Abstract. The development of quantum computing poses a threat to classical cryptographic schemes of electronic signature (RSA, ECDSA), the security of which is based on the computational complexity of factorization and discrete logarithm. Post-quantum algorithms (Dilithium, Falcon, SPHINCS+) solve the problem of protection against quantum attacks but do not provide authentication of a specific person as the author of the signature. The paper proposes a multilevel architecture of post-quantum data protection that combines biometric authentication of a handwritten digital signature, post-quantum cryptography, steganographic information protection, and Explainable AI (XAI) technologies. The architecture includes five interrelated levels of protection: biometric identification; post-quantum cryptography with a key generated “on the fly”; steganographic concealment of cryptographic parameters; analysis of anomalous activity (liveness detection); and regulatory support. It is shown that the probability of a successful complex attack is determined by the product of conditional probabilities of compromising individual levels, which significantly reduces the risk compared with single-level schemes. The practical feasibility of the approach is confirmed by an operational prototype of a multilevel encoding service.