In brief

  • Hardware wallets are often considered the gold standard in cryptocurrency security.
  • For extra peace of mind, you can use a a secure seed storage solution such as a metal wallet.
  • We take a look at some of the most popular options on the market.
  • UPDATED 21 May 2020

When it comes to safely storing cryptocurrencies, hardware wallets are generally considered to be the gold standard for secure storage and accessibility.

Although cold storage devices like the Ledger Nano X and Cobo Vault are certainly a secure way to store digital assets, ultimately they're only as secure as the seed phrase they use to access and manage these assets. This seed phrase is usually a 12 to 24-word phrase that can be used to generate all of the addresses and private keys associated with a wallet when recovered. Most hardware wallets ship with a card that can be used to record this seed phrase, but this can be damaged or lost, making it impossible to recover the wallet.

That's where metal wallets and other more robust seed storage kits come in. They're used to protect seed phrases, private keys, and other sensitive information against damage, ensuring it remains intact even under extreme conditions. Like hardware wallets, there are now a huge variety of different seed storage solutions on the market, each of which promises to keep your seed phrase protected against myriad threats, such as natural disasters and fires.

We've rounded up some of the best seed storage options on the market for our review.

CryptoSteel Capsule

The CryptoSteel Capsule can store up to 123 characters of information (Image: Decrypt)

If there is one name that's practically synonymous with the term "metal wallet," it's CryptoSteel. Billed as the "mother of all backups", the CryptoSteel Capsule is an incredibly secure offline storage solution for cryptocurrency private keys, mnemonic phrases, passwords and practically anything else that can be expressed with uppercase and lowercase letters, as well as symbols and spaces.

The CryptoSteel Capsule is rated fireproof up to 1400°C/2500°F, completely waterproof, and can resist extreme crushing and shocks. The unit measures in at 102 mm in length and 16 mm in diameter, making it both portable and inconspicuous.

The capsule comprises a hollow shell with an internal core—or rail—which is used to hold individual tiles, each of which is engraved with a single letter or symbol. These tiles are placed onto the rail in the correct sequence and are secured with a fastener—this simply prevents the tiles from falling off the core, ensuring they stay in their correct order. The CryptoSteel Capsule can store up to 123 characters of information, sufficient to hold an entire 12-word recovery seed or an abbreviated 24-word one.

As its name suggests, the CryptoSteel Capsule is a capsule-like metal wallet that is constructed out of two types of stainless steel. The outer shell is made from 303-grade stainless steel, which offers extreme strength and defense against water, fire and pressure, and doesn't deform with time, whereas the core is made 304-grade stainless steel, which also offers excellent strength, as well as corrosion and heat resistance. The tiles, fasteners, and separators are made from the same 304-grade stainless steel.
The CryptoSteel capsule is available from the official store for €89, but sets of two or more capsules can be purchased for a discount.

Our Verdict: 4.5/5

If you have the budget for it, the CryptoSteel capsule is easily one of the most versatile and secure offline secret storage solutions available.

cryptosteel.com

Crypto Key Stack

The Crypto Key Stack is ideal for holding multiple BIP39 recovery seeds (Image: Decrypt)

The Crypto Key Stack is a popular mnemonic seed storage solution that's designed to resist a range of physical threats without compromising data.

Like many metal wallets, the Crypto Key Stack takes the form of a set of metal plates—black anodized stainless steel, in this case—stacked together and held in place with a screw. These plates come in two types: the first is engraved with the numbers 1 to 24, with a space for etching a mnemonic word next to it; whereas the second type is blank, used for covering the engraving plates or inscribing generic data.

The Crypto Key Stack plates are designed to be engraved—a process Crypto Key Stack claims will take around five minutes. Once engraved with a suitable tool such as a Dremel, the plates can be screwed together and stored in a safe place, and shouldn't need to be touched until the mnemonic seed is needed again. The engraving process is relatively simple, but we recommend practicing on a disposable metal surface first to get the hang of it.

According to Crypto Key Stack, the product has survived the likes of a butane torch, acid bath, and a 20-ton hydraulic press and remained legible, making it one of the most battle-tested metal wallets around. The Crypto Key Stack is available from the official store in a variety of bundles. The cheapest costs $44.99 and includes a single engraving plate, two blank cover plates, and a battery-powered engraver. The most popular setup—the Key Stack Stealth Explorer bundle—comes in at $69.99 for three engraving plates, two blank plates, and an engraver.

Our Verdict: 4/5

In terms of value for money, you can't go wrong with the Crypto Key Stack.

cryptokeystack.com

Cobo Tablet

The Cobo Tablet locks magnetically and can be rotated to reveal the BIP39 seed phrase (Image: Decrypt)

The Cobo Tablet is a sleek mnemonic storage device that can be used to keep 12, 18, and 24-word BIP39 recovery seeds safe from a variety of threats. Like many metal wallets, the Cobo Tablet is designed to store the first four characters of each BIP39 seed word.

