A Secure Turbo Codes Design on Physical Layer Security Based on Interleaving and Puncturing

Nowadays, improving the reliability and security of the transmitted data has gained more attention with the increase in emerging power-limited and lightweight communication devices. Also, the transmission needs to meet specific latency requirements. Combining data encryption and encoding in one physical layer block has been exploited to study the effect on security and latency over traditional sequential data transmission. Some of the current works target secure error-correcting codes that may be candidates for post-quantum computing. However, modifying the popularly used channel coding techniques to guarantee secrecy and maintain the same error performance and complexity at the decoder is challenging since the structure of the channel coding blocks is altered which results in less optimal decoding performance. Also, the redundancy nature of the error-correcting codes complicates the encryption method. In this paper, we briefly review the proposed security schemes on Turbo codes. Then, we propose a secure turbo code design and compare it with the relevant security schemes in the literature. We show that the proposed method is more secure without adding complexity.

I. Introduction

The reliability and security of data transmission through wireless are essential to meet the demand for an increase in emerging wireless networks. Error-correcting codes have been advanced to deliver reliable transmission over unreliable channels in the last decades. Shannon stated that through channel coding, an arbitrarily small probability of error could be achieved at the receiver when the information rate does not exceed the channel capacity [1]. In modern communication systems, robust channel coding standards have been adopted (e.g., Turbo Codes (TC) in 3G/4G and Low-Density Parity Check (LDPC) codes in 5G data channels [2]). Turbo code’s capability to achieve the Shannon limit’s maximum rate made it more desirable for noisy communication link applications. On the other hand, symmetric encryption like the Advanced Encryption Standard (AES) has replaced the Data Encryption Standard (DES) and is still secure against the most reduced complexity attacks. In the conventional system, encryption is performed before error-correcting codes to guarantee the data’s confidentiality. Though this approach is considered safe, there are some drawbacks when implemented in lightweight devices such as the Internet of Things (IoT) and Cyber-Physical System (CPS). The computational complexity and latency are two main issues that need to be considered. Therefore, new research focuses on combining encryption and channel coding, referred to as Secure error-correcting codes (SEC), to minimize the complexity constraints. Robert McEliece [3] proposed error-correcting codes as a cryptosystem with the use of binary irreducible Goppa codes. The security of the algorithms relies on the fact that extracting the generating matrix from the public key is infeasible for long codeword length and arbitrary error vector, and the scrambling process by non-singular matrix and permutation matrix makes it more challenging. Moreover, decoding the ciphertext without knowing the generating matrix is NP-complete. However, the large matrices used as public and private keys are the major drawbacks in the McEliece cryptosystem compared to other public cryptography like a modified private-key algebraic-coded cryptosystems was proposed in [4] that use modified McEliece codes with simpler channel coding. The current cryptosystem depends on factoring large numbers and solving discrete logarithms, which might not resist the breaking in polynomial time [5] when the era of quantum computing starts. On the contrary, error-correcting codes-based cryptosystem like McEliece seems robust against known attacks and is considered a candidate for post-quantum computing [6]. Physical Layer Security (PLS) such as SEC relies on information-theoretic metrics to replace or complement conventional high layers of security standards. Survey for PLS techniques can be found in [7] [8]. In this paper, we review the SEC techniques published on the turbo codes security approaches and demonstrate the security and complexity of the proposed approaches. Then we present the proposed secure turbo codes to eliminate the drawbacks of the previously published works.