ambassador at fourthworld.com
Thu Apr 24 11:57:49 EDT 2014
Martin Baxter wrote:
> What you say is obviously true, there is no ultimate guarantee from
> The checksum is not useless though. It gives pretty good confidence
> that the file didn't get altered in transit, whether by a network
> error, a disk writing error, or by the intervention of a malcious
> actor as MITM replacing the requested file with a doctored version
> of their own. It may not provide ultimate trust but is better than
> no checks at all.
> Some places sign their downloads with PGP, which in theory gives a
> stronger guarantee of authenticity. However I think there are similar
> issues with that. To verify it, you must install the public key of the
> signer and assert (but on what basis?) that it is strongly trusted.
> Here too, if the malicious actor can subvert both the download file
> and the public key, the method fails. Most downloaders don't know
> anything about the signer or have prior knowledge of his/her public
> key and may not see anything amiss if they are somehow subverted.
> It gets better I suppose once you have had a trusted key in your
> keyring for a while and it has a good track record of vouching for
> software that you have confidence in. However, if the key that you
> originally installed and more or less blindly trusted was actually
> a fraud, then you are in trouble.
Very helpful, Martin. Thanks for that.
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