DC Relay help

DC Relay is the service for exchanging engineering data such as CAD models, drawings and specifications securely. A service of Digital Crafted GmbH.

1. Overview

A delivery is one or more files sent to one or more recipients, with a subject and optionally a project, reference and message. DC Relay checks every file (checksum and malware scan), notifies the recipients by e-mail and logs every step up to the download and the confirmation of receipt.

• Staff of your organisation send deliveries, track them and invite customers.
• Recipients do not need an account: they open the personal link from the e-mail. An account is only required for strictly confidential deliveries.
• Customers with an account see all deliveries addressed to them in their Inbox.

Accounts are by invitation only. There is no open registration. The operator sets up organisations, their administrators invite staff, and staff invite customers. Only staff of an organisation can send. Customer accounts can only receive.

The interface is available in German and English (switch at the top right or under Account), in light and dark design, and works on PC, tablet and phone.

2. Receiving a delivery

With the link from the e-mail

1. Open the link directly from the e-mail. It is personal and only valid for your address. Please do not forward it.
2. For confidential deliveries, request a verification code. It is sent to the same address and is valid for 15 minutes.
3. Download the files one by one. Each file shows its SHA-256 checksum.
4. If the sender asks for it, confirm receipt after downloading. The sender sees this immediately.

If the part after the # is missing from the link, it was cut off while copying. Please open it directly from the e-mail. If a link no longer works, the sender can send a new one; the old one then stops working.

Checking the checksum

This confirms the file arrived unchanged. On Windows in PowerShell:

Get-FileHash .\file.stp -Algorithm SHA256

On macOS or Linux: shasum -a 256 file.stp. The value must match the one shown in DC Relay.

In the inbox (with an account)

After signing in, the Inbox lists all deliveries to your address, from all organisations, with the state New, Downloaded or Confirmed. Click one to see the details and files. Confidential and strictly confidential deliveries only open in the inbox once your account uses two-factor sign-in. Until then they show “2FA required”.

3. Creating a customer account

An account is worthwhile if you receive data regularly or need to receive strictly confidential deliveries. You get an invitation in one of two ways:

• By e-mail: open the link, choose your name and a password (at least 12 characters), done.
• By QR code, e.g. during a meeting on site: scan the code with your phone, enter your e-mail address, type in the verification code you receive, then choose your name and password.

An invitation is valid for 14 days and only once. If you already have an account, you receive a note by e-mail instead and simply sign in.

4. Two-factor sign-in

Two-factor sign-in protects your account in addition to the password. It is mandatory for administrators, auditors and everyone who sends. Customers need it to open confidential and strictly confidential deliveries in their inbox.

1. Install an authenticator app, e.g. Microsoft Authenticator, Google Authenticator, 2FAS or Aegis.
2. Under Account, choose “Set up two-factor sign-in” and scan the QR code.
3. Enter the 6-digit code from the app.
4. Store the recovery codes shown safely. Each code replaces the app once if your phone is missing.

Lost your phone and have no recovery codes left? An administrator of your organisation can reset two-factor sign-in.

5. Sending a delivery

1. Recipients: type a name or address. Saved contacts and previous recipients are suggested. You can paste several addresses at once, separated by comma, semicolon or line break. With “+ Add CC” further people receive a copy.
2. Enter a subject. Optional: project, your reference (order, request or drawing number) and a message.
3. Drag in files or use “Choose files” or “Choose folder”. For folders the path becomes part of the file name, e.g. Assembly_A_Part1.stp.
4. Choose the confidentiality and availability period. Optionally request a confirmation of receipt.
5. Send. Upload, check and delivery run automatically. Progress is shown in three steps.

Uploads keep running in the background while you open other pages. A panel at the top right shows speed, remaining time and history. Single files can be paused, resumed or cancelled.

Upload interrupted, e.g. by a network change? Open the delivery and choose the same file again. Only the missing parts are transferred.

With Send again on an earlier delivery you reuse its recipients, subject, project and settings for a new delivery. You choose the files again.

