Problem with checksums

[kladis]

While trying to verify the checksums i executed the following commands as stated to the handbook:

gpg --keyserver subkeys.pgp.net --recv-keys 96D8BF6D 17072058 2D182910 239C75C4 D8BA32AA 7DDAD20D

OUTPUT: ... gpg: Total number processed: 6
gpg: unchanged: 6

And then:
gpg --verify install-amd64-minimal-20130516.iso.DIGESTS

OUTPUT:
gpg: Signature made Fri 17 May 2013 09:56:53 AM EET using RSA key ID 2D182910
gpg: Good signature from "Gentoo Linux Release Engineering (Automated Weekly Release Key) <releng@gentoo.org>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: 13EB BDBE DE7A 1277 5DFD B1BA BB57 2E0E 2D18 2910

Also:
sha1sum -c install-amd64-minimal-20130516.iso.DIGESTS.asc
OUTPUT:
sha1sum: install-amd64-minimal-20130516.iso.DIGESTS.asc: no properly formatted SHA1 checksum lines found

sha256sum -c install-amd64-minimal-20130516.iso.DIGESTS.asc
OUTPUT:
sha256sum: install-amd64-minimal-20130516.iso.DIGESTS.asc: no properly formatted SHA256 checksum lines found

sha512sum -c install-amd64-minimal-20130516.iso.DIGESTS.asc
OUTPUT:
install-amd64-minimal-20130516.iso: OK
install-amd64-minimal-20130516.iso: FAILED
install-amd64-minimal-20130516.iso.CONTENTS: OK
install-amd64-minimal-20130516.iso.CONTENTS: FAILED
sha512sum: WARNING: 20 lines are improperly formatted
sha512sum: WARNING: 2 computed checksums did NOT match

I also tried to download the *.iso file but with the the same result...
What is it wrong with the signatures???
Please help...

[Hu]

Files ending in .asc are detached signatures. You cannot use them with sha256sum. Those signatures attest that the .DIGESTS file is unmodified. If the signature is valid, then and only then should you validate the checksum in the digest file.