Re: signed gcc downloads

[Zach Bagnall <zach dot bagnall at bulletinwireless dot com>]

On Fri, 2002-07-19 at 01:50, Paul Koning wrote:
> Those aren't signatures, they are only checksums.  It isn't clear from
> Zach's note which he's looking for -- the question depends on what
> danger you want to protect against.
> 
> A simple MD5 checksum protects against data corruption in transit (TCP
> checksum does the same, but not as well).  It does not protect against
> tampering with the file because it's easy to post an md5.sum file
> with corresponding changed checksums.
> 
> A signature (e.g., PGP signature) protects against tampering too, but
> you need the signer's public key to check it, and it's more hassle to
> apply since the signer has to supply his private key to do so.
> 
>       paul

Yes, it is a bit of a hassle, but I think its worth it.

http://www.gnupg.org/

For example, the linux kernel, irssi and openssl all use signed
downloads. Each file comes with a corresponding .sig file that is
generated using the signers private key.

If a distribution server is cracked and the file is altered, the
attacker will be unable to generate a valid signature for the altered
file (unlike an md5 sum). Recently irssi was backdoored by an attacker -
a digital sig would have enabled users to detect the alteration. The
irssi developer is now signing all files.

Incidentally, this email is also signed :-).

-- 
Zach Bagnall <zach.bagnall@bulletinwireless.com>

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