Cicada 3301 Puzzle Uses Shamir Algorithm to Distribute Clues 🇺🇸

Original source: Eze Martínez

This video from Eze Martínez covered a lot of ground. Streamed.News selected 8 key moments and summarises them here. Everything below links directly to the timestamp in the original video.

Shamir's Secret Sharing is a fundamental cryptographic solution for protecting sensitive data. Understanding its geometric function reveals how a secret can be divided so no single person possesses it entirely.

Cicada 3301 Puzzle Uses Shamir Algorithm to Distribute Clues

Participants received individual .onion links, each containing identical codes: two numbers, a hyphen, and hexadecimal bytes. This revealed each code as part of a larger message, designed for reconstruction using Shamir's Secret Sharing scheme. Israeli cryptographer Adi Shamir devised the algorithm in 1979. It rebuilds a secret from a minimum number of fragments, geometrically expanding the concept of a one-time pad. This method increased the puzzle's cryptographic complexity and forced decentralized collaboration. No participant could progress alone; several had to share pieces to reveal the next stage. This demonstrated Cicada 3301's aim to filter candidates capable of complex teamwork.

"He geometrically expanded this idea onto a two-coordinate plane. The secret message was a point on the Y-axis, and shared pieces were points on a randomly generated curve."

▶ Watch this segment — 37:10

XOR Operation Reveals 'Gematria Primus,' New Cicada 3301 Key

Faced with a dead end—an MP3 file, hexadecimal tweets, and binary files—the solution emerged from an unexpected cryptographic operation. Applying an XOR, or "exclusive or," between the audio file and tweet strings generated a new binary file. This file proved to be a JPG image. It displayed a table titled 'Gematria Primus,' associating runes, letters, and prime numerical values. Discovering this table provided the next key and highlighted the multidisciplinary knowledge required. The solution demanded lateral thinking to combine disparate files and technical mastery of bit-level operations, effectively filtering out those without deep expertise in computing and cybersecurity.

"When we performed an XOR between the MP3 file and the tweet string, we got another binary file, but notably, this file was an image—a JPG."

▶ Watch this segment — 18:18

Cicada 3301 Moves Puzzle to Real World with Coordinates, Phone Numbers

The next puzzle stage pushed participants beyond the digital realm. An .onion link revealed geographic coordinates. At these physical locations, posters displayed phone numbers. Calling them prompted a code request. Participants used Gematria Primus to decrypt access keys. An automated voice then provided a 'dataset,' an 'offset,' and a hexadecimal 'data' string. Each data set was unique per location. Participants performed an XOR operation with specific puzzle files, revealing a new, individual .onion link for each person. This decentralization heightened logistical complexity and ensured the final puzzle stages remained a confidential, personalized experience, hindering mass collaboration.

"At each of the distinct coordinates, which had different codes, datasets, and offsets, a new onion link formed, not the same one. Each person received their own .onion point, their own page."

▶ Watch this segment — 34:40

Cicada 3301's Final Test: Build TCP Server with Advanced Crypto Commands

After passing a philosophical and technical quiz, participants faced their final challenge: building a functional TCP server. They had to host it as a hidden Tor service and implement eight specific commands, including 'rand' for cryptographically secure pseudorandom numbers, 'quine' for self-replicating code, and 'DH' for Diffie-Hellman key exchange.

This task served as the ultimate filter, shifting from puzzle-solving to applied software engineering. Requiring complex concepts like base-29 numbering or 'quines' showed Cicada 3301 sought not just bright minds, but programmers with deep, practical mastery of theoretical computer science and cryptography.

"In your preferred programming language, build a TCP server that implements the protocol below. You, and only you, must write the server code."

▶ Watch this segment — 45:23

How 'Onion Routing' Ensures Anonymity on Tor Network

Cicada 3301's ".onion" links are only accessible via the Tor network, which uses 'onion routing' for anonymous communication. Before sending a message, it's encrypted in multiple layers, like an onion, with different keys. Each intermediate network node can decrypt only one layer to find the next hop. It cannot see the origin, final destination, or full message content.

This multilayer encryption makes communication virtually untraceable, protecting sender and receiver identities. Cicada 3301's choice of this technology highlights its focus on confidentiality and privacy, also filtering for participants with digital security knowledge.

"It's like peeling onion layers, hence 'onion.' This way, anyone intercepting communication can't know who sent it, who receives it, or the message content."

▶ Watch this segment — 24:40

Cicada 3301 Hides Next Clue in 'Ping' Response Packets

A new cryptic clue, "sometimes one needs to strike the sky and listen to the sound," network-savvy participants interpreted as an instruction to 'ping' the puzzle's .onion address. While 'ping' verifies connectivity and its response packets usually carry irrelevant data, Cicada 3301 had modified its server to conceal information within them.

Deciphering the message required a protocol analyzer like Wireshark to intercept and examine the 32-byte packet content. By reassembling the hidden data, participants revealed a new PGP-signed message, directing them to the next dark web link. This once again showcased the puzzle creators' technical brilliance.

"3301 configured the server for these packets to contain information. Brilliant. Never thought of that."

▶ Watch this segment — 32:39

Gematria Primus, Steganography Reveal Cicada 3301's First Dark Web Link

Participants confirmed the Gematria Primus table's utility. Summing numerical values for letters in an MP3 song title yielded 761, the file name. Analyzing the Gematria Primus image with Outguess, a steganography tool, revealed a hidden, PGP-signed message. It contained no visible text, only tabs and spaces.

With just two elements, participants inferred a binary system. They assigned zeros to spaces, ones to tabs, then converted the sequence to binary and finally ASCII text. This yielded the next clue: the first .onion dark web link, marking a new level of puzzle secrecy.

"Given only two elements in the message—tabs and spaces—we can infer a binary system."

▶ Watch this segment — 22:59

Dark Web Server Challenges Players with Prime Number Commands

Participants accessed the first .onion link via Telnet, a text-based network protocol, finding an interactive server. The program responded to specific commands: it could factor numbers or, if prime, invert them. A 'primes' command listed prime numbers up to 3301, but with unusual gaps and spacing, suggesting a hidden pattern.

The server also used Gematria Primus via a 'count' command to analyze phrases and find 'reversible primes.' Combining these numerical clues with a hidden message obtained by sending a word in hexadecimal format, finally revealed a second .onion link. This showed the solution required both mathematical analysis and methodical interface exploration.

"If we typed 'primes,' the server responded with all prime numbers up to 3301, but with two small details."

▶ Watch this segment — 27:13

Summarised from Eze Martínez · 54:05. All credit belongs to the original creators. Streamed.News summarises publicly available video content.