6. Confidentiality levels

Your organisation can set shorter periods. Strictly confidential deliveries can only go to recipients with an account. Anyone without one is named when you send and can be invited under Invite customers.

7. Tracking deliveries

The Deliveries list shows all deliveries of your organisation. Filter by period, status, project or only your own. The search finds number, subject, reference and recipient. Export downloads the selection as a CSV file for Excel.

Click a delivery to see the details: who downloaded what and when, the state of each file and the available actions.

• Resend link: for a recipient who cannot find the e-mail. The old link stops working.
• Withdraw: ends a delivery immediately. All links stop working and the files are deleted.
• Manifest: list of the files with size and SHA-256 as a JSON file.
• Proof of delivery: per recipient, when each file was downloaded and when receipt was confirmed.

8. Address book

The address book is shared across the organisation. Save a name, company and note for an address. Previous recipients without an entry are listed below and can be added with one click. “Send” starts a new delivery to that contact.

9. Inviting customers

1. Under Invite customers, optionally enter name and company.
2. For an invitation by e-mail, enter the address and keep “Send invitation by e-mail” ticked.
3. For a QR code, e.g. in a meeting on site, leave the address empty. The customer then confirms their address with a code.
4. Link and QR code are shown only right after creation. You can copy or print them.

The list shows which invitations are open, accepted, expired or withdrawn. Open invitations can be withdrawn.

10. Requesting files

A file request brings data to you: you send a customer or supplier a link and they upload the files without an account. The data arrives checked, as an order of yours.

1. Under Request files, enter the e-mail of the person who should upload, a subject, and optionally a reference, project and a message saying what you need.
2. Choose the confidentiality and how long the link is valid (at most 14 days).
3. “Send request” sends the link by e-mail. Without e-mail the link is shown only once; copy it and pass it on yourself.

The person opens the link, sees your message, uploads files or whole folders and clicks “Hand over files”. Interrupted uploads resume when they pick the same file again. As with sending, every file is checked with SHA-256 and scanned for viruses.

You are notified as soon as the files are ready. The order appears under Orders, marked “Received by file request” with the person's address. The same rules apply as for every order, including deletion after 30 days.

The link works for exactly one hand-over. After that, after expiry or when you revoke the request, it stops working. The list shows whether the link was opened and which order it produced.

11. Administration (for administrators)

• Overview: state of processing, malware scan and storage, usage over the last 30 days and the rules in force.
• Users: invite colleagues, change roles, block, remove, reset two-factor sign-in, resend invitations. The last administrator cannot be demoted or blocked.
• Projects: create, rename and archive codes and names. Archived projects stay visible on old deliveries.
• Log: every sign-in, delivery, download and change, filterable by area and period and exportable as CSV.

12. Accounts, organisations and operation

Nobody can sign up on their own at DC Relay. Every account starts with an invitation:

1. The operator creates an organisation (e.g. a company) and invites its first administrator.
2. The organisation's administrator invites staff and assigns roles. Only staff can send.
3. Staff invite customers. Customers can only receive; they see their deliveries in the inbox.
4. Recipients without an account simply use the link from the e-mail. File requests cover the way back.

If two companies regularly exchange data in both directions, the other company can get its own organisation with its own administrator. Organisations stay strictly separated. The operator can set allowed e-mail domains for an organisation; then only staff with those addresses can be invited.

What the operator sees

The operator of the service has an Operations area. It shows all organisations, orders, users and the audit log, to detect misuse and run the service securely. It shows metadata only: who sent what to whom and when, subjects, file names and sizes. The operator cannot open file contents through DC Relay.

The operator can intervene: block an organisation or a user, or revoke an order. Every intervention needs a reason and is recorded in the audit log of the affected organisation, visible to its administrators and auditors.

System health (Operations → System)

A separate watcher measures every 2 minutes: the server (CPU load, temperature, memory, system disk, on a Raspberry Pi also under-voltage), the data disk, the database, whether the application and the background worker run, the queue, the system services, the virus scanner and mail. Operations → System shows the result as a traffic light with the last 24 hours.

