Symmetric-key cryptography can resist the potential post-quantum attacks expected with the not-so-faraway advent of quantum computing power. Hash-based, code-based, lattice-based, and multivariate-quadratic equations are all other potential candidates, the merit of which is that they are believed to resist both classical and quantum computers, and applying “Shor’s algorithm”—the quantum-computer discrete-logarithm algorithm that breaks classical schemes—to them is infeasible. In this article, we propose, assess, and benchmark reliable constructions for stateless hash-based signatures. Such architectures are believed to be one of the prominent post-quantum schemes, offering security proofs relative to plausible properties of the hash function; however, it is well known that their confidentiality does not guarantee reliable architectures in the presence natural and malicious faults. We propose and benchmark fault diagnosis methods for this post-quantum cryptography variant through case studies for hash functions and present the simulations and implementations results (through application-specific integrated circuit evaluations) to show the applicability of the presented schemes. The proposed approaches make such hash-based constructions more reliable against natural faults and help protecting them against malicious faults and can be tailored based on the resources available and for different reliability objectives.