The Security of mnemonic phrases, a race against time and computational power

Lately, I’ve been diving deep into the mechanics of how mnemonic phrases actually protect digital assets, and I’ve come to a realization that feels fascinating and unsettling, the entire security model of a mnemonic is nothing more than a bet against time and computing power.

🔹 The Foundation of Mnemonic Security

A 12–24 word mnemonic phrase is not inherently “secure” because of some magical encryption; it’s secure because we don’t have enough computing power or time to test every possible combination in a reasonable window.

Each word in a mnemonic represents 11 bits of entropy, and a 24-word mnemonic carries 256 bits in total. That’s so astronomically large that even with every supercomputer combined, you wouldn’t scratch the surface in millions of years, with today’s computing limits.

🔹 Security Through Delay

I like to call this concept “security through delay.”
It’s the idea that the only thing stopping someone from brute forcing a mnemonic is the delay imposed by computation time.

Once that barrier falls, due to advancements in distributed systems, GPU parallelization, or quantum computing, the walls protecting mnemonic-based wallets thin drastically.

🔹 My Experiment: Simulating Mnemonic Testing

Out of curiosity (and for educational purposes), I wrote a Node.js script that can generate random mnemonic combinations and validate them against checksum patterns and also iterate possible phrases with as little as one word know with exact position amongst the 12/24 words essentially simulating what a brute-force attempt would look like in a constrained environment.

The code doesn’t hack anything — it just explores how wallets derive from mnemonic entropy and how computationally expensive it is to validate each phrase through checksum rules.

Here’s what I learned from the process:

1. Even one missing word multiplies the time cost exponentially. Recovering a 24-word mnemonic with even 1 unknown word is computationally monstrous.

2. Checksum validation narrows the space, but not enough to be practical.
The checksum eliminates invalid combinations, but not nearly enough to make brute-forcing viable.

3. Parallelization helps, but only marginally.
Even when distributing across threads or GPUs, time remains the ultimate limiting factor.

This experiment made clear, the safety of your mnemonic phrase doesn’t lie in a secret algorithm, it lies in the absence of sufficient computing power to test all possibilities within your lifetime.

Until the balance between entropy and computation shifts, time remains the unsung guardian of our digital wealth.