One string of characters separates a cryptocurrency holder from losing all his or her capital, and losing it permanently. That string is the private key, and more frequently these days, folks see it not as a random collection of letters and numbers, but as a little black-and-white square: a QR code. Whether or not you knew what you were doing, you’ve interacted with a blockchain private key QR code already if you’ve set up a hardware wallet, printed a paper wallet, or seen a cold-storage device flash a pattern at a camera.
In this guide, we take a deep dive into what these QR codes are, how they are created, how they are different from the QR code you can safely share in your receiving tab and above all, how to deal with one without becoming the next cautionary tale in a crypto security forum. From first time hardware wallet setups to cold storage considerations for a large holding and everything in between, there’s technically accompanied detail and practicality here, instead of recycled information. Let’s first begin with the basics.
What is a Blockchain Private Key?
A blockchain private key is a large random number that is used to demonstrate that a certain address on a blockchain has money belonging to it. The number is 256 bits long, which is too big to try out every one of them even with all the computing power today working together, and that’s for Bitcoin, Ethereum, and most other chains based on elliptic curve cryptography. There isn’t any rough guess, it’s just the mathematics of the keyspace, and that’s why it is believed to be computationally infeasible to brute force any private key with any existing technology.
The private key is not selected, it is generated, and preferably generated with a cryptographically secure random number generator. Once it exists, mathematics does the rest. Knowing the private key, a public key can be obtained by running the private key through elliptic curve multiplication. The wallet address that you would share with someone to receive funds is created by hashing the public key one or more times using a hashing function. The operation is unidirectional and cannot be reversed: You can always get a public key and address from the private key, but you cannot go back from a public key or address to the private key that generated it. That is the whole concept of blockchain’s asymmetry and ownership.
It’s as simple as this: the private key is the control of the money. There’s no password reset, no forgot my key recovery form, no customer support line that can override the underlying math. This is why the popular saying is “not your keys, not your coins,” meaning that if you don’t have the private key to your funds, say, for example, if they are stored on an exchange, then you are not in control and don’t have cryptographic ownership of your funds.
This is also why a private key QR code is handled with extreme care, much like the pivot of any other well-known information that one may carry. It’s not some kind of password that can be reset if it gets hacked. A bank cannot freeze and reissue it if it is not a credit card number. It is the full and final permission to access all assets associated with that key, and anyone who gets the key has exactly the same permission to access your assets as you do without any notice, without any permission, and without any ability to revoke it.
Private Key vs. Public Key vs. Wallet Address: Why the Difference Matters
The different types of wallet QR codes a crypto app can create are one of the most common sources of confusion, and at the same time, the cause of some truly devastating mistakes. There are three totally different things that are combined together and casually referred to as my wallet QR code, and they have totally different levels of risk.
The wallet address (receiving address) is the one that you share to receive funds. It comes from your public key and is meant to be put everywhere: on an invoice, publicly for a donation, or in a text message to your friend, it poses no danger to your holdings. Scanning another user’s address QR code and sending funds to them is the way cryptocurrency is supposed to be used, and by far the most popular QR code interaction in crypto.
The public key is one step up from that in that derivation chain. It is not usually included in a QR code in consumer wallets but can be found in more advanced setups, as it is used to generate addresses or to verify signatures without ever seeing the private key, such as multisignature and watch-only wallets. As with the address, giving out a public key does not give anyone the ability to access your money, but it does make it easier for an external observer to connect your transactions.
Here, the private key is the important one, and in modern HD wallets, the recovery seed phrase is used to generate the private key. This is the value that authorizes spending. It is never to be shared with anyone, anywhere, for any reason, including from a person claiming to be a support agent, a wallet recovery service, or a website that asks you to scan or enter a private key or recovery phrase to verify your wallet.
