech signal and transmitted over lossy digital voice channels with compression. Upon reception of the distorted pseudo-speech signal, the legitimate receiver retrieves corrupted versions of the initial vocal parameters and reconstructs an intelligible speech signal, perceptually close to the original, using a machine-learning vocoder derived from the LPCNet.The important parts of our scheme are extensively tested through simulations and experiments with encrypted pseudo-speech signals between different mobile phones. Furthermore, we detail a thorough speech quality subjective assessment with a group of 44 participants that demonstrates how the proposed scheme maintains intelligibility with tolerable progressive quality degradation linked to channel distortion. Finally, a preliminary computational analysis is done to justify the feasibility of real-time implementation of our scheme on portable devices.

Abstract

Received 24 March 2021; Received in revised form 5 June 2022; Accepted 23 June 2022; Available online 8 July 2022

Abstract

International audience

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