2.3 Alternative Darknets:

While Tor is the most well-known anonymity network, it represents only one model of hidden network architecture.
Other darknets — I2P, Freenet, GNUnet, Yggdrasil, and Nym — use fundamentally different routing designs, anonymity concepts, and security assumptions.

This chapter explains the underlying mechanisms that make each network unique.

A. I2P (Invisible Internet Project) — Tunnels & Garlic Routing

I2P is a self-contained darknet focusing on internal anonymous services rather than clearnet access.
Its architecture relies on a tunnel-based routing system and a unique encryption approach called garlic routing.

1. I2P Unidirectional Tunnels

Unlike Tor, where traffic flows bidirectionally over a single circuit, I2P builds two independent tunnels:

Inbound Tunnel: carries data toward the user
Outbound Tunnel: carries data away from the user

Benefits

Breaks correlation between incoming and outgoing traffic
Limits the impact of a compromised router
Provides flexibility for performance tuning

Each tunnel is a series of routers that forward encrypted packets.

2. Garlic Routing (I2P’s Encryption Model)

Garlic routing extends onion routing by bundling multiple messages (“cloves”) into a single encrypted “garlic bulb.”

Advantages

Anti-traffic-analysis: harder to isolate individual messages.
Message aggregation: routing instructions and payloads can be packaged together.
Decoy traffic: supports padding and nested messaging.

Garlic routing is considered more flexible than onion routing for peer-to-peer anonymity.

3. I2P Network Database (netDB)

I2P uses a distributed hash table (DHT) to store:

router information
tunnel build records
encrypted destination entries

This ensures:

decentralization
resilience
no directory authorities (unlike Tor)

B. Freenet — Distributed Data Store & “Insert/Fetch” Mechanism

Freenet is not a routing network like Tor or I2P.
It is a distributed, censorship-resistant storage system built around a key-based data retrieval model.

1. Key-Based Data Access

Freenet uses three key types:

CHK (Content Hash Key): ensures immutability
SSK (Signed Subspace Key): allows updatable content
USK (Updatable Subspace Key): supports pseudonymous updates

Data is retrieved by keys, not by location.

2. Data Insert / Data Fetch Model

Insert

User uploads data using a key.
Chunks split and distributed across nodes.
Replication occurs automatically.

Fetch

User requests a key.
Network routes request through probabilistic local decisions.

This ensures censorship-resistance and plausible deniability.

3. Location-Independent Storage

Users do not know:

where the data is stored
who stores it
how many copies exist

Nodes store encrypted chunks, making Freenet:

anonymous
fault-tolerant
self-healing

C. GNUnet — Peer Group Cryptography & Privacy-Preserving Naming

GNUnet is a framework for privacy-preserving, decentralized networking.
It emphasizes secure group communication, peer authentication, and anonymous services.

1. Peer Group Cryptography

GNUnet forms “peer groups” where nodes authenticate using:

public key infrastructure
secure channel establishment
routing within trusted peer subsets

This balances anonymity with authenticity.

2. GNU Name System (GNS)

Unlike DNS, GNS provides:

decentralized name resolution
censorship resistance
privacy-preserving queries

Names are derived from:

zones
public keys
delegation chains

This system avoids centralized control by ICANN or DNS root authorities.

3. Transport Plugins

GNUnet can run over:

TCP
UDP
HTTP tunnels
Bluetooth
WLAN

This flexibility allows it to survive censorship conditions where Tor or I2P may fail.

D. Yggdrasil — DHT-Based Global IPv6 Mesh

Yggdrasil is not a classical anonymity network — it is a cryptographically secure global mesh networking overlay that automatically assigns IPv6 addresses.

1. Public-Key-Based Addressing

Each node’s IPv6 address is derived from:

its cryptographic key
routing tree position

This ensures:

end-to-end encryption
secure cryptographic identity

2. Distributed Hash Table Routing

Nodes connect through a spanning-tree-based DHT.

Properties

efficient global pathfinding
dynamic rebalancing
robust connectivity

3. Purpose

Yggdrasil focuses on:

encrypted connectivity
decentralized internet infrastructure
mesh-based peer routing

It offers privacy, but not the anonymity guarantees of Tor or Nym.

E. Nym Mixnet — Layered Privacy & Metadata Resistance

Nym modernizes Chaumian mix networks for the contemporary internet age.

1. Mix Nodes Perform Batch-and-Shuffle

Each node:

collects packets
adds timing delays
shuffles order
forwards output

This destroys metadata such as:

timing
packet size
order

Mixnets are designed to resist global passive adversaries, something onion routing struggles with.

2. Sphinx Packet Format

Sphinx provides:

compact onion-style wrapping
replay protection
unlinkable routing
reduced overhead

Originally a theoretical design, now used in production (Nym, Loopix).

3. Layered Architecture

Nym architecture includes:

Gateway Layer — mixes ingress traffic
Mixnet Layer — multi-hop mixing for anonymity
Credential Layer — privacy-preserving authentication (ZK proofs)
Blockchain Layer — decentralized incentive system

It offers some of the strongest metadata protection available today.