The real risk is that all three can appear to someone who doesn’t know the interface as a little black and white square on a screen. If a new user is asked to scan the wallet QR code during setup, they might not understand that this is a signing QR code from a cold wallet, and that the QR code they have scanned with friends a dozen times is a receive QR code. All good wallet interfaces describe them differently for this very reason, and this is the simplest thing one can do to avoid making terrible errors that can never be fixed.
Why QR Codes Became the Standard Way to Represent Crypto Keys
Prior to the popularization of QR codes in wallets, private keys and addresses were generally stored as text, as long strings of numbers and letters that were copied, mailed or even worse, typed by hand. Well over 30 characters can constitute a Bitcoin address, a private key in Wallet Import Format (WIF) is around 51-52 characters, while a raw hexadecimal private key is exactly 64 characters. When a single character is mistyped or miscopied, the address is invalid, and the transaction fails, or, in the very rare and extremely bad cases, funds are sent to an address no one can control or recover.
QR codes make this a simple solution. QR codes are two dimensional barcodes that were first developed in the 1990s for automotive part tracking, and can hold several thousand characters of data and are importantly designed with error correction built in. QR code has four levels of error correction, from about 7% error correction to as high as 30% redundancy, which means it can still be scanned even if it is partially smudged, creased or partially covered. This is important since a printed or engraved copy could be stored in a safe or drawer for years.
There’s no human element involved in scanning either. Since the exact bytes are encoded in the pattern and read by the camera, there is no need for keystrokes, autocorrect, line breaks from a text editor, or the potential for a character being misread, and the bytes are directly passed to the wallet software. The ‘l’ and the ‘1’ are almost indistinguishable in many fonts, and cryptographic strings don’t allow for such substitutions, unlike regular text.
Especially for crypto, this compactness, damage-resistance, and typo-removal made QR codes the obvious choice not only for data that users use freely, such as addresses, but also for data that demands extreme care, such as private keys and seed phrases. Both are based on the same technology, but the content and the way it is handled should be different.
How can a private key actually be converted to a QR Code?
The creation of a private key QR code is primarily an encoding process rather than a cryptographic process. The QR code is just a container for the result, the hard cryptographic work to generate the random key itself takes place first. However, the format in which the one that is encoded depends on what is being displayed, and that is why it is important to learn the differences.
The most literal is a raw hex private key, which is 64 hex characters (0-9 & a-f) that represent the underlying 256-bit number directly. It’s precise but unforgiving. No inbuilt checksum: if someone attempted to type it (as opposed to scanning it), a single transcription error would go totally undetected until the money was gone.
The WIF (wallet import format) is a Bitcoin-specific encoding, which wraps the raw key with a version byte and a checksum, then encodes in Base58, a character set that excludes visually similar characters, such as O and 0, I and l. WIF is a shorter key format to use and the keys are also protected against errors, reason why many legacy wallet exports and paper wallets use the WIF format.
A BIP39 mnemonic phrase is yet another thing, and that is what most modern wallets produce and QR code nowadays. Instead of a private key, a seed phrase is a string of 12 or 24 words from a list of 2,048 common words that represents the master seed in a Hierarchical Deterministic (HD) wallet as specified in BIP32 and BIP44. The wallet can generate a seemingly endless series of private keys and addresses from that one seed – all recoverable from the 12 to 24 words. This is why modern wallets refer to backing up your recovery phrase instead of backing up your private key, because the recovery phrase serves as the master key for each key the wallet will create.
The encoding itself is straightforward in either of the formats. The characters (hex or WIF or space-separated mnemonic words) are passed to a QR code generation library, which maps characters to the matrix pattern as per the QR standard, adds error correction and positioning markers and outputs an image. This process does not provide any kind of security. A QR code is as safe or vulnerable as the text that it contains. The QR code itself doesn’t encrypt or protect the key, it simply makes the same sensitive data easier to transport between an offline generation environment and what is physically stored, without ever having to type a key.
The various types of private key QR codes you will encounter
Not all private key QR codes are alike, and knowing the kind you’re using dictates its use.
