Cellframe Alphabet: Asymmetric Encryption

Asymmetric encryption is a method of securing data that uses two different keys: a public key (for encrypting data and verifying signatures) and a private key (for decrypting data and creating signatures). When a user wants to send tokens, they sign the transaction with their private key, creating a digital signature. The network then verifies this signature using the public key, ensuring that the transaction was indeed initiated by the rightful owner.

Among the classical algorithms, asymmetric ones include, for example, the ECDSA digital signature algorithm and also RSA-2048. They are used by many popular blockchain platforms.

The foundation of these algorithms lies in distinct mathematical problems: elliptic curves for ECDSA, and integer factorization (breaking down large numbers into prime factors) for RSA-2048. While the problems are very different, they share a critical vulnerability: both can be solved efficiently by a quantum computer using Shor’s algorithm.

Post-quantum signatures are also asymmetric, but they are based on mathematical problems that are believed to be resistant to Shor’s algorithm. These include lattices, hash functions, multivariate quadratic equations, isogenies, and error-correcting code problems.

Within the Cellframe blockchain, signatures from two of these families have already been integrated: Falcon and CRYSTALS-Dilithium (lattice-based), as well as SPHINCS+ (hash-based). The latter, however, has a very large signature size, so we recommend using it only in exceptional cases — though it is available in our SDK if needed.

We built support for post-quantum cryptography into Cellframe from the very beginning of the design stage. To achieve this, we developed mechanisms that allow the blockchain to operate efficiently even with heavy post-quantum signatures. More importantly, we also implemented mechanisms for quickly removing or adding new algorithms. This means the list of supported schemes is not final — it will evolve as post-quantum cryptography advances and as new standards are established by NIST. Most importantly, if one of our supported algorithms is ever broken in the quantum era, we will be able to rapidly replace it with a stronger and more efficient one.