Measuring a slimline 60 mm x 105 mm x 6.5 mm, the Cobo Tablet is one of the more aesthetically pleasing storage options available. It's constructed entirely out of 304-grade stainless steel, rated as fireproof up to 1455°C or 2651°F, resistant to most types of corrosion, and completely waterproof.

Unlike some of its rivals, the Cobo Tablet doesn't require any specialized tools to set up. Instead, owners simply need to press out the letters from the supplied metal sheet and insert them into the unit, after which they're secured in place with a screw-on cover. The Tablet can then be rotated shut to keep its contents hidden from view. The package also includes tamper-proof stickers, which can be used to reveal if the Cobo Tablet has been opened after sealing. The latest version also includes a padlock hole, which can be used to further secure the wallet.

At $39, the Cobo Tablet is by far the cheapest option on this list, making it suitable for those on a budget. However, for those looking to splurge, the Cobo Tablet can also be purchased in combination with the Cobo Vault hardware wallet—setting you back a rather more substantial $479.

Our Verdict: 3.5/5

The Cobo Tablet is an excellent budget option for those looking to securely store their Bitcoin recovery seed.

cobo.com

Blockplate

The Blockplate is an extremely robust metal wallet and is one of the simplest to use. (Image: Decrypt)

Many metal wallets require an intricate, fiddly setup process. Not so the Blockplate, which is just about as simple as they come.

It takes the form of a square, metal slab with the numbers 1 to 12 engraved on one axis, and A to Z engraved on the other to form a grid. Each unit is constructed out of thick 12-gauge 304-grade stainless steel and can store a total of 12 recovery words. Two plates can store an entire 24-word BIP39 recovery phrase, whereas a single plate is sufficient for a 12-word BIP39 seed.

Unlike some other metal wallets, the Blockplate is only designed to secure recovery words; it's not suitable for storing other kinds of confidential information such as private keys, passwords, or encryption keys since it cannot record symbols, numbers or different letter cases.

The Blockplate works by storing the first four letters of each recovery word—all that's actually required to successfully recover a wallet, since no two BIP39 words share the same first four letters. These letters are first marked on the Blockplate with a marker and can then be stamped permanently using an automatic center punch, which will leave a permanent dent in each box. The Blockplate doesn't come with an automatic center punch, but these can be purchased for an additional $10 on the Blockplate store—or for a few bucks at your local hardware store.

Each plate measures in at 84 mm x 78 mm x 2.8 mm and is heat resistant up to 2100°F, as well as being both water and corrosion-resistant. However, the Blockplate is not tamper-resistant like some other metal wallets, and does not come with a cover or case used to obscure the inscribed information. At $69 for a double pack, the Blockplate is one of the cheaper metal wallet solutions on the market—but this does come at the cost of reduced versatility.

Our Verdict: 3.5/5

The Blockplate represents a solid low budget option, but is only suitable for those looking to store a BIP39 seed phrase and nothing else.

blockplate.com

Hodlinox

The Hodlinox comes in single-plate (left) and double-plate (right) variants (Image: Decrypt)

The Hodlinox is a simple metal storage plate that is used to store Bitcoin (BTC) and other 12 to 24-word recovery phrases securely. It's available in a variety of designs, all of which are constructed out of thick, stainless steel and engraved with easy to read guidelines for seed words.

Unlike some other recovery phrase storage devices, the Hodlinox requires owners to manually engrave or stamp their seed phrase onto their plate, physically marking it onto the metal. 'Martin', the founder of the project, believes that this solution is more secure than assembling letters into a series, since there's no chance of the letters falling out of the storage medium.

Depending on your needs, the Hodlinox is available in a range of formats, ranging from the cheapest option, a single plate without a case at €29, to a double plate at €49, to the most expensive option—a pack of 10 double plates for €395. The website only accepts payment in Bitcoin.

The single plate option is double-sided with recovery words 1-12 written on one side, and 13-24 on the other side. The double plate option instead comes with two single-sided plates that are attached together with a screw, which would need to be unscrewed to view the recovery phrase. The Hodlinox also ships with a tamper-proof seal which will be damaged if the Hodlinox is forced open—either metal or plastic, depending on whether you're using a single or double Hodlinox setup.

Since the Hodlinox is constructed out of stainless steel, it's inherently water and fire-resistant.

Rating: 4/5

Costing just €29 for the single plate model, the Hodlinox represents great value for money. However, it is more secure when you use an engraver rather than a marker pen, so consider factoring that in as a cost.

hodlinox.com

CypherWheel

The CypherWheel uses a rotating disc to reveal each word of a 24-word seed phrase. (Image: Decrypt)

The CypherWheel is a robust metal wallet machined out of 5/16" thick stainless steel. Coming in at 191mm x 11.4mm x 7.6mm and weighing around 300 grams, the CypherWheel certainly looks and feels like a heavy-duty piece of equipment.