The original consumer-facing use case was a paper wallet QR code. The key pair is generated by a generator, hopefully offline and the address and the private key are printed on a sheet of paper as a QR code, along with the human-readable strings. They were a popular choice for long-term cold storage in the early to mid 2010s. They’ve gone out of style with security-minded users for a very simple reason: paper is flaky, a single sheet is a single failure point and it’s very difficult to create paper securely, even if using a machine offline, with trusted software and then securely destroying the digital record.
These are now known as seed phrase QR backups. Some hardware wallets and third-party backup tools can QR-code the 12- or 24-word recovery phrase for quick reentry on a new device instead of having to type each one into the device. Some metal backup products allow you to print the QR pattern directly, as well as print the word-by-word text.
Air-gapped signing QR codes are the most prevalent experience of anyone using a modern hardware wallet for cold storage, and they need special attention as they are often misunderstood. In this workflow, the unsigned transaction is QR-encoded using an online “watch-only” companion application, scanned by the offline signing device, signed on board using the private key, which never leaves the device, and the result is then displayed as a QR code and scanned back by the online application. This process doesn’t actually involve the private key being directly encoded as a scannable QR code instead, the QR codes convey transactional information only, which is what makes this design secure to begin with.
Caution is required when using exchange or custodial export QR codes. Some centralized platforms allow users to export a private key, for a custodial or self-custody wallet feature built into their app, as a QR code for backup purposes. This is because it is an operation performed within an internet-connected app on an internet-connected phone and it’s important to treat any export from this platform as an offline hardware wallet export, even if it is not called for by the platform’s UI. Doing so will give it the protection it needs.
Why Private Key QR Codes are so handy, and so risky
Let’s take a moment to understand why this particular format is both beloved and the root of some of the biggest losses in cryptocurrencies. The convenience is true: a QR code can be scanned in less than one second, transcription errors are avoided, and two devices can share complex cryptographic information without ever connecting to each other or the Internet. The last is the whole point of having air-gapped hardware wallets: QR codes (and microSD cards on some wallets) are the way an entirely offline device can be involved in an online transaction.
The risk is related to the same properties. A QR code can be read by any camera in an instant and without needing any software. No, not part of it, they just saw a little of it. A single shot from a camera, whether of a phone or a high-resolution security camera or a video recording at a glance using the code in the background or simply a screenshot taken by malware, is all that’s needed to get the entire key in one shot. This means that there is no second factor to prevent the key from being exposed due to the loss of the money, other than some form of “extra security” such as a passphrase or a multisignature wallet.
Compare that with a bank account or a bank vault, where it is generally understood that if they are hacked, you can detect the hack and reverse it. A bank may determine suspicious activity, freeze an account, or provide a new card. By design, however, a blockchain lacks all of these safety nets, and that’s what makes it permissionless: the need for such a trusted intermediary is the whole point. The downside of cutting out the middlemen is that the individual key holder takes on all the responsibility that was previously held by a bank’s fraud department. A private key QR code is at least for a brief moment physically visible, and that’s why it’s worth being extra careful with, even though it’s super convenient.
How Air-Gapped Cold Wallets Sign Transactions Offline with QR Code
It is this where QR codes do some of their most advanced work in the cryptocurrency world, and understanding how they work is important, even if you aren’t going to use one to build your own fully air-gapped system.
It’s an air-gapped wallet, which means it has no USB data transfer, no Bluetooth, and no WiFi. The devices based on this principle generate and store the private key on hardware that is not, and never has been, networked in any way. Data can only be transferred in and out visually by the device’s camera and screen or physically by an microSD card. For instance, Keystone’s hardware wallets are purpose-built around QR code communication, in addition to supporting multisig via PSBT, and are an official partner of MetaMask as a hardware wallet for Ethereum and other EVM-based signing. SeedSigner goes a different, completely open-source, DIY route: It’s based on a special, minimalist Raspberry Pi Zero board with no WiFi or Bluetooth hardware, only a basic camera that is used to exchange a QR code with another SeedSigner. Foundation’s Passport devices take it one step further: they are completely open source, and have no USB, no Bluetooth or NFC, and no wireless radio whatsoever all transactions are done using a QR code or a microSD card.
