Signcryption integrates a digital signature with public-key encryption to provide confidentiality and authenticity simultaneously, which is crucial in many applications. Nowadays, most existing signcryption schemes are classical and thus vulnerable to Shor’s algorithm on future advanced quantum computers, so quantum-resistant signcryption is an important research direction. Although several post-quantum signcryption designs have been proposed, some exhibit security shortcomings or lack practical instantiations and empirical evaluation. To address this gap, this study proposes DILISAES, a lattice-based experimental signcryption scheme with security proofs achieving IND-iCCA confidentiality and SUF-iCMA unforgeability. Among insider-secure lattice signcryption schemes, DILISAES attains smaller public keys, secret keys, and ciphertexts. In performance, DILISAES delivers lower end-to-end latency than most baselines that apply post-quantum encryption and signatures separately at matched security levels. These results indicate that DILISAES offers a practical path toward efficient, quantum-resistant signcryption.