Dilithium2

Dilithium2 is a parameter set of the CRYSTALS-Dilithium digital signature scheme, a lattice-based post-quantum cryptographic primitive designed for secure digital signatures in environments where quantum attacks are a concern. It is one of the three primary parameter sets in the Dilithium family, alongside Dilithium3 and Dilithium5, and corresponds to a particular security/performance profile used in practical deployments.

The scheme relies on module-LWE and module-SIS problems over a polynomial ring and operates with polynomials of a fixed degree. Keys are generated by sampling secret polynomials from small distributions and forming a public key as a short vector of polynomials, with the secret key comprising the private polynomials. Signing a message involves producing a short signature vector and computing a challenge from the message via a hash function; verification checks the consistency of the derived values with the public key and the hash, without revealing the secret key.

In terms of security and performance, Dilithium2 is designed to provide a balanced level of post-quantum security, often associated with about 128-bit security in the standardized framework, while offering relatively efficient signing and verification compared with higher-security variants. The Dilithium family allows higher security levels with Dilithium3 and Dilithium5, which typically incur larger key and signature sizes and longer signing times.

Dilithium2 has been part of the public discussion around post-quantum standards and is used in cryptographic libraries and protocols that implement lattice-based digital signatures for environments requiring resistance to quantum adversaries.