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Is my CloudStor FileSender data secure? Can I encrypt the data?

FileSender supports full end-to-end encryption using the industry standard AES-256 encryption [1]. All encryption and decryption happens in the Web browser, no additional software is required.

With end-to-end encryption your file is encrypted in your web browser before it is transmitted from your computer. The recipient of the file then downloads the encrypted data and, using the passphrase or generated key provided by you, can decrypt the files in their web browser. Without knowing the key nobody can ever read the files (not even AARNet).

As well as the confidentiality offered by encryption, the encryption process also uses GCM mode [2] to protect the integrity of encrypted files. This way every bit of information you encrypt is known to be exactly the same when the data is decrypted or the decryption will fail. The integrity check is bound to the encryption operation, so once data is encrypted in your web browser it can not be modified anywhere on the network without detection.

To use encryption check the "File Encryption" box on the upload page. Enter a unique password that you can send to the receiver after uploading and sending your files. We advise you do this via a different channel than e-mail, for example by telephone or SMS. As soon as the receiver enters this password they can download the files. The encryption and decryption of files is done by the browser during uploading and downloading.

Note that encryption may impact your upload and download speeds.  Because files are encrypted and decrypted in the web browser, files greater than 4GB may not upload or download.

[1] https://en.wikipedia.org/wiki/Advanced_Encryption_Standard
[2] https://csrc.nist.gov/publications/detail/sp/800-38d/final