Comment 4 for bug 731931

I just tried to build the libtiff package from source with the following to get the packages needed:

sudo apt-get build-dep tiff
apt-get source tiff

This has some errors on verifying:

Reading package lists... Done
Building dependency tree
Reading state information... Done
Need to get 1,442kB of source archives.
Get: 1 http://gb.archive.ubuntu.com/ubuntu/ lucid-updates/main tiff 3.9.2-2ubuntu0.4 (dsc) [1,936B]
Get: 2 http://gb.archive.ubuntu.com/ubuntu/ lucid-updates/main tiff 3.9.2-2ubuntu0.4 (tar) [1,420kB]
Get: 3 http://gb.archive.ubuntu.com/ubuntu/ lucid-updates/main tiff 3.9.2-2ubuntu0.4 (diff) [20.1kB]
Fetched 1,442kB in 1s (836kB/s)
gpgv: Signature made Fri 04 Mar 2011 15:32:38 GMT using RSA key ID A744BE93
gpgv: Can't check signature: public key not found
dpkg-source: warning: failed to verify signature on ./tiff_3.9.2-2ubuntu0.4.dsc
dpkg-source: info: extracting tiff in tiff-3.9.2
dpkg-source: info: unpacking tiff_3.9.2.orig.tar.gz
dpkg-source: info: applying tiff_3.9.2-2ubuntu0.4.diff.gz

Which organisations public key is missing?

But more importantly I don't see the line mentioned above in the source tif_fax3.h, where as I do see it mentioned in the patch tiff_3.9.2-2ubuntu0.4.diff

Why is it not being applied here, as it said it did in the last line?