Security

TL;DR: CookieVault encrypts cookies on your device with Argon2id-derived keys and XChaCha20-Poly1305 before they ever reach our servers, so sync is zero-knowledge — we store ciphertext we cannot read. The code is open-source and auditable, with responsible disclosure, a bug bounty after 10,000 installs, and an independent audit planned for Q3 2026.

Security at CookieVault is the practice of ensuring that the data you trust to the product — chiefly the cookies you sync between devices — cannot be read by anyone but you, including us. The product achieves this with end-to-end encryption: keys are derived on your device from a passphrase we never receive, cookies are sealed before they leave the browser, and the cloud stores only opaque ciphertext.

Encryption architecture

In short: A passphrase is stretched into a key with Argon2id (memory-hard, the 2015 Password Hashing Competition winner standardized as RFC 9106), and each cookie record is sealed with XChaCha20-Poly1305 from libsodium. A per-device key enables fast unlock so the passphrase is only needed when enrolling a new device.

Argon2id is the memory-hard key-derivation function that won the Password Hashing Competition and is now standardized as RFC 9106, chosen specifically to make brute-forcing a stolen ciphertext store expensive.¹ XChaCha20-Poly1305 is an authenticated encryption construction with a 192-bit nonce, provided by libsodium, a portable cryptography library used across the industry.²³

Open source and auditability

In short: The extension, the sync server, and this website are MIT-licensed and public. The cryptographic boundary is in code you can read, and store releases are reproducible-built from tagged Git commits so you can verify the binary matches the source.

How you can independently verify the claims:

1. Read the source — the client and server are public on GitHub under the MIT license
2. Locate the crypto boundary — find where plaintext cookies become ciphertext before any network call
3. Check the tagged release — every Chrome Web Store version maps to a Git tag
4. Reproduce the build — run the documented build to regenerate the artifact
5. Compare hashes — match the store binary’s SHA-256 against the tagged CI artifact

This is what “auditable” means in practice: not a promise that the code is secure, but the ability for anyone to check it. Reproducible builds close the gap between “the source looks safe” and “the binary I installed is that source.”

Vulnerability disclosure

In short: Email security@cookievault.net, optionally PGP-encrypted using the key at /.well-known/pgp-key.txt. We run a 90-day coordinated-disclosure window, accelerate for active exploitation, and publish an advisory for every fix.

Our disclosure commitments:

• Contact — security@cookievault.net, with a machine-readable pointer at /.well-known/security.txt
• Encryption — PGP public key published at /.well-known/pgp-key.txt (fingerprint added before launch)
• Timeline — 90-day standard coordinated-disclosure window, accelerated for actively exploited issues
• Transparency — a public security advisory accompanies every fix
• Credit — researchers are credited unless they prefer to remain anonymous

A 90-day window aligns with the de-facto industry norm popularized by Google’s Project Zero, which balances giving vendors time to fix against leaving users exposed.⁴

Bug bounty and audits

In short: A paid bug-bounty program starts at 10,000 installs, when payouts are sustainable; until then researchers get public credit. An independent third-party security audit is planned for Q3 2026, and we will publish its report and our remediation.

Sequencing the paid bounty after 10,000 installs is a deliberate, honest constraint: a credible bounty needs a budget that can pay out reliably, and we would rather credit researchers transparently now than advertise a bounty we cannot yet fund.

See also

• Privacy policy — what we collect and never collect
• No-sale pledge — our commitment never to sell data
• Open source — MIT license, reproducible builds, contribution guide
• Editor — the extension whose sync this architecture protects