Metal backups for your Bitcoin

Wallets and security

Use a metal recovery seed to protect your assets for the long term

One of the most mind-bending properties of Bitcoin is that with just 12 words any amount of wealth can be kept safe, under the control of a single person.

Your recovery seed is a list of words that backs up your Bitcoin keys. It must be stored in physical form written down as a list of words and hiding them somewhere, safe from online and physical attack. While you can also memorize your recovery seed, you should never rely on memory alone.

So how do you take care of a recovery seed?

Why use a metal backup?

As long as your keys were generated offline by your Trezor hardware wallet, they are unique. To ensure long-term access to your Bitcoin, you need to back them up offline and keep them as safe as possible.

All our wallets come with paper templates that you can use to write down your recovery seed. Paper and pencil is surprisingly resilient and takes a long time to degrade, but it is vulnerable to fire, water and other environmental factors. To prevent disaster, you should consider eventually upgrading to a metal recovery seed.

What stands the test of time longer than paper? Metal. Since the creation of the BIP39 recovery seed standard, dozens of companies have been creating plates, capsules and other products which are purpose-built to store seed words.

Metal backups come in many shapes and sizes, but are most commonly made of stainless steel or titanium; metals which can withstand housefires, munitions impact, corrosion and more.

An overview of metal recovery seeds

While almost all available options will be more resilient than a paper backup, there are significant differences between products.

Different materials will tolerate different environments; the shape of the backup will mean some are easier to hide; and the design will mean some are more prone to data loss if damaged, but they may also easier to use than others depending on whether they record full words or just abbreviations.

All of this should be considered according to your personal security needs. Jameson Lopp’s Bitcoin resources include methodical documentation of extreme tests of 70 metal backups that are highly recommended reading when deciding which backup is right for you.

Metal Bitcoin Seed Storage Reviews

What metal seed backup to buy

At Trezor, we offer several tried-and-tested metal backup solutions from renowned companies with a long track-record of customer satisfaction. Depending on what type of recovery seed you have and how you want to store it, certain products may be more suitable than others. Take a look at the options and see what product best suits your use-case.

Standard recovery seed (one 12-word or 24-word list)

If you use a Model One, the standard recovery seed is a single list of 24 words, while the Model T creates one list of 12 words by default. To keep a recovery seed safe, you need to store it as a single list, in order.

Almost all metal backup products can accommodate up to 24-words of data, though they may be abbreviated. The choice is therefore up to you, and will depend on how you plan to store your seed and how easy you want it to be to recover the data.

A standard recovery seed poses a single point of failure, so it is important to choose a backup that will withstand the maximum amount of damage and remain legible.

Recommended solutions:

• CryptoTag Zeus

Trezor Hardware Wallet Accessories | Cryptotag Zeus

Made of titanium, this backup solution was awarded the highest marks across all factors tested in Lopp’s stress tests. With a decade in the industry, CryptoTag are one of the leading brands for metal backup solutions. Data is punched as numbers, corresponding to the word’s position on the BIP39 wordlist.

• Cryptosteel cassette

Trezor Hardware Wallet Accessories | Cryptosteel Cassette

Cryptosteel’s tile-based solution provides protection from fire and corrosion but is less resistant to crushing. At a lower price point than the CryptoTag, the Cassette is a great pick for anyone storing their seed in a durable spot such as a reinforced safe, where the plate is unlikely to be deformed.

Data is stored using small metal tiles, making it easy to recover but less resilient.

Shamir backup (multiple 20-word shares)

For more resilience against data loss, a Shamir backup is recommended over the standard seed. Shamir backup is only available on the Trezor Model T, and lets you choose how many shares to create and how many need to be used to recover the wallet.

What is Shamir backup?

You can have 3, 5, or as many as 16 separate lists to protect. Not all the shares need to survive to restore your wallet, but it is a good idea to keep at least the threshold required to restore the wallet safe in metal.

While the above products can also be used for Shamir backup, you will need one for each list, so a more economical solution is the Cryptosteel capsule. These are thin metal cylinders that hold letter tiles and can store 123 characters of data each. Buying multiple capsules will save you money, so you can safely protect all of your Shamir shares for the long term.

While these capsules only received a B grade for crushing from Lopp’s tests, they received an overall A-, which will be sufficient in most cases since Shamir allows several shares to be sacrificed without losing access to your funds.

Recommended solution:

• Cryptosteel Capsule Duo

Trezor Hardware Wallet Accessories | Cryptosteel Capsule Duo

Sold in pairs of two or on their own, these metal time capsules are portable and discreet, giving you plenty of hiding places to choose from. Combine multiple capsules to match the number of Shamir shares you have, and then distribute them across different locations, giving each share the best chance of survival for the long term.

Data is stored on metal tiles threaded inside the cylinder.

Metal backups for your Bitcoin was originally published in Trezor Blog on Medium, where people are continuing the conversation by highlighting and responding to this story.