Private Keys in a Nutshell

5 min read – Oct 04, 2022

The blockchain has many equally important components; without them, the puzzle wouldn’t be complete. One of them is a Private Key.

Everyone who enters the cryptocurrency space should know the private key’s role and understand how it works.

A Private Key never comes alone and is always created along with a Public Key. The Private Key should always be taken care of with the highest privacy and never shared with others. It constitutes ownership, and losing it, is equivalent to losing the assets. Recreating the private keys is technologically impossible; therefore, good care of them should be your priority.

A Public Key allows receiving the crypto funds (the public addresses derive from it); a Private Key allows sending the funds.

Mnemonic Phrase

Note: We use the term Mnemonic Phrase in this article; however, many other names are in circulation. Some of the common are “Mnemonic Seed”, “Seed Phrase”, “Seed”, “Recovery Words”, or “Recovery Keys” and many more. When you set up the wallet, most likely, you will receive something called a Mnemonic Phrase. A Mnemonic Phrase is a set of 12 to 24 words that is nothing else than a simple representation of a private key. Before mnemonic phrases were introduced (with the BIP39 proposal — BIP stands for Bitcoin Improvement Proposals), private keys for the wallets weren’t so friendly to the end user. Usually, they were provided as long, random alphanumeric characters, hard to remember, and easy to make a very costly error. These words are not just any words taken from the English dictionary; these are 2048 exclusively selected that meet specific criteria. The full list of words you can find here.

For more in detail information about BIP-39 and Mnemonic Phrase proposal, you can find it here

Why is there a difference in the number of words?

The two most common lengths of Private Key in use are 128 and 256 bits. The 256-bit version is considered more secure. At the time of writing, most wallets still operate with 128 bits. The 256-bit Private Key is represented by 24 words, whereas the 128-bit by 12.

Most of the time Private key will be generated for you by the wallet of your choice as a Mnemonic Phrase. You can, however, create the key by yourself. The process of creating the key requires some technical knowledge. You can find many online tutorials about this topic, so we will not cover the details here.

If you want to generate a private key by yourself, you can try by following this article

The same key, different formats

A private key exists in many different formats. The most popular is currently the Mnemonic phrase, but it can also be represented in binary form (ones and zeros), hex (0–9 a-f), and alphanumeric string. Knowing any format is enough to recreate a wallet.

With some technical knowledge, you can convert from one format to another, recreate a Mnemonic Phrase from a long set of ones and zeros, and then the Mnemonic Phrase into a hex or an alphanumeric string.

Can the private key from one wallet work in another?

Each private key is unique to the specific blockchain technology. So, if you have a private key for your Bitcoin created in one wallet, you can easily recover it in a different wallet that supports the Bitcoin blockchain. As a general rule, you can’t use the Private Key from the Bitcoin wallet to enter the wallet that supports Ethereum assets. As much as this sounds obvious to some, this needs to be clear for many.

Note: Some application wallets (i.e., Exodus) use BIP-39 Mnemonic Phrase to create a universal key to access assets across different blockchains.

Using a Mnemonic Phrase directly in the application wallet to recover the assets can be a little bit more complicated. The wallet must support the BIP-39 proposal. Some wallets have custom sets of words or use different technology, and entering your seed may not work. Always check if a wallet is compatible with your Mnemonic Phrase — does the wallet support BIP39? Does the wallet require 12 or 24 words?

How probable is guessing the Private Key?

Guessing any existing private key is nearly impossible. If you want to brute force a particular 128-bit private key, it will take you infinity with all the processing power already in existence.

So how about Mnemonic Phrase? They seem more understandable, so it must be easier to guess, right? No. To guess 12 words, you must know the exact words from the collection of 2048 words and their positions. There is no difference when you try to brute force the private key in the form of 12 words, hex, binary or alphanumeric.

How about Quantum Computers?

Quantum computing is not mainstream, and it looks like it will not be in the near future.

Technology advancement is gradual, never sudden. The adoption of quantum computers will enforce necessary changes on the go; quantum computers will not change the industry over the night. Discussion about quantum resistance blockchain is needed but not critically essential.

Resources

BIP 39 – Mnemonic code for generating deterministic keys

BIP 39 wordlist

How to generate your very own Bitcoin private key