user11161: Usually I am able to verify signatures using the verify option in GPG, but this doesn't work when attempting to verify the Litecoin Core client DMG.
For example:
$ gpg --verify litecoin-0.14.2-osx.dmg.asc litecoin-0.14.2-osx.dmg
gpg: Signature made Mon Jul 31 14:44:45 2017 PDT
gpg:                using RSA key FE3348877809386C
gpg: Can't check signature: No public key

I am using the GPG 2.2.3 install from Homebrew.

user69718: Here is what I did to get this to work
Copy the public key (found here) to a file. I called it litecoin.public.key.
Then run the following commands:
gpg --import litecoin.public.key
gpg --verify litecoin-0.14.2-osx.dmg.asc litecoin-0.14.2-osx.dmg

This is the output that I got
gpg: Signature made Mon Jul 31 17:44:45 2017 EDT
gpg:                using RSA key FE3348877809386C
gpg: Good signature from "Adrian Gallagher <thrasher@addictionsoftware.com>" [unknown]
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: 59CA F0E9 6F23 F537 4794  5FD4 FE33 4887 7809 386C


11161: <p>Usually I am able to verify signatures using the <code>verify</code> option in GPG, but this doesn't work when attempting to verify the Litecoin Core client DMG.</p>

<p>For example:</p>

<pre><code>$ gpg --verify litecoin-0.14.2-osx.dmg.asc litecoin-0.14.2-osx.dmg
gpg: Signature made Mon Jul 31 14:44:45 2017 PDT
gpg:                using RSA key FE3348877809386C
gpg: Can't check signature: No public key
</code></pre>

<p>I am using the GPG 2.2.3 install from Homebrew.</p>
 69718: <p>Here is what I did to get this to work</p>

<p>Copy the public key (found <a href="https://pgp.mit.edu/pks/lookup?op=get&amp;search=0xFE3348877809386C" rel="nofollow noreferrer">here</a>) to a file. I called it <code>litecoin.public.key</code>.</p>

<p>Then run the following commands:</p>

<pre><code>gpg --import litecoin.public.key
gpg --verify litecoin-0.14.2-osx.dmg.asc litecoin-0.14.2-osx.dmg
</code></pre>

<p>This is the output that I got</p>

<pre><code>gpg: Signature made Mon Jul 31 17:44:45 2017 EDT
gpg:                using RSA key FE3348877809386C
gpg: Good signature from "Adrian Gallagher &lt;thrasher@addictionsoftware.com&gt;" [unknown]
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: 59CA F0E9 6F23 F537 4794  5FD4 FE33 4887 7809 386C
</code></pre>
