TokenGen CreateTokenHash from array of strings.

API/TokenGen.cs

@@ -1,4 +1,5 @@
 using System.Security.Cryptography;
+using System.Text;
 
 namespace API;
 
@@ -20,4 +21,20 @@ public static class TokenGen
         key = string.Join('-', prefix, key);
         return key;
     }
+
+    public static string CreateTokenHash(string prefix, uint fullLength, string[] keys)
+    {
+        if (prefix.Length + 1 >= fullLength - MinimumLength)
+            throw new ArgumentException("Prefix to long to create Token of meaningful length.");
+        int l = (int)(fullLength - prefix.Length - 1);
+        MD5 md5 = MD5.Create();
+        byte[][] hashes = keys.Select(key => md5.ComputeHash(Encoding.UTF8.GetBytes(key))).ToArray();
+        byte[] xOrHash = new byte[l];
+        foreach (byte[] hash in hashes)
+            for(int i = 0; i < hash.Length; i++)
+                xOrHash[i] = (byte)(xOrHash[i] ^ (i >= hash.Length ? 0 : hash[i]));
+        string key = new (xOrHash.Select(b => Chars[b % Chars.Length]).ToArray());
+        key = string.Join('-', prefix, key);
+        return key;
+    }
 }