How to get your first key signed

Peter Lebbing peter at digitalbrains.com
Thu Oct 1 14:32:37 CEST 2015


On 01/10/15 13:08, Bob Henson wrote:
> If the program has been altered the signature will fail, will it not?

Well, first of all, a checksum is not a cryptographic hash. It has
different properties: a checksum usually has no collision resistance.
Which is why the designers of WEP should have never chosen CRC-32 to
protect their data, especially since said data was encrypted with a
stream cipher[1]. Anyway, it was not the most important shortcoming of
WEP, so it doesn't truly matter ;).

And a signature by a key has a lot of extra information that simply
putting a hash value on the website where you offer the download does
not have. Just a hash value on the website does not tell me who
calculated that hash value, and whether there is some MITM between me
and the website.

Peter.

[1] Stream ciphers allow you to flip single bits in the plaintext. And
when I flip a bit in a piece of data, I know exactly which bit I need to
flip in the CRC-32 checksum to make the checksum correct again. So the
CRC-32 was completely useless for protection against malicious bitflips
in the plaintext it was supposed to protect.

-- 
I use the GNU Privacy Guard (GnuPG) in combination with Enigmail.
You can send me encrypted mail if you want some privacy.
My key is available at <http://digitalbrains.com/2012/openpgp-key-peter>



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