RCSChain is an open-source, multi-node blockchain-based file storage system designed to deliver unparalleled security and resilience. RCSChain leverages the power of post-quantum cryptography and decentralized architecture to create a tamper-proof, future-ready platform for storing and managing files. Unlike traditional storage solutions that rely on centralized servers or pre-quantum encryption vulnerable to emerging quantum computing threats, RCSChain uses the Falcon-512 signature scheme—a cutting-edge, quantum-resistant algorithm—to secure every transaction and ensure data integrity across its distributed network.
At the heart of RCSChain lies Falcon-512 (https://falcon-sign.info), a cutting-edge post-quantum cryptographic signature scheme that ensures the system’s security remains unbreakable even in the face of quantum computing advancements. Developed as part of the NIST Post-Quantum Cryptography Standardization Project, Falcon (Fast Fourier Lattice-based Compact Signatures over NTRU) is a lattice-based algorithm designed to withstand attacks from both classical and quantum computers. Unlike traditional cryptographic systems like RSA or ECDSA, which rely on mathematical problems (e.g., integer factorization or discrete logarithms) that quantum algorithms like Shor’s could solve in seconds, Falcon-512’s security is rooted in the hardness of lattice problems—specifically, the Short Integer Solution (SIS) and Learning With Errors (LWE) problems. These are widely believed to be resistant to quantum attacks, making Falcon-512 a cornerstone of RCSChain’s quantum-safe design.
In RCSChain, Falcon-512 serves dual purposes: securing the blockchain ledger and authenticating peer-to-peer communication. Every block—whether it’s an uploaded file, a folder creation, or a deletion—is signed with a Falcon-512 signature (~666 bytes, compressed to ~400-500 bytes with zlib), linking it immutably to the previous block via a hash. This ensures that any attempt to tamper with the data would invalidate the signature, alerting the network to the breach. Similarly, nodes use Falcon-512 to sign messages exchanged over the encrypted Kademlia DHT, verifying their identity and preventing unauthorized access. The choice of Falcon-512 over other post-quantum candidates (like Dilithium or SPHINCS+) reflects a balance of security (~128-bit quantum security), efficiency, and compact signature sizes, optimized further with compression to keep network overhead low.
Falcon Performance Example:
While resistance to quantum computers is the main drive for the design and development of Falcon, the algorithm may achieve significant adoption only if it is also reasonably efficient in our current world, where quantum computers do not really exist. Using the reference implementation on a common desktop computer (Intel® Core® i5-8259U at 2.3 GHz, TurboBoost disabled), Falcon achieves the following performance:
| Variant | Keygen (ms) | Keygen (RAM) | Sign/s | Verify/s | Pub Size | Sig Size |
| Falcon-512 | 8.64 | 14366 | 5948.1 | 27933.0 | 897 | 666 |
| Falcon-1024 | 27.45 | 28672 | 2913.0 | 13650.0 | 1793 | 1280 |
RCSChain opted for Falcon-512 over Falcon-1024 to strike an optimal balance between network performance and robust security, tailored to the demands of a distributed file storage system. Falcon-512 generates signatures around 666 bytes (compressed to ~400-500 bytes with zlib), significantly smaller than Falcon-1024’s ~1330 bytes, reducing network overhead and speeding up synchronization across nodes—critical for a scalable, multi-node setup. While Falcon-1024 offers a higher security level (~256-bit quantum security) with its larger signatures, Falcon-512’s ~128-bit quantum security is widely considered sufficient to thwart most quantum attacks, including those leveraging algorithms like Grover’s, making it a practical choice without sacrificing future-proofing. This trade-off ensures RCSChain delivers fast, efficient performance while remaining a fortress against both classical and quantum threats.
Why does this matter? As quantum computing inches closer to reality, traditional encryption schemes face an existential threat, potentially exposing vast swaths of stored data to decryption. RCSChain, by integrating Falcon-512, leapfrogs this risk, offering a file storage system that’s ready for the quantum era today. It’s not just theoretical—Falcon-512 is part of the PQClean library, rigorously vetted and implemented in RCSChain via a shared library (libfalcon.so), ensuring production-ready reliability. For contributors and users alike, this means RCSChain isn’t just keeping pace with security trends; it’s setting the standard for how post-quantum cryptography can be practically applied to decentralized storage. Want to dig deeper into Falcon’s math or implementation? Check out the PQClean repo or join RCSChain on GitHub to explore how we’ve harnessed post-quantum cryptography!