Although many seed storage tools are designed to feature as few moving parts as possible, the CypherWheel is different from most. Users of the CypherWheel need to slide the individual tiles for each letter of their private information into the wheel through individual ramps machined into its body. This is a rather fiddly process, but the CypherWheel is supplied with a pair of tweezers to make things easier.

There are 24 different segments in total, and the CypherWheel is compatible with both BIP39 and SLIP39 seed phrases, and can store up to 96 characters of confidential information. Once the tiles have been inserted, a supplied punch tool is used to lock the letters into place, preventing them from accidentally falling out.

Unlike most other metal wallets, the Cypherwheel can be used to store just about any sensitive information, which can include Bitcoin private keys, seed phrases, passwords, or anything else that can be formed from the letters A to Z. However, it is primarily designed for seed phrases, since each segment of the wheel is numbered from 1 to 24, just like a BIP39 recovery mnemonic.

Each word of the seed can be revealed by rotating an internal disc, and the entire unit can be locked using either the supplied security seal—which will break if the device is unlocked—or a standard padlock through the hole in the unit.

The CypherWheel is extremely solid, and waterproof, dustproof, and fireproof up to 2,000 degrees. However, all this security comes at a steep cost—200 on the official CypherSafe web shop. Nonetheless, if security is your top priority, then you will struggle to find a more versatile and robust metal seed storage solution.

Rating: 3.5/5

The CypherWheel is by far the most robust and most expensive option on this list. But if cost is no object, this is the one we'd pick.

cyphersafe.io

Ellipal Mnemonic Metal

The Ellipal Mnemonic Metal comes in a sleek flip-top format (Image: Decrypt)

As its name suggests, the Ellipal Mnemonic Metal is a metal cryptocurrency backup solution that allows owners to safely store their 12 or 24-word recovery phrase. It comes in an 86mm x 60mm x 8mm clam-shell form factor and is constructed primarily from aluminum.

According to its product description, the Ellipal Mnemonic Metal is designed to be fireproof, waterproof, and insect-proof, helping to keep the recovery phrase protected against most potential physical threats. However, although the Ellipal Mnemonic Metal has a durable build, it's not listed as crush-proof—though we were unable to manually bend the item while reviewing it.

The Ellipal Mnemonic Metal is designed to store the first four letters of up to a 24-word BIP39 recovery phrase. Since the first four letters are unique to each word in the BIP39 word list, it is not necessary to store the complete word to safely back up your mnemonic phrase. Many wallets will actually fill in the rest of the word automatically after typing in the first four letters during the wallet recovery process.

It comes supplied with a variety of letter stamps in addition to a screwdriver. Each letter is popped from its sheet and can be inserted into the case after unscrewing a numbered front-panel with the included screwdriver. Once all the letters are in place, the front panel can be screwed back on, and the entire wallet can be locked shut with a padlock (not included).

The Ellipal Mnemonic Metal currently retails for $49, but can be had for just $29 when purchased alongside the Ellipal Titan hardware wallet. As such, it's one of the cheapest metal wallet solutions on the market currently.

Rating: 3/5 

The Ellipal Mnemonic Metal is a robust, relatively inexpensive solution for storing 12-24 word seed phrases.

ellipal.com

D’CENT Card Wallet

The D'CENT Card Wallet can be used to store ether offline (Image: Decrypt)

Unlike the other options on this list, the D'CENT Card Wallet is designed specifically for Ethereum (ETH) and differs in the way that it keeps your funds safe. The Card Wallet comes in a credit card-like form factor with an Ethereum address and its associated QR code printed on the front, in addition to a PIN hidden beneath a scratch off panel.

Rather than requiring you to set up a hardware wallet or back up a recovery phrase using a metal storage solution, the D’CENT Card Wallet instead acts as a private key storage and authorization card. The device ships with a single Ethereum address and the private key associated with it, which can be used to store Ethereum offline. This private key is protected by an EAL5+ certified secure chip, which is able to communicate with a mobile device via a built-in RF antenna.

The D'CENT Card Wallet represents an interesting compromise between security and functionality. Alone, the card simply stores Ethereum securely offline, but can be combined with a dedicated mobile application used for managing payments. As such, the D'CENT Card Wallet makes it possible to store Ethereum offline, while also providing an easy access route to funds.

However, this does come with a significant compromise—D'CENT generates both the address and the private key of each D'CENT Card Wallet sold, and information on how it keeps this information secure is scanty. Nonetheless, at just $12.99 from the official D'CENT store for $12.99, the D'CENT Card Wallet could be a convenient option for storing and using small amounts of ETH.

Rating: 2/5 

At just $12.99 the D'CENT Card Wallet is extremely cheap, but the pre-generated private key is a no-go for us.

decentwallet.com