update sigs and testing instructions for 16.04.6.4

Author: dougburks

checksums.txt

@@ -1,3 +1,8 @@
+16.04.6.4 ISO image
+md5sum 8b5b60570e76bc4999c365ed6a01ea80
+sha1sum 4b4836ffde205e114031c9e8e4b22ccbb45ef065
+sha256sum 4e452ef624306551c6aa1858d838db864be6253b45285f4bfb842c666d4dc2e1
+
 16.04.6.3 ISO image
 md5sum d24b22a4549ac572a20167c988cc2ce9
 sha1sum 04f8980208edcf4f4b02b2463a4fe0ad25eb0778

sigs/securityonion-16.04.6.4.iso.sig

@@ -0,0 +1,51 @@
+### 16.04.6.4 ISO image built on 2020/02/06
+
+### Download and Verify
+
+16.04.6.4 ISO image:  
+https://github.com/Security-Onion-Solutions/security-onion/releases/download/v16.04.6.4_20200206/securityonion-16.04.6.4.iso
+
+Signature for ISO image:  
+https://github.com/Security-Onion-Solutions/security-onion/raw/master/sigs/securityonion-16.04.6.4.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-16.04.6.4.iso.sig
+```
+
+Download the ISO image:  
+```
+wget https://github.com/Security-Onion-Solutions/security-onion/releases/download/v16.04.6.4_20200206/securityonion-16.04.6.4.iso
+```
+
+Verify the downloaded ISO image using the signature file:  
+```
+gpg --verify securityonion-16.04.6.4.iso.sig securityonion-16.04.6.4.iso
+```
+
+The output should show "Good signature" and the Primary key fingerprint should match what's shown below:
+```
+gpg: Signature made Fri 07 Feb 2020 08:34:39 AM EST using RSA key ID ED6CF680
+gpg: Good signature from "Doug Burks <doug.burks@gmail.com>"
+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://securityonion.net/docs/Installation