title: How to verify downloaded file with .sig file?
body: <p>When I download GCC, it also has a <code>.sig</code> file, and I think it is provided to verify downloaded file.
  (I downloaded GCC from <a href="http://ftp.kaist.ac.kr/gnu/gnu/gcc/gcc-4.7.2/">here</a>).</p>
  
  <p>But I can't figure out how should I use it. I tried <code>gpg</code>, but it complains about public key.</p>
  
  <pre><code>[root@localhost src]# gpg --verify gcc-4.7.2.tar.gz.sig gcc-4.7.2.tar.gz
  gpg: Signature made Thu 20 Sep 2012 07:30:44 PM KST using DSA key ID C3C45C06
  gpg: Can't check signature: No public key
  [root@localhost src]# 
  </code></pre>
  
  <p>How can I verify downloaded file with <code>.sig</code> file?</p>