Hostname Cloaking

Cloaking Block

cloaking: [
  enabled: true,
  cloak_keys: [
    "SecretKey1Random30PlusCharactersGoesHere!!",
    "SecretKey2Random30PlusCharactersGoesHere!!",
    "SecretKey3Random30PlusCharactersGoesHere!!"
  ],
  cloak_prefix: "elixir",
  cloak_on_connect: false,
  cloak_allow_disable: true,
  cloak_domain_parts: 2
]

Options

Option	Default	Description
enabled	true	Enable hostname cloaking feature
cloak_keys	(example keys)	Secret keys for HMAC-based cloaking
cloak_prefix	"elixir"	Prefix for cloaked hostnames
cloak_on_connect	false	Auto-enable +x when users connect
cloak_allow_disable	true	Allow users to remove +x mode
cloak_domain_parts	2	Number of domain segments to preserve

How Cloaking Works

Hostname cloaking replaces a user’s real hostname with a deterministic but opaque hash. The algorithm:

1. Takes the user’s real IP address and resolved hostname
2. Computes an HMAC hash using the configured cloak_keys
3. Produces a hostname like: elixir-A3F2B1C8.isp.com

The hash is deterministic — the same real hostname always produces the same cloak. This means:

• Bans on cloaked hostnames still work (same user = same cloak)
• But different users from the same ISP get different cloaks (based on their specific address)

Cloak Keys

The keys must be:

• At least 3 keys (for rotation capability)
• At least 30 characters each
• Kept secret — anyone with these keys can reverse-engineer which real addresses map to which cloaks

To generate secure keys:

# In iex or docker exec remote shell
:crypto.strong_rand_bytes(32) |> Base.encode64()

Run this command 3 times to get 3 unique keys.

Key rotation: You can add new keys and remove old ones without breaking existing bans, because the system uses multiple keys and bans match against any of them.

Cloak Examples

With cloak_prefix: "elixir" and cloak_domain_parts: 2:

Real hostname	Cloaked hostname
192.168.1.100	elixir-A3F2B1C8.home.example.com
user.isp.net	elixir-B7D3F1A2.isp.net
2001:db8::1	elixir-C9E5A7D1.ipv6.example.org

The last cloak_domain_parts segments of the original hostname are preserved.

Auto-Cloaking on Connect

If cloak_on_connect: true, users automatically get the +x (Cloaked) mode during the connection handshake. This means their hostname is cloaked before they join any channels.

Preventing Disabling

If cloak_allow_disable: false, users cannot remove their +x mode — their hostname is always cloaked. This is useful on privacy-focused networks.

See also Hostname Cloaking (Security) for the user-facing perspective.