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A comment on Creating a bespoke data diode for air‑gapped networks. Parent comment

Re:Creating a bespoke data diode for air‑gapped networks by IncreasePosts on Tuesday January 06, 2026 @02:09PM (#46517005)
How confident are you that a compromised receiving machine able to send arbitrary voltages on 8 of the 9 pins wouldn't be able to trigger some unexpected behavior on the airgapped machine?
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Re:Creating a bespoke data diode for air‑gapped networks by nelop on Tuesday January 06, 2026 @02:18PM (#46517150)
Pretty confident, if the recieving machine is compromised, it is only connected to the opto coupler, that ensures only one way traffic, on one pin.

Somehow you would have to get a receive pin to transmit, and then get through the opto coupler and then it just hits a pin that's designed to only send data.

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Re:Creating a bespoke data diode for air‑gapped networks by justincormack on Tuesday January 06, 2026 @02:25PM (#46517255)
Pins on modern hardware like that are all bidirectional you set the direction in software normally.
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Re:Creating a bespoke data diode for air‑gapped networks by nelop on Tuesday January 06, 2026 @02:56PM (#46517726)
Ohhh that's a good point, you can set the Rx pin to Tx, then it still has to get through the opto isolator, and then it's talking to a port that's set to Tx.
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Re:Creating a bespoke data diode for air‑gapped networks by IncreasePosts on Tuesday January 06, 2026 @02:23PM (#46517227)
Sorry, I didn't mean for your project, but for using a RS232 null modem like OP suggested
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Re:Creating a bespoke data diode for air‑gapped networks by MisterTea on Tuesday January 06, 2026 @08:55PM (#46521561)
What voltages would these be? If the receiver and transmitter are both the same as in the article then I don't see how this is an issue.
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