What is Time-Lock Cryptography?

A Time-Lock Puzzle is a cryptographic method that mathematically guarantees that no one — not even the sender — can decrypt before a predetermined time. Designed to "send information into the future," it was proposed in 1996 by Ron Rivest, Adi Shamir, and David Wagner — two of whom co-invented RSA encryption.

A complex puzzle that takes time even on cutting-edge hardware is generated on the spot. The puzzle's answer becomes the key, and your link or file is completely locked behind it.

How it works

The puzzle is a simple repeated squaring: square x, divide by a large number N, take the remainder, square again, divide by N… Repeating this tens of thousands to hundreds of millions of times creates an arbitrary computational load, making the unlock time fully adjustable.

Why can't it be skipped?

Normally you speed up computation by parallelizing across multiple cores or machines — but that does not work here.

Looking at the formula, each step takes the previous step's output as input. Without knowing the prior answer, the next step cannot begin — making parallel computation impossible.

As a result, decryption time depends solely on the CPU's single-thread performance and the configured number of iterations.

How Brake. implements it

When Brake. receives an encryption request, it first generates a random base x₀ and two large primes p, q. A sequential-squaring puzzle (the time key) is created modulo N = p × q, and your file is locked with it. The number of iterations is calculated from the requested unlock time.

The entire encryption process runs in your browser (JavaScript BigInt). Only the encrypted data and puzzle parameters are sent to the server — your content and keys never leave your device. Even in the event of a server breach, the file contents cannot be exposed.

When decryption begins, all computation runs on the recipient's own device (PC or smartphone).