When a government or Internet Service Provider (ISP) blocks access to the Tor network, they typically do so by blocking the IP addresses of the publicly known Tor relay nodes. To circumvent this censorship, the Tor Project developed "bridges." Bridges are Tor relays that are not listed in the main public Tor directory. Because their IP addresses are not public, it is much harder for censors to block all of them. A user in a restricted region can configure their Tor client to connect to the network via a bridge, bypassing the block on public relays and gaining access to the full Tor network.

B. Utilize publicly listed Tor relay nodes: The scenario explicitly states that direct access is restricted, which is accomplished by blocking these publicly known nodes.

C. Establish direct communication with the Tor exit node: This is technically not how the Tor protocol works; connections are routed through a circuit of multiple relays, not directly to an exit node.

D. Collaborate with government authorities: This is contrary to the objective of circumventing government surveillance and censorship.

1. The Tor Project. (n.d.). Tor: Bridges. Official Tor Project Documentation. (The entire page explains that "Bridges are Tor relays that are not listed in the main Tor directory. This means that an ISP or government trying to block access to the Tor network can't simply block all the bridges."). Retrieved from https://tb-manual.torproject.org/bridges/

2. Dingledine

R.

& Mathewson

N. (2006). Tor: The Second-Generation Onion Router. In Proceedings of the 13th USENIX Security Symposium. (While an older source

it lays the foundation for Tor's design. Later work on bridges builds on this to address censorship

as discussed in Section 9

"Resisting censorship and blocking").

3. McCoy

D.

Bauer

K.

Grunwald

D.

Kohno

T.

& Sicker

D. (2008). Shining Light in Dark Places: A Study of Anonymous Network Usage. In Proceedings of the 8th International Conference on Privacy Enhancing Technologies. (This paper discusses censorship of Tor and mentions bridges as a countermeasure

Section 5.1

"Censorship"). DOI: 10.1007/978-3-540-70630-41