DEFIANCE's Address-Change Signaling (ACS) requires each client to contact a sequence of IP addresses with precise timing (per-user wait and window parameters) and a one-time passphrase derived from NET provisioning. Connections arriving out of order, outside the timing window, or lacking the correct passphrase receive only innocuous content, so a censor probing a suspected address block finds only normal commodity servers.

A balls-and-bins analysis shows that an adversary conducting N full rounds of a rate-limited rendezvous protocol discovers only 63% of a pool of N entry points; full coverage requires N ln N rounds (the coupon collector's bound). Concretely, with three 8-hour shifts of 100 humans performing 60-minute CAPTCHA+proof-of-work challenges, an adversary discovers ~2,400 entry points per day, exhausting a static pool of 10,000 addresses in roughly 19 days.

§3 evaluation

The Chinese Great Firewall was observed conducting two follow-up probes for each outbound TCP/443 connection: the first with garbage binary data (target unknown) and the second specifically performing an SSL negotiation, an SSL renegotiation, and successfully building a one-hop Tor circuit to confirm the bridge. This reactive probing renders unpublished Tor entry points discoverable even when not listed in any directory.

§1 detection

NET payloads are wrapped in three nested layers — (1) steganographic encoding plus transport encryption with a factory digital signature, (2) proof-of-life (CAPTCHA), and (3) proof-of-work (computational puzzle) — so that even an adversary who harvests many payloads cannot decode them faster than gateway addresses can be rotated. The payload format is explicitly extensible to add harder challenges as adversaries improve.

§3.3 defense

The mod_freedom Apache module hooks into the HTTP 404 ErrorDocument handler and steganographically embeds encrypted NET payloads in image responses to valid RP requests, while returning normal content to all other clients. Using Identity-Based Encryption (IBE, Boneh-Franklin) keyed on the server's hostname eliminates any need for out-of-band public-key distribution and allows deployment on thousands of volunteer webservers without mutual trust.

§3.1 defense

CensorLess's function refresher automatically retires serverless bridges and deploys fresh ones in batches across diverse regions; the expected time until a bridge is identified and blocked in practice is 2 days (per Fifield et al.), while Tor bridges in China are discovered within 2–36 days. The old bridge is only removed after all clients have completed live migration to a new URL, maintaining uninterrupted connectivity.

2026-kang-censorless-serverless §4.5 active-probingip-blocking

CensorLess's threat model explicitly relies on a rational-censor assumption: the censor will not block entire cloud-provider IP ranges or domain namespaces because the collateral damage to legitimate business services would be politically and economically unacceptable. AWS Lambda's inherent IP-address ephemerality (new IPs on each invocation, function lifetime up to 15 minutes) means even censors willing to attempt enumeration face a continuously shifting target distributed across the cloud provider's global address space.

2026-kang-censorless-serverless §4.2 ip-blockingasn-blackholingactive-probing

Address blocking is a losing strategy for the censor: with n=8 endpoints and µ/λa = 1 (discovery as fast as rotation), address-denial probability falls below 10^-2, and even when the censor discovers twice as fast as the defender rotates (µ/λa = 0.5), 7 endpoints keep address denial below 10^-2 (Lemma 1, Figure 1). The collateral budget γ means the censor cannot even block all addresses it discovers, and Corollary 1 gives the explicit threshold: n ≥ ln(1/ε) / ln((λa+µ)/λa) endpoints suffice for any target ε.

2026-maiti-block-a-mole-sustainability-frontier §5, §8.1, §8.10, Lemma 1, Corollary 1, Figure 1 ip-blockingactive-probing

Community members propose a two-hop architecture as a potential mitigation for Iran's current DPI upgrade: a first-hop server inside Iran's whitelisted datacenter ranges (where outbound traffic faces lighter inspection) proxying to a foreign exit node, with Reality masquerading as a legitimate Iranian organization's domain. The architecture's effectiveness under active TCP reassembly and handshake probing is explicitly unverified.

2026-pooribitwise-iran-advanced-dpi Issue body — Description active-probingip-blocking

A community scan of the I2P network database (netDb) in July 2026 identified a cluster of suspicious router nodes uniformly running I2P version 0.9.66 (three versions behind the current 0.9.69), all hosted in Chinese domestic data centers rather than residential broadband. The nodes exhibit anomalous uniformity in their router capabilities (Caps) configuration and self-reported versions, a pattern inconsistent with organic user deployments.

2026-thewizard0fbsod-quirky-chinese-i2p Issue body active-probingip-blocking

The suspicious Chinese I2P nodes rotate their IP addresses regularly and simultaneously as a coordinated group, and some of the observed IPs have prior history of malicious behavior (SSH brute-forcing, remote exploitation) in threat-intelligence databases. Simultaneous coordinated IP rotation distinguishes state-run infrastructure from organic users and is a fingerprint of centrally managed probe fleets.

2026-thewizard0fbsod-quirky-chinese-i2p Issue body active-probingip-blocking