What ZipPigeon handles
ZipPigeon needs some delivery details to work: account emails, recipient emails, timestamps, file sizes, transfer status, download counts, audit events, IP addresses, user agents, and abuse-prevention signals.
Security
How ZipPigeon protects your files
See how ZipPigeon uses XChaCha20-Poly1305 file encryption, X-Wing hybrid recipient keys, dual signatures, and client-owned private metadata.
What stays out of reach
File contents, filenames, private transfer titles, and notes are encrypted in the client before upload. Account-bound transfers and manually delivered secure links keep raw file keys, private account keys, recovery codes, and URL-fragment secrets out of normal server requests.
Technical security details
File data uses chunked XChaCha20-Poly1305 authenticated encryption with random 256-bit payload keys and encrypted manifests. Password-protected private-key bundles use Argon2id. Migrated v3 recipients use X-Wing draft-10 HPKE - X25519 + ML-KEM-768 with HKDF-SHA-256 and ChaCha20-Poly1305 - for payload-key envelopes.
How account sharing works
V3 account recipients use hybrid X-Wing key envelopes and Ed25519 + ML-DSA-65 dual-signed grants that bind the recipient, key fingerprint, envelope, upload, and expiration. Both signatures must verify, legacy formats remain readable during migration, and a v3-capable recipient is not silently downgraded.
How secure links work
Secure links are useful for quick guest access. They are bearer access: anyone with the full active link may be able to open the transfer. A manually delivered link keeps its URL-fragment secret out of ordinary navigation requests. Current automatic guest-email delivery relays the complete URL through the backend and is not part of the zero-knowledge claim.
Apple Shortcut retired
The server-assisted iOS Shortcut path is retired because it staged plaintext before encryption. Its intake and approval endpoints return Gone. Use the browser or standalone client so encryption happens before ZipPigeon receives file bytes.
Revocation and deletion limits
Revocation, expiration, and archive stop future service-mediated access. They cannot recall files already downloaded and decrypted. Archived transfers attempt encrypted-object deletion, and operational records or backups may remain for security, reliability, or abuse-response needs.
Metadata boundaries
Private transfer titles and notes live in the client-encrypted signed manifest, and the deployment-owned database key is retired. Account emails, recipient routing, sizes, timestamps, status, authorization relationships, public workflow labels, and audit structure remain visible because the service needs them to operate.
Audit status
ZipPigeon has security smoke tests and documented crypto design notes. It should not be described as SOC 2, HIPAA, ISO 27001, or independently audited until those assessments are completed for the deployed service.
Still on the roadmap
Public key transparency, hardware security modules, enterprise SSO enforcement, custom enterprise branding, bring-your-own infrastructure, data residency guarantees, formal compliance attestations, customer-managed keys, and independent cryptographic review remain future work. Post-quantum v3 availability still depends on deployment controls and recipient migration.
Vulnerability reports
Send security reports to security@zippigeon.com with affected routes, reproduction steps, impact, and synthetic evidence where possible.
Send the file. Keep control of the link.
Use ZipPigeon when a file needs to reach the right person without becoming another attachment or shared folder to clean up later.
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