[WIP] Add guide to setup GPG commit verification

content/en/docs/guides/commit-signature-verification.md

@@ -0,0 +1,70 @@
+---
+title: "Setup GPG commit verification"
+linkTitle: "Setup GPG commit verification"
+description: "Configure GPG commit verification to add another layer of security in case of compromised GitOps repository"
+weight: 100
+---
+
+You may want to add another layer of security in case your GitOps repository is compromised.  
+With commit signature verification, commits must be [signed](https://git-scm.com/book/en/v2/Git-Tools-Signing-Your-Work) using an authorized GPG key to be applied to the cluster.
+
+## Prerequisites
+
+To follow this guide you'll need a Kubernetes cluster with the GitOps 
+toolkit controllers installed on it.
+Please see the [get started guide](../get-started/index.md)
+or the [installation guide](../installation/).
+
+## Import your GPG public keys as Secret
+
+In order to verify commit signatures, the source controller needs to have GPG **public** keys.
+
+Create a `flux-gpg-pubkeys` secret:
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: flux-gpg-pubkeys
+  namespace: flux-system
+data:
+  my_key.asc: <YOUR KEY IN BASE64>
+```
+Note: You can add multiple keys
+
+Your GPG key may be exported as one-line base64 string using:
+
+```sh
+gpg --armor --export <KEY_ID> | base64 -w 0
+```
+
+## Configure GOTK to verify commit signature
+
+You have to [customize flux manifests](../installation/#customize-flux-manifests) to enable signature verification.
+
+Create a patch as `gpg-commit-verification.yaml` in `flux-system` directory:
+
+```yaml
+apiVersion: source.toolkit.fluxcd.io/v1beta1
+kind: GitRepository
+metadata:
+  name: flux-system
+  namespace: flux-system
+spec:
+  verify:
+    mode: head
+    secretRef:
+      name: flux-gpg-pubkeys
+```
+
+Include this patch using `patchesStrategicMerge` in `kustomization.yaml`:
+
+```yaml
+patchesStrategicMerge:
+- gpg-commit-verification.yaml
+```
+
+Commit and push your changes.
+
+Future commits must now be signed.  
+If a commit is not signed, it will not be applied to the cluster (an error will be showed in source controller logs)