In the signing flow, typically, a companion app or a desktop wallet that is kept online at all times but does not hold the private key generates an unsigned transaction and shows it as a QR code. The QR code is scanned by its air-gapped camera and the transaction information is displayed on the screen for the user to approve: destination address, amount, network fees, and, after the user approves physically on the device, the private key is used internally to sign the transaction. The transaction is signed and then presented as another QR code to be scanned by the online companion app and broadcast to the network.
The private key never leaves the offline device and the offline device never touches the Internet. The attacker can observe the transaction that is being requested, but can’t create a valid signature without having the hardware device, and on most implementations, a PIN as well, because the hardware device and the computer it runs on could be totally infected with malware.
Some transactions, such as multisig transactions or other transactions with extra data, do not easily fit into the practical space of a single QR code, so several devices have an animated or sequential QR format. The most popular of these is the Uniform Resources (UR) standard devised by Blockchain Commons, which separates data into a series of QR frames that are presented one after another. The receiving camera can reconstruct them in a fountain code style, which means that they can even be received somewhat out of order. If you’ve seen a hardware wallet scrolling with a bunch of QR codes while setting up or signing, this is what’s happening under the hood. Not all air-gapped devices are based on QR at all: Coldcard, for example, is designed around microSD-card-based data transfers, which serve the same purpose as QR codes but use a different physical medium.
The Safe Way of Creating a Private Key QR Code
The generation environment is equally important as the wallet software when it comes to setting up a new hardware wallet, or to create a cold storage backup, or migrating between wallet formats.
If possible, use a dedicated, offline device. Ideally, this will be a screen on the hardware wallet and a generator that is intended for this purpose and that does not show the key on an arbitrary computer at any time. If software-based generation is used, it should be run on a machine that is not connected to WiFi or Ethernet and preferably one that has not been used for any other purpose or has been freshly wiped.
Verify the tool before you trust it. If possible, open-source generators allow you or a security researcher to look at the source code, while downloaded versions can be compared to published checksums, if available, and web-based generators should be avoided. One of the more insidious methods employed is a compromised or intentionally malicious generator that creates a seemingly random key, but in fact, it is.
Do not create a private key on a site that you visit every time, including a good one, without being able to save it locally and run it offline afterwards. While browser-based generators are useful, any browser add-on, malicious ad script, or infected page could, in theory, see the random value as it is being generated.
Don’t leave behind a digital footprint. If a key is there, do not save it as a file, screenshot or photo, even for a short time, to print the key out on any internet-connected device. If you have to print directly from the offline generator to a printer that doesn’t have WiFi or internal memory to store print jobs, then you have undone a lot of the reason for generating the key offline in the first place.
Create multiple QR code physical copies, multiple print / engraved copies, rather than relying on one print / engraved QR code, as discussed more in detail below. Afterwards, make sure to wipe any temporary files, clear the history of the clipboard and, if a live-boot offline operating system was used for the process, avoid saving any session data at all.
Importing vs. Sweeping: What to Do With a Private Key QR Code You’ve Scanned
Most wallets have two slightly different options when you scan a private key into a wallet app using a QR code, and this makes a difference that most users don’t understand.
Importing a private key is putting that private key into your wallet software to use, thus, the same key is used in the future any future transactions will still use the same key. While quick and easy, if the key ever gets into the wrong hands at any point along the way, a shared photo, being exposed on a screen, a synced generation environment, or a compromised generation environment, the imported wallet is too. It does not remove the risk as you’ve now begun to actively use a key that may be compromised.
