Knoppix 8.6: Failed to fetch during apt-get update

Hello,

I booted my PC with knoppix 8.6
Then I ran:
sudo apt-get update

I got few messages like the following:
Code:W: GPG error: http://ftp.de.debian.org/debian stable-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0E98404D386FA1D9 NO_PUBKEY 6ED0E7B82643E131
E: The repository 'http://ftp.de.debian.org/debian stable-updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.So I ran:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6ED0E7B82643E131
sudo apt-get update


Then I got:
Code:E: The repository 'http://security.debian.org stable/updates Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.So I added:
[trusted=yes]

to /etc/apt/sources.list

Then I ran:
sudo apt-get update

and got:
Code:E: Failed to fetch http://security.debian.org/dists/sta...-i386/Packages 404 Not Found [IP: 146.75.54.132 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.Can you please tell what is the reason for this ?

Thank you,
Zvika