An encrypted and signed plaintext symmetric cryptosystem

Traditionally, encryption and digital signatures are handled as separate processes, resulting in distinct ciphertexts. This article investigates a novel approach to integrating encryption and digital signatures within a symmetric cryptosystem to meet the dual requirements of confidentiality, integrity, and authenticity in secure communications. Our research proposes a method that combines encryption and signature functionality within a probabilistic symmetric cryptosystem, reducing operational complexity and minimizing overhead. We introduce a protocol that employs a shared secret key for both encrypting plaintext and generating a verifiable signature within a single ciphertext. By modifying the encryption process, we enable certain variables to function as an implicit signature. The security and performance implications of this protocol are rigorously evaluated through theoretical analysis and experimental testing. Results show that the proposed scheme maintains robust security while significantly improving message-handling efficiency, it achieves four layers of security against quantum computer attacks and five against classical computers, compared to only one, two, or three layers in previous techniques in literature. To the best of our knowledge, this is the first protocol to merge encryption and digital signature creation into a single process and ciphertext, offering an enhanced solution for secure communications.