Encrypted file transfer: what matters

Why a normal email is not enough

Today an email is usually protected by transport encryption on its way between mail servers. This prevents anyone from reading along on the connection. On the servers themselves, however, messages and their attachments are generally readable: at your own provider, at the recipient's provider and in all backups. Anyone who gains access to one of these mailboxes sees all attachments, often for years.

On top of that, an email cannot be recalled. One typo in the address, and the documents sit in the wrong mailbox. For confidential content you therefore need more than protection of the connection.

With personal data there is also the legal side. The GDPR requires appropriate technical measures to protect data and explicitly names encryption as an example. What is appropriate in a given case depends on the type of data. For health data, personnel files or financial documents, the requirements are higher than for a flyer draft.

Transport encryption and file encryption

When sending files, it is worth distinguishing two kinds of encryption:

• Transport encryption (TLS, recognizable by “https”) protects the data only on its way. At the destination it arrives decrypted.
• File encryption makes the file itself unreadable. It stays encrypted even when it is stored, and only becomes readable again for the authorized recipient.

For confidential documents, both should come together. Fairsend uses both: files are encrypted with AES-256-GCM in your browser before they leave your device, and in addition the whole connection is TLS-encrypted. On the servers in Germany, the files are stored only in encrypted form. The key is stored separately from them, also encrypted.

The common options at a glance

There are several ways to send files encrypted. They differ mainly in how much effort they require from the recipient:

• Encrypted ZIP archive: with an archiving program you create an archive with a password and AES encryption. This works well as long as the recipient has a suitable program and you pass on the password separately. Make sure to use AES, as the older ZIP encryption is considered weak.
• Email encryption with certificates or key pairs: very secure, but both sides must have set it up. With new contacts this often fails.
• Encrypted file transfer by link: you upload the file, and the recipient opens a link in the browser. They need neither a program nor an account.

For everyday dealings with clients, customers or applicants, the link is usually the most practical way, because the recipient does not have to set anything up.

Send the password and the link separately

A password only protects a transfer if it is not in the same message as the link. Share it by a second route: by phone, by SMS or in person. That way it is not enough to intercept the email or forward it by mistake.

With Fairsend, you can add a password to a transfer on the paid plans. Alternatively, the email code requests a one-time code at download, which is sent to the recipient's address. This way only someone with access to that mailbox can open it, and you do not have to pass on a password.

Periods, download limits and deletion

The shorter a file is available, the smaller the risk. So set a period that suits the occasion, for example a few days for a signature. Limit the number of downloads if only one person needs the file, or have the transfer deleted after the first download.

Fairsend deletes transfers automatically and irrevocably when the period ends. There is no recycle bin and no restore. On the free plan, a transfer stays available for 7 days and is deleted after the first download.

Tracing who received what

Especially with important documents, you want to know whether they arrived. Fairsend shows the status of every transfer and notifies you as soon as it has been downloaded. When a download starts, the time, IP address and recipient are logged and combined with the SHA-256 checksums of the files into a proof of delivery. This lets you prove later which file was retrieved and when.

The plans for teams add an audit log, the four-eyes principle for sensitive transfers and a Geo-Lock for downloads.

What encryption cannot do

Encryption protects files in transit and on the server. It does not protect against every risk. Anyone who has the link and, if applicable, the password can open the file. So send the link only to the right address and check addresses before sending, especially with names that look similar.

The devices on both sides also play a role. If a computer is infected with malware, the best encryption during sending helps little. Keep your operating system and browser up to date and do not save downloaded documents to public folders. After the download, the file is unencrypted at the recipient, and they are responsible for its further storage.

For teams and sensitive areas

In law firms, medical practices, HR departments or public authorities, internal rules for sending often apply. Features that go beyond the individual transfer are then helpful: a shared team account with roles, an audit log that records who sent what and when, and the four-eyes principle, where a second person approves a transfer. Which obligations apply to your data is best clarified with your data protection officer.

Checklist for confidential files

• The file is encrypted before the upload, not only on the way.
• The recipient needs no program of their own and no account.
• Password or one-time code, with the password always sent by a second route.
• Short period and limited downloads, then automatic deletion.
• Proof of when which file was retrieved.