How SendSecure works
SendSecure is a privacy-first service for sending encrypted messages and optional file attachments that automatically delete themselves after viewing or expiry.
Everything is encrypted directly inside your browser before it is sent to our servers. Your plaintext message, password, and original file contents never leave your device.
The server receives only ciphertext plus the salt and initialization vector needed for later browser-side decryption. Your password is never uploaded and is not stored anywhere.
After creation, you receive a one-time link. The recipient enters the same password and decryption happens entirely in their browser. Once the payload is successfully decrypted, the encrypted server copy is permanently deleted.
Encryption standards
SendSecure uses modern, industry-standard cryptography:
- AES-GCM with 256-bit keys encrypts message and file data while also checking that the ciphertext was not altered.
- Argon2id, a memory-hard password key derivation function, turns your password into the encryption key.
- Every message and file uses unique, cryptographically random salts and initialization vectors.
- Encryption and decryption use the WebCrypto API and a browser-side Argon2id implementation. Nothing is decrypted server-side.
Without the password, the stored ciphertext is designed to remain unreadable—even to the server operator.
File attachments
You can attach a file up to 25 MB. It is encrypted separately with its own AES-GCM IV and salt-derived key, keeping message and file encryption isolated.
The recipient decrypts the file in their browser after unlocking the link. Following successful retrieval, the file is removed from the server and cannot be downloaded again.
Retention and one-time access
SendSecure does not collect personal information, run analytics, or use tracking cookies. Only encrypted message and file blobs are temporarily stored—never plaintext or passwords.
One-time access reduces the risk of sensitive information being reopened, forwarded, or left accessible online. If a payload is never opened, it is automatically deleted after the selected expiry period of 1–7 days.