Post-quantum
encrypted messaging
over any channel
Encrypt a message or file with ML-KEM + AES-256-GCM directly in your browser, get a shortlink, and paste it wherever the conversation already is — work email, Slack, WhatsApp, SMS. No app to install, no platform both sides have to join, no plaintext on the server. Free.
Harvest now, decrypt later
The reason to encrypt a message post-quantum today, rather than when quantum computers arrive.
A quantum computer able to break RSA and elliptic-curve cryptography does not exist yet, and that is usually read as permission to wait. It is not, because the attack on a message does not have to happen while the message is in transit.
An adversary records your encrypted traffic today and does nothing with it. Ciphertext is cheap to archive. When a cryptographically relevant quantum computer arrives, the archive is decrypted retroactively. This is harvest now, decrypt later, and it is the specific threat that pushed Signal, Apple, Tuta and Proton to migrate years ahead of the machine itself.
For messaging the exposure is sharper than for stored files, because you do not control the channel. An email crosses several relays and sits in backups you will never see; a chat message lives on a platform whose retention policy can change. Encrypting the payload before it enters the channel is the only part of that chain you actually control — and if the payload is protected with ML-KEM, an archived copy stays unreadable no matter who kept it or for how long.
The same reasoning runs through the rest of PQCServer: permanent encrypted storage for files that must outlive the channel, notarisation and timestamping for proving a document existed at a point in time.
Three steps. No installation.
Everything happens in your browser. The server only stores encrypted data it cannot read.
Everything you need
Burn After Read
Enable burn-after-read to have the message permanently deleted from our server the moment the recipient opens it. Combined with TTL, messages never linger.
Attachments That Expire
Attach files of any size — chunked upload means no per-request size ceiling. Unlike the encrypted vault, message attachments are transient: they follow the message TTL and disappear with it. Send now, gone later.
Public Profiles
Register a username and share pqcserver.com/u/yourname. Anyone can send you an encrypted message without knowing your key in advance — just your username.
Embeddable Widget
Add a "Send encrypted" button to any website with one line of HTML. The modal opens inline — users never leave your site. Supports username lookup, manual key paste, or no configuration.
One line. Any website.
Put post-quantum encryption on your own contact form, intake flow or support desk — no backend work.
Known recipient:
data-recipient="alice_smith"></script>
Widget auto-loads Alice's public key and opens at Step 2 (message).
Unknown recipient — user picks:
Step 1 shows username lookup + manual key paste. Perfect for email clients.
The modal guides users through 3 steps:
The post-quantum messaging landscape
Who else has migrated, what they migrated, and where PQCServer sits differently.
PQCServer is not the only post-quantum option for private communication, and it would be dishonest to imply otherwise. Several major providers have already migrated, most of them using a hybrid construction that combines a classical key exchange with a post-quantum KEM, so that breaking either component alone is not enough to recover the message.
| Product | Post-quantum key exchange | Since | Scope |
|---|---|---|---|
| Signal | PQXDH, then SPQR (Triple Ratchet) — ML-KEM hybrid with X25519 | 2023 / 2025 | Signal-to-Signal only |
| Apple iMessage | PQ3 — post-quantum hybrid | 2024 | Apple devices only |
| Tuta Mail | TutaCrypt — Kyber hybrid with X25519 | 2024 | Tuta accounts |
| Proton Mail | OpenPGP v6 post-quantum keys, opt-in | 2026 | Proton accounts |
| Classic PGP / GnuPG | ✗ RSA / ECC — breakable by Shor's algorithm | — | Anywhere, with tooling |
| PQCServer | ML-KEM (FIPS-203) + AES-256-GCM, in-browser | — | ✓ Any channel, no shared platform |
Where PQCServer is different
Look down the Scope column and the pattern is clear: every one of those products protects you only when both sides are already inside the same platform. Signal protects Signal conversations. iMessage protects blue bubbles. Tuta and Proton protect mail between their own accounts, or fall back to a password exchange with everyone else. That is a reasonable design — it is also the reason most people's sensitive messages still travel unprotected, because the counterparty is on a corporate Outlook, a client's WhatsApp, or a supplier's Slack, and will not migrate.
PQCServer inverts it. Encryption happens in your browser and the output is a link. The link goes through whatever channel the conversation is already on, and the recipient opens it in a browser they already have. No install on either side, no account required to send, and no platform both parties have to agree to join. It is a layer over the channels you use, not another channel to talk your contacts into.
The second difference is that it is embeddable. One line of HTML puts a "send encrypted" button on your own site or web application, which none of the products above offer. If you run a contact form, a whistleblowing page, a client intake flow or a support desk, you can give post-quantum encryption to people who have never heard of PQCServer.
The trade-off is honest too: Signal's Triple Ratchet gives forward secrecy and post-compromise security across a long-lived conversation, which a link-based one-shot message does not attempt. For a continuing private conversation between two people who will both install an app, Signal is the better tool. PQCServer is for the message you need to send now, to someone who is not on your platform, through a channel you do not control.
Frequently asked questions
Post-quantum messaging and email, in plain terms.
What is post-quantum encrypted messaging?
It is messaging whose key exchange uses an algorithm that a quantum computer cannot break. PQCServer uses ML-KEM, standardised by NIST as FIPS-203, to derive the key that protects each message, instead of the RSA or elliptic-curve exchange used by classic PGP and by most email today.
Can I send quantum-safe email with this?
Yes, indirectly, and that is the point. PQCServer does not replace your mail provider — you encrypt the content here, get a shortlink, and paste that link into an email sent from whatever address you already use. The mail server, its relays and its backups only ever carry the link. This works with Gmail, Outlook, a corporate Exchange, or anything else, and the recipient needs no account with your provider or with us.
Does the recipient need to install anything?
No. They open the shortlink in any browser and decrypt there. Nothing is installed, and no account is required to read a message that was encrypted to a public key they already hold. This is the main practical difference from Signal, iMessage, Tuta or Proton, all of which protect you only when both parties are inside the same platform.
Can PQCServer read my messages?
No. Encryption and decryption both happen in the browser, and the ML-KEM private key is never transmitted. The server stores ciphertext it has no means of opening — which also means it cannot produce your plaintext under legal compulsion, because it does not hold the key. The technical manual documents the full key handling.
What is ML-KEM?
ML-KEM (Module-Lattice-Based Key-Encapsulation Mechanism) is the post-quantum key encapsulation standard NIST published as FIPS-203 in August 2024, derived from the CRYSTALS-Kyber submission. Its security rests on the hardness of the Module Learning With Errors problem, for which no efficient quantum algorithm is known.
How is this different from Signal?
Signal has been post-quantum since PQXDH in 2023 and strengthened it with the Triple Ratchet in 2025, so this is not a difference in whether the cryptography is quantum-safe. The difference is reach and lifetime: Signal secures an ongoing conversation between two people who both install Signal, with forward secrecy across the whole thread. PQCServer secures a single message to someone who is not on your platform, delivered through a channel you do not control. For a continuing private conversation, use Signal. For the message you have to get to a client, a lawyer or a source today, use this.
What happens to a message after it is read?
You choose. Set a TTL so it expires on its own, or enable burn-after-read so it is deleted from the server the moment the recipient opens it. Attachments follow the message and disappear with it. If you need a file to persist instead, put it in the encrypted vault, which has no expiry.
How much does it cost?
Nothing. Encrypting and sending is free and works without an account. Registering a username is also free and adds a public profile so people can message you without knowing your key in advance. There is no paid tier, no tracking and no advertising.
Start encrypting in 30 seconds
No installation. No credit card. Generate your post-quantum keypair now.