KyNotes is a self-hosted, zero-knowledge note service. The server stores metadata and ciphertext; clients encrypt and decrypt notes, attachments, and container keys.

Report security vulnerabilities privately to the maintainer through GitHub Security Advisories: https://github.com/Busness-app/kynotes-server/security/advisories. Do not open a public issue. Include the affected area, reproduction steps, impact, and affected versions. We will acknowledge reports within two business days and coordinate a fix and disclosure.

• The server can see routing metadata, object versions, sizes, timestamps, and membership metadata. It must not receive plaintext note or attachment data, private encryption keys, or recovery codes.
• Device keys and container keys are wrapped for authorized devices. Revoking a device removes server-side envelopes, but cannot recall plaintext already downloaded or guarantee local-memory and browser-storage wiping.
• Team membership changes rotate keys for future content. Removed members may retain content they already downloaded.
• Deterministic attachment encryption may reveal that two ciphertexts are equal. This is an intentional deduplication trade-off.
• Public publishing is deferred. The initial release does not expose plaintext through the server. A future publisher must use an explicit client-mediated export and a separate public storage model.
• Push payloads contain notification metadata only. Clients pull ciphertext over HTTPS.

• Run the service behind HTTPS. Do not introduce a default that silently downgrades to cleartext.
• Keep the single data directory and its backups private. It contains the database, ciphertext blobs, key envelopes, sessions, and audit records.
• Stop the server before copying the data directory. Restore it while stopped, then run a database integrity check.
• Configure quotas and rate limits for login, pairing, uploads, and notifications.
• Logs must contain only opaque IDs, operation types, coarse timings, and privacy-safe outcomes. Never log plaintext, keys, recovery codes, tokens, or full encrypted payloads.

Changes to authentication, sessions, device enrollment or revocation, recovery, key envelopes, authorization, sync conflict handling, attachment storage, or logging require tests for both the expected path and the relevant failure or attack path. Review the verification strategy in DESIGN.md.

• DESIGN.md — architecture, encryption, storage, and deployment
• LOGGING.md — privacy-safe logging rules
• CONTRIBUTING.md — contribution and review requirements