update sigs and testing instructions for 14.04.5.3

Author: dougburks

checksums.txt

@@ -1,3 +1,8 @@
+14.04.5.3 ISO image
+md5sum fb80ccb2d3c0f3f511823fa5858f87d1
+sha1sum 469135cb005e09a59bcc2122962b1b69bfcbceee
+sha256sum 357e67be43b99f2727a8b53aa2a82ed034dfca2658e675d7816b853c42d0ac79
+
 14.04.5.2 ISO image
 md5sum cd32bbbeffc1e4e26b8549a6cfd3f597
 sha1sum a00e0c6cea2d80ea440a92edeed3a206703ba6bb

sigs/securityonion-14.04.5.3.iso.sig

@@ -0,0 +1,47 @@
+ISO image:  
+https://github.com/Security-Onion-Solutions/security-onion/releases/download/v14.04.5.3/securityonion-14.04.5.3.iso
+
+Signature for ISO image:  
+https://github.com/Security-Onion-Solutions/security-onion/raw/master/sigs/securityonion-14.04.5.3.iso.sig  
+
+Signing key:  
+https://raw.githubusercontent.com/Security-Onion-Solutions/security-onion/master/KEYS  
+
+For example, here are the steps you can use on most Linux distributions to download and verify our Security Onion ISO image.
+
+Download the signing key:  
+```
+wget https://raw.githubusercontent.com/Security-Onion-Solutions/security-onion/master/KEYS
+```
+
+Import the signing key:  
+```
+gpg --import KEYS
+```
+
+Download the signature file for the ISO:  
+```
+wget https://github.com/Security-Onion-Solutions/security-onion/raw/master/sigs/securityonion-14.04.5.3.iso.sig
+```
+
+Download the ISO image:  
+```
+wget https://github.com/Security-Onion-Solutions/security-onion/releases/download/v14.04.5.3/securityonion-14.04.5.3.iso
+```
+
+Verify the downloaded ISO image using the signature file:  
+```
+gpg --verify securityonion-14.04.5.3.iso.sig securityonion-14.04.5.3.iso
+```
+
+The output should show "Good signature" and the Primary key fingerprint should match what's shown below:
+```
+gpg: Signature made Wed 06 Sep 2017 08:09:04 AM EDT using RSA key ID ED6CF680
+gpg: Good signature from "Doug Burks <[email protected]>"
+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: BD56 2813 E345 A068 5FBB  91D3 788F 62F8 ED6C F680
+```
+
+Once you've verified the ISO image, you're ready to proceed to our Installation guide:  
+https://github.com/Security-Onion-Solutions/security-onion/wiki/Installation