Checking sources: dscverify and debian-keyring

1 files changed, 37 insertions, 6 deletions

diff --git a/basics.md b/basics.md
index 166b31e..dd43c1b 100644
--- a/basics.md
+++ b/basics.md
@@ -16,21 +16,52 @@ Using `apt-get`:
 Checking the source
 -------------------
 
-Get the key if needed
+This is the trick part. In theory, you could run just
 
-    gpg --recv-keys 12345678
+    dscverify *.dsc
 
-Checking the source
+Which would check if the signature was made for a key included in the `debian-keyring` package.
 
-    dscverify *.dsc
+In practice, it should always work for sources you download from the **same** Debian version you're running.
+But sources you download from newer versions might not work, depending basically if the maintainer's key is
+already on the `debian-keyring` you installed.
 
-Extracting:
+If not, you might try to have a newer copy of the `debian-keyring` somewhere. We already provide one in the
+form of git://anonscm.debian.org/keyring/keyring.git available as a git submodule in the `keyring` folder:
 
-    dpkg-source -x *.dsc
+    gpg --no-default-keyring --keyring /path/to/debian/keyring/output/keyrings/debian-keyring.gpg --verify *.dsc
+
+Or you can use the following alias:
+
+    dscverify='dscverify --keyring /path/to/debian/keyring/output/keyrings/debian-keyring.gpg'
+
+This assumes that you initialized the `keyring` submodule and compiled the keyrings:
+
+    ( cd keyring && make )
+
+We use `--no-default-keyring` to make sure `gpg` just looks for the key in the `debian-maintainers` keyring.
+
+Another option is to get the specific key:
+
+    gpg --recv-keys 12345678
+
+Either way, you have to have a criteria about how much trust you should give to the keyring or the pubkey 
+you just downloaded. The same goes for software you're porting to Debian and that you can't actually check
+it's signature against `debian-keyring`.
 
 See also:
 
+* `dscverify(1)` manpage.
+* [Debian Public Key Server](http://keyring.debian.org/).
 * [apt get - How to get apt-get source verification working? - Super User](https://superuser.com/questions/626810/how-to-get-apt-get-source-verification-working).
+* [Debian. How can I securely get debian-archive-keyring, so that I can do an apt-get update? NO_PUBKEY - Server Fault](http://serverfault.com/questions/337278/debian-how-can-i-securely-get-debian-archive-keyring-so-that-i-can-do-an-apt-g/337283#337283).
+
+Extracting the source
+---------------------
+
+If needed, do this after your successfully verified the sources:
+
+    dpkg-source -x *.dsc
 
 Getting dependencies
 --------------------