About crypto-sizes.tools

crypto-sizes.tools is a reference for the practical cost of moving to post-quantum cryptography. The algorithms NIST standardised in 2024 work, but their keys, ciphertexts and signatures are many times larger than the RSA and elliptic-curve values they replace, and that size is what breaks handshakes, certificates and constrained devices first. The comparator puts every figure in bytes next to a classical baseline you choose.

What is on the site

• Size comparator: ML-KEM, ML-DSA, SLH-DSA and FN-DSA (Falcon) against RSA and elliptic curve, from FIPS 203, 204 and 205 and the FN-DSA draft.
• Deprecation timeline: algorithm status under NIST SP 800-131A and related guidance, with the dates that actually apply.
• PQC migration lookup: which post-quantum algorithm replaces which classical function, and by when, across the major frameworks.

Every figure is taken from the primary standard rather than from secondary sites, many of which still quote draft parameters or superseded dates. The size data is also published as a downloadable data file for anyone who wants to reuse it.

Who makes it

crypto-sizes.tools is one of a small family of free security reference tools (the others are linked in the footer and collected at sec-ref.tools). They are built and maintained by a working security researcher who uses them day to day, because the generic calculators for these tasks are often out of date, cluttered, or wrong, and a good reference tool should not require an account.

Accuracy

Care is taken to keep the reference data correct, but these tools are provided for general information and estimation. For anything that matters, verify against the primary standard or data source, each of which is linked from the relevant tool. See the Terms for the full disclaimer.

Contact

Corrections, bug reports and suggestions are welcome. Email contact@sec-ref.tools, or see the contact page.