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Let's take an over-the-air update procedure for example. The client which needs updating downloads an update image from the source. It then performs some checksum calculation initially on the received data before proceeding to verify that the data has not been corrupted or tampered with.

What checksum does it compare this calculated checksum to then to verify integrity?

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  • Are you sure you're talking about a checksum? Updates can also be digically signed, in which case they're verified with a public key of the manufacturer. This key can be permanently embedded into the client device.
    – Ja1024
    CommentedMar 26 at 0:45
  • @Ja1024 In this case I am only considering a checksum. Not the digital signature to confirm ownership.
    – Engineer999
    CommentedMar 26 at 5:48
  • A simple checksum like CRC32 cannot be used to detect data manipulations (which you said is one of the goals). It can only detect accidental corruption to some extend. If this is the goal, the reference checksum can be transmitted together with the files. Alternatively, the client could establish a secure connection to the file provider (e.g., via TLS), so that the files are protected in transit.
    – Ja1024
    CommentedMar 26 at 6:03
  • @Ja1024 Yes let's just say that we're looking for accidental data corruption. When you say that the checksum can be transmitted together with the files, so this would be in a separate file? Let's just say for a very simple example, I want to download a simple binary file and verify that it's contents haven't been accidentally corrupted. Could I even include the checksum inside the file, like at the end or at the beginning for example?
    – Engineer999
    CommentedMar 26 at 7:56
  • If the file format supports a built-in checksum, yes, it can be part of the file. Otherwise, it can be a separate file or be transmitted as metadata (e.g., in an HTTP response header).
    – Ja1024
    CommentedMar 26 at 9:55

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