• Thresholds: warning from 70 °C, 80 % disk and 85 % memory; critical from 82 °C, 92 % disk and 95 % memory.
• Other computers such as the edge proxy, an AI machine or a NAS are added by the operator with address and port. The server checks that the port is open or (with HTTP check) that it answers. “Important” turns an outage into a critical state.
• Alert mail only when the overall state changes (fine, warning, critical) and on the all-clear, not on every measurement.
• If no measurement arrives for 10 minutes, the page shows critical: then the watcher itself is not running.

The page shows measured values only, no files and no customer data. Values are deleted after 14 days.

13. Deletion and backup

Every delivery is deleted automatically and permanently at the latest 30 days after it was created, earlier if a shorter availability period was chosen. Withdrawn or cancelled deliveries are deleted immediately.

There is no backup of transferred files. A deleted file therefore cannot be restored, not even by the operator. DC Relay is a transfer channel, not an archive: please keep your originals in your own systems and store received data after downloading where your organisation requires it.

Only evidence without file content is kept: delivery data (number, subject, recipients, file names, sizes, checksums) and the log. Even after deletion it shows who sent and received what and when. Log entries are deleted automatically after 4 years; younger entries cannot be changed or deleted by anyone, the operator included.

Deletion after 500 days without activity

An account that has not signed in for 500 days is deleted automatically. So is an organisation in which nobody signed in and no order was created for 500 days. This way no orphaned accounts and data are left behind.

• For an account, this deletes the sign-in data, two-factor settings, memberships and the orders the person sent.
• For an organisation, this deletes all accounts that belong only to it, the address book, projects, invitations, file requests and all orders including files.
• Warning mails come first: 4 weeks, 3 weeks, 2 weeks, 1 week, 3 days and 1 day before the date, stating the deletion date. For an organisation they go to its administrators.
• To stop the deletion, simply sign in. For an organisation, it is enough that one member signs in or an order is created.
• After deletion a new invitation is needed; an organisation is set up again by the operator.

The operator can also delete accounts and organisations for good by hand, for example when a contract ends. This needs a reason and typing the name to confirm.

14. Security and privacy

• Transfer is always encrypted (TLS). Data is stored on encrypted disks.
• Every file is checked for completeness with SHA-256 and scanned for malware before anyone can download it.
• Links are personal, time-limited and stored only as a hash. A new link invalidates the old one.
• Sign-in with password and two-factor code. Too many failed attempts lock the account temporarily.
• Every action is logged. Administrators and auditors of your organisation can view the log.
• Organisations are strictly separated. No member of one organisation sees another organisation's deliveries. The operator sees metadata only, never file contents (see section 12).

15. Terms of use

Before first use you confirm a summary of the terms of use (half a page). With an account this happens once, right after sign-in; as the recipient of a link or when uploading through a file request, with a checkbox on the page. DC Relay cannot be used without confirming. If the terms change, you are asked again on your next sign-in.

The full texts (terms of use, privacy notice and the data processing agreement for organisations) are public under Legal. Every confirmation is recorded in the log with time and version.

16. FAQ

I did not receive an e-mail.

Please check your spam folder. The sender can resend the link under Deliveries.

The verification code is not accepted.

A code is valid for 15 minutes, and only the most recently requested one. Request a new one. After several failed attempts you have to wait briefly.

“This delivery is no longer available.”

The delivery has expired, been withdrawn, or the maximum number of downloads has been reached. Ask the sender to send it again.

Can I get a deleted delivery back?

No. There is no backup of the files (see section 11). The sender has to send the files again.

How large may files be?

Even very large CAD data is possible. Files are transferred in parts, so an interruption only costs the missing remainder. A quota of your organisation may limit the total volume.

I forgot my password.

Choose “Forgot password?” on the sign-in page. The link is valid for 30 minutes.

How do I reach the team with questions, bugs or ideas?

Use Feedback in the sidebar. Choose the type (question, bug, improvement, other), write your message and send it. It goes straight to the operator, without a mail program. The answer comes by e-mail to your address. Please do not include confidential content or passwords.

DC Relay is a service of Digital Crafted GmbH.