How OTDrop protects your file

When you send a file, your browser generates a fresh per-transfer content-encryption key from strong cryptographic entropy. Your file and any short note you attach are encrypted inside your browser before they are uploaded. The plaintext never leaves your device.

The content-encryption key is wrapped with a master key held by the service and stored next to the ciphertext. The recipient's browser unwraps it after the recipient proves they are the intended person, then decrypts the file locally. We cannot read the plaintext of transferred files or messages.

When you address a transfer, you tell us the recipient's email address. You can optionally set a passphrase that the recipient must enter before the file unlocks. If provided, the passphrase is converted to a salted one-way hash in your browser — we store the hash, never the original text.

At claim time, if a passphrase was set, the recipient enters it; we compare it against the hash using a constant-time equality check. If it matches, access is granted and the hash is wiped from our database. If no passphrase was set, the recipient can claim the file with just the pickup link.

Every transfer is single-use. Ciphertext is deleted from our storage on the first successful download or seven days after creation, whichever comes first. After deletion, no party — including us — can reconstruct the file.

Senders can revoke any unclaimed transfer from their dashboard. Revocation invalidates the pickup link and schedules immediate ciphertext deletion.

Every connection between your browser, our service, and the providers that support it is encrypted in transit using modern TLS. Ciphertext at rest is further protected by the per-transfer key wrapping described above, so possession of the encrypted blob alone is not enough to read the file.

Senders authenticate with an established third-party identity provider. We never see your password. Sessions are short-lived and use secure, same-site cookies. Abuse-sensitive operations are protected by rate limits, a bot-challenge step, and audit logging; repeated abuse results in account suspension.

OTDrop is not a managed secure-delivery platform. It does not offer long-term retention holds, recipient identity assurance beyond passphrase knowledge, auditable chain-of-custody, data-residency contracts, or formal compliance attestations. If your workflow requires any of those, do not use OTDrop — pick a product built for that job.

Client-side encryption protects your file in transit and at rest in our storage. It does not protect against a compromised endpoint: malware on the sender's or recipient's device, a hostile browser extension, or physical access to an unlocked screen can defeat any file-transfer tool, OTDrop included.

A passphrase is only as strong as the channel used to share it. For a very high-risk handoff, share the passphrase in person, by phone call, or through a separate secure channel — not in the same email thread as the pickup link.

If you believe you have found a security issue in OTDrop, please write to security@otdrop.com. We read every report and reply to credible ones within a few business days. Please do not test against accounts or transfers you do not own.

See also our security.txt and the privacy policy.