POSERS: A Steganography-Driven Molecular Tagging System Using Randomized DNA Sequences for Secure Authentication.

Counterfeiting remains a major threat across multiple industries, causing substantial financial losses and health-related risks. DNA-based molecular tagging has emerged as a promising anticounterfeiting strategy, but existing methods rely on predefined DNA sequences, making them increasingly vulnerable to replication as sequencing and synthesis technologies advance. To address these limitations, we introduce POSERS (Position-Oriented Scattering of Elements among a Randomized Sequence), a steganographic DNA tagging system that encodes product-specific constraints into highly diverse, randomized DNA libraries. While the underlying design is adaptable to other molecular or material carriers, DNA offers a particularly attractive option due to its chemical stability, low synthesis cost, and proven compatibility with materials such as inks, polymers, and coatings. Unlike previous methods that use fixed tags, POSERS enables customizable design complexity and offers resilience against replication attempts. Each product in a batch receives a unique DNA library generated in a single synthesis step, allowing for cost-effective, large-scale deployment. The security of POSERS is mathematically validated and experimentally confirmed using next-generation sequencing, combined with complementary authentication tests that detect both unauthorized sequence combinations and insufficient diversity. POSERS consistently distinguishes genuine tags from forgeries, even under conservative assumptions about an attacker's knowledge and capabilities. Our approach prevents both PCR-based copying and reverse-engineering of tag designs. With its customizable design parameters, minimal DNA input requirements, and demonstrated robustness against current and emerging attacks, POSERS establishes a new standard for secure molecular tagging and offers a scalable, future-proof solution for high-risk products.