What is the difference between ML-KEM and CRYSTALS-Kyber?

ML-KEM is the standardized post-quantum key encapsulation mechanism defined in NIST FIPS 203, based directly on the CRYSTALS-Kyber algorithm.

Which ML-KEM parameter set is recommended for general use?

ML-KEM-768 is the recommended default, providing a balance of high security (NIST Security Category 3) and efficient key and ciphertext sizes.

What are the exact wire sizes for ML-KEM-768?

ML-KEM-768 uses an encapsulation key of 1,184 bytes, a decapsulation key of 2,400 bytes, a ciphertext of 1,088 bytes, and a shared secret of 32 bytes.

How does deterministic mode work?

Providing a valid hex seed forces the internal random number generator to derive keypairs and encapsulation randomness deterministically, ensuring reproducible outputs.

Why is the decapsulation key hidden by default?

The decapsulation key is sensitive private key material, so it is masked by default and only displayed when the reveal option is checked.

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ML-KEM / Kyber Keypair & Encapsulation Tester

Generate ML-KEM-512/768/1024 (FIPS 203 / CRYSTALS-Kyber) keypairs, encapsulate a random shared secret against the public key, decapsulate it with the private key, and verify both sides match — with the exact wire sizes of all three parameter sets checked live against the standard.

Execution

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2 examples

Deterministic ML-KEM-768 round trip

A fixed hex seed makes the whole exchange reproducible: keygen, encapsulation and decapsulation all derive from it, so the ciphertext and shared secret are byte-stable — handy for cross-library interop tests against your own FIPS 203 implementation.

<section class="mk-wrap">ML-KEM-768 card: keygen → ek 1184 B · dk 2400 B, encapsulate → ct 1088 B · ss 32 B, decapsulate recovers the identical shared secret (✓ verdict), hex key material, FIPS 203 table with all three sets matching</section>

All three parameter sets side by side

Runs 512, 768 and 1024 together: every set does its own keygen/encapsulate/decapsulate round trip and the report shows the exact wire sizes — 800/1632/768, 1184/2400/1088 and 1568/3168/1568 bytes — the numbers that decide packet and header budgets.

<section class="mk-wrap">three ML-KEM cards (512 / 768 / 1024), each with its ✓ round-trip verdict and hex material, plus the FIPS 203 parameter table with live size checks</section>

Inputs

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4 options

ContentPaste or type the main input values.1

Deterministic seed (hex, optional)textOptional

SettingsAdjust formats, ranges, numbers, and modes.2

Parameter setselectRequiredOutput formatselectRequired

TogglesEnable or disable optional behavior.1

Reveal decapsulation keycheckboxOptionalEnabled when checked

Result

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Samples

ML-KEM / Kyber Keypair & Encapsulation Tester

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Key facts

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Examples

1. Deterministic ML-KEM-768 Round Trip

2. Wire Size Comparison Across All Parameter Sets

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