Sweeping a private key does something different. This wallet decodes the old key, checks the balance and spontaneously creates a new transaction, all the funds to a completely new address that is generated by a new key, which has never been published anywhere. The old key is thus effectively retired. The recommended way to do it is any time there’s a reasonable chance a key has been in a position of potential exposure, which is nearly every paper wallet or manually-generated key that’s been stored anywhere for any length of time and/or passed through more than one hand.
The general rule that most of the wallet guides with a security-focused mindset agree on is the following: If you’ve ever printed, photographed, typed, or displayed a private key outside of the internal signing process of a purpose-built hardware wallet, it is considered seen, and you should sweep, rather than import, if you’re consolidating and/or reactivating funds from it. It comes with a small transaction fee and a few seconds is nothing compared to giving up relying on something whose history of use you can’t fully know with a key.
The Most Common Ways People Lose Funds Through Private Key QR Codes
Most QROPP losses are not the result of cryptographic attacks from outside the ordinary. They are based on a few common human errors.
One of the most common causes of panic and sometimes actual loss, especially among new users who are configuring their first wallet, is to mistake a private key QR code for an address QR code. It only takes a few seconds to read the label on the screen before scanning or sharing the key, if it’s Receive or Address, private key, recovery phrase or backup, and it will save an entire class of mistakes.
Along with the rise of QR code usage and the expansion of QR-code-based phishing, or quishing, crypto users are a favorite target. The trick is to replace a legitimate QR code with a malicious one: a sticker over a code at a crypto ATM or kiosk, a mock code in a phishing e-mail disguised as a wallet security alert, or a fake code in a scam social media post as a purported wallet verification code. In particular, the U.S. federal government has issued a warning regarding the use of QR codes at physical sites, such as cryptocurrency ATMs, that are modified to divert users to attacker-controlled locations. In the case of a cryptocurrency QR code, scanning the QR code does not automatically install anything and instead presents the victim with a fake wallet asking them to “reconnect” or “re-verify”, after which the victim enters their seed phrase, which is then captured by the attacker, or the QR code itself is simply swapped out with the attacker’s own receiving address, which the victim will pay into without realizing it.
A related but different threat is fake wallet and paper wallet generator sites. Some bad sites and sometimes bad mobile apps create a new, random key and QR code, but in reality, the “random” key was actually prearranged and the attacker is waiting for the money to come into his account. The interface is exactly like a real generator, so the only way to stay safe is to get the tools from verified, reputable, preferably open-source generators and not the first one you find online. Before funding whatever address a generator produces, it’s worth running it through a dedicated checker such as Crypstudio’s wallet address scanner a quick scam-database lookup catches a compromised or already-flagged address that a slick, legitimate-looking interface alone won’t reveal.
Even a lot of otherwise careful setups are undermined by the cloud photo backup. People tend to forget that most phones automatically upload photos to a cloud service when they take them for a QR code, just as a backup, just for a moment. That picture and the key or seed phrase contained within are now stored on a server over which they have no control, and bound by the strength of the password, two factor authentication setup, and the cloud provider’s security practices that were not part of the original threat model when the wallet was set up.
The more serious threat is malware that has access to a camera, screen capture or the clipboard, especially for those who have a lot. Monitoring the contents of the clipboard to replace the wallet address with an attacker’s when a user pastes a wallet address into it is well-known and documented, and camera-based key theft is not theoretical, though it is less common, especially in compromised or jailbroken devices.
Lastly, when printing at a common or commercial printer, a hotel business center, an office shared with colleagues, or a copy shop, the private key is sent via a device, and often a network, which the key holder does not control, and which may store print job information. A handy shortcut to undo most of the good work done in generating the key offline.
How to store a Private Key QR Code long-term: Best Practices
Creating a key securely is just one half of the equation. Security of the physical or print copy is what really keeps it safe for months and years.
Look for metal rather than paper for anything that is long-term. Paper deteriorates due to fire, moisture, fading and ripping. In the real world, paper wallets have failed numerous times, so many wallet manufacturers that are used to security would prefer to spend more for stainless steel backup plates that will withstand house fires, flooding, and years of storage. In addition to, or in place of, word-by-word text, products such as Billfodl and others with metal backing plates can be stamped and/or engraved with a QR pattern, which provides the same scan-to-import convenience with added physical durability.
Think of distributing the key material, don’t keep an entire copy of it in one location, and know that there are actually two different tools for this, not one. Shamir’s Secret Sharing, which is also supported by Trezor’s parent company and included in several other hardware wallets, mathematically distributes a single seed across multiple recovery shares, where a certain number of them (let’s take 3 out of 5 as an example) can be used to generate a single seed. A single share isn’t enough, nor is a single stolen or lost location. To be precise here, SLIP39 is a backup-splitting technique that can be recovered with a single device once the necessary shares are collected, and it’s not the same as multisig, which is described below.
Store in tamper-evident containers any items that are not under your full supervision, like a safe deposit box. Tamper-evident bags and seals will reveal if a backup has been accessed even if there is no apparent evidence of tampering.
Create geographic redundancy to withstand a disaster in one location, such as a fire, flood, theft, or natural disaster, that renders the single location where a backup was stored unusable. If the copies or Shamir shares are held in two or more secure storage facilities, whether a safe in a home or a bank deposit box, or two trusted family members’ secure storage, that single point of failure is eliminated, but the number of places that a complete usable key exists is not meaningfully increased.
Don’t name a backup what it is! A metal plate or envelope labeled Bitcoin private key or crypto seed phrase is clearly a target for anyone with physical access, including a contractor, burglar, or inquisitive grandparent. A simple step that can meaningfully decrease risk is to store under neutral or no label.
Do not digitally copy, just in case. When it comes to photos, a password manager entry, or a cloud note, it’s easy to simply keep it as a convenient backup of a backup. Each of these reintroduces the very same thing the internet-connected generation and physical storage were meant to take out in the first place.
Multisignature Wallets: Spreading QR-Based Key Risk Across Multiple Devices
As the problem of a single point of failure is one that affects all wallets, regardless of the storage method used for a single key, multisignature wallets handle it in a different way. A multisig wallet will have a group of truly independent keys, e.g. 2-of-3 or 3-of-5, that must sign a transaction in order for the wallet to recognize it.
In practice, this translates to three distinct hardware devices, each containing its own private key that is used to generate a specific public key, and each interacting with the signing coordinating wallet software through a QR code exchange, as outlined above in the air-gapped signing. Funds can’t be moved by a single device, a single QR code or a single physical location. As long as one of the devices is lost or its key is completely compromised, and the other keys of the system are not obtained by the attacker, then there will be no risk to the funds.
The difference between this and Shamir’s Secret Sharing (above) is that SLIP39 allows for one key to be split into multiple pieces, which are recoverable and put together by a single device for backup purposes, while multisig uses multiple complete and independent keys that sign separately without any reassembly step at all. They solve different problems that are related, and some reasonable setups use both, for example, a setup consisting of a 2-of-3 multisig with one of those three keys being protected by a Shamir backup.
This is also a structure that alters the math of QR code exposure in particular. Even if a person’s partial signature is exposed in a 2-of-3 scheme via a phishing attack or capturing the QR code with a camera, they cannot spend funds on their own since they only ever have access to their own QR code of the three. A second independent device and its security practices would have to be compromised as well.
The tradeoff is complexity. To properly set up and recover a multisig wallet, it is more important to document which is which device, how it’s configured, what coordinating software is used, etc., than it is for a single-key wallet, and losing documentation of that setup can be as destructive as losing a single-key backup. Multi-sig is widely considered to be the more robust architecture and is considered by security-minded crypto users as such, especially for holdings large enough to warrant the added operational overhead: because it changes “one QR code, one point of failure” