Add Blacklist class

include/Blacklist.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Arionum;
+
+/**
+ * Class Blacklist
+ */
+final class Blacklist
+{
+    /**
+     * The official list of blacklisted public keys
+     */
+    public const PUBLIC_KEYS = [];
+
+    /**
+     * Check if a public key is blacklisted
+     *
+     * @param string $publicKey
+     * @return bool
+     */
+    public static function checkPublicKey(string $publicKey): bool
+    {
+        return key_exists($publicKey, static::PUBLIC_KEYS);
+    }
+}