PQCrypt

Quantum-safecryptography, learned in the open.

A free course, interactive tools and a news desk for the move to post-quantum cryptography.

Start learning Open the tools

Background: a 2D lattice and its closest-vector search, the geometry behind ML-KEM.

The standards are final. What is left is the migration, and the migration needs people who understand it.

NIST published FIPS 203, 204 and 205 in August 2024. Since then the work has moved to engineers, architects and auditors who have to change real systems. PQCrypt is our contribution to that ecosystem: everything we learn, written down, sourced, and free to use.

What we build

DocsA 16-module course from the quantum threat to scoping a bank migration. Three levels on one spine: foundations, practitioner, advisor.ToolsCalculators you can defend on a whiteboard: TLS handshake bytes, algorithm sizes, Mosca's inequality, cost ranges, a regulatory timeline and a decision tree.PracticeCheckpoint questions with model answers and rubrics, spaced-repetition flashcards, and an objection drill for meetings with CISOs and auditors.NewsA short, curated desk of what moved in standards, policy and industry, each item linked to its primary source and to the lesson that explains it.SourcesEvery primary document the course cites, with priority, citing lessons and a visible flag when a source has a commercial stake.

Every number shows its receipts.

All 152 numbers in the course live in one keyed file. Each carries a tag: measured by a command we ran, sourced from a primary document, derived with the arithmetic shown, or estimated with assumptions listed. Hover any badge to see where it came from.

When we find an error, the old value stays visible. Our early research notes claimed a 12.5 KB post-quantum certificate chain. Measuring it gave a different answer.

ML-KEM-768 public keyFIPS 203, Table 3
1184 BSOURCED
Hybrid ClientHelloopenssl s_client
1484 BMEASURED
ML-DSA-65 chain vs RSA-2048 chain22,945 / 3,739
6.14×DERIVED
DER overhead per certificateassumptions listed
393 BESTIMATED

Correction on record

12.5 KB13.8 KB22,945 BMEASURED

Three-certificate ML-DSA-65 chain, PEM, measured. The 13.8 KB figure turned out to include an RSA leaf.

Tools that show the arithmetic.

Flagship tool

TLS handshake byte calculator

Pick a key exchange, signature algorithm and chain shape. Get per-message bytes, segment count, the initcwnd warning and added latency, with every step shown.

Open calculator

Signature sizes

RSA-2048256 B
ML-DSA-442,420 B
ML-DSA-653,309 B
SLH-DSA-128s7,856 B

Mosca calculator

x + y > z

Shelf life plus migration time against the quantum timeline, with presets for bank data classes.

Regulatory timeline

Dated, sourced deadlines by jurisdiction, with a countdown to the next binding one.

Algorithm decision tree

From use case to recommendation, with the reasoning path and caveats visible.

What moved this month

All news

How a lesson ships

PQCrypt is built with Claude Code. Lessons are written and checked through four agent roles, each with its own brief and its own rules.

  1. Research

    Find two to four primary sources for the topic. Standards, papers and regulator texts first.

  2. Verify

    Re-check every number and status claim against its source, with a verification date.

  3. Run

    Execute each lab and record the real output. A lab is never written to confirm a target number.

  4. Challenge

    A hostile review as a bank crypto architect and as a lost beginner. Findings are fixed or answered.

Start at module zero.

Set up OpenSSL 3.5 or newer, confirm ML-KEM and ML-DSA work on your machine, and work forward from there.

Start learning