Are Time Machine backups over WiFi encrypted in transit?

I asked this a couple days ago in the thread for the Mac Mini episode, but I’m asking now in its own thread. David and Stephen mentioned doing Time Machine backups over WiFi. Does anyone know if those backups are encrypted in transit? Right now I occasionally plug a backup drive into my MacBook Pro at the office. I’d love to wirelessly backup to a drive on my iMac, but don’t want to use the office WiFi if those TimeMachine backups aren’t encrypted in transit (I keep my personal records on the MacBook).

If you’re using a secure WiFi (I.e. have to use a WiFi key to connect) the traffic would be encrypted end-to-end. Now, if you really distrust the WiFi provider then a man-in-the-middle attack could still snoop the traffic. But if you trust the WiFi provider not to do that you should be ok.

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It really depends on how TimeMachine over the network works but I think that the backups are encrypted in transit if the backup itself is encrypted. The reason that I think this is that if the backup password is not known to the server then there is no way for the server to do the encryption: the sparse bundle that contains an encrypted backup has to be mounted over the network by the client machine. In that case anything written to it would have to be encrypted prior to transmission.

This is only (reasonably well reasoned) speculation though, so it’d be something to verify before jumping in. Depending on the natuture of your WiFi network security, it may not even be possible regardless.

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Thanks for the replies. All the points make sense, now that I think about it.

Most work places make it clear that there is no expectation of privacy for users on their “system”, and they usually define networks as belonging to their system. In some workplaces, if you are monitored doing encrypted transmissions between “foreign” devices, there may be consequences. So, check with your IT security officer before assuming how the data transmission will be handled.

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