What are FIPS 203, 204 and 205?
They are the first three post-quantum standards from the US National Institute of Standards and Technology (NIST), published on 13 August 2024 after an open, international competition that began in 2016. FIPS 203 specifies ML-KEM, a key-encapsulation mechanism that lets two parties agree on a shared secret key; it takes over the role RSA and elliptic-curve Diffie-Hellman play in key exchange today. FIPS 204 specifies ML-DSA, the main digital signature scheme. FIPS 205 specifies SLH-DSA, a slower signature scheme with larger signatures that relies only on hash functions, kept as a conservative alternative. Although they are US federal standards, they are the reference worldwide: European agencies such as Germany's BSI and France's ANSSI recommend these algorithms, among others, usually combined with a classical one. For you, they are the names to look for in vendor documentation, product roadmaps and tender answers.
This answer is part of the guide: Post-quantum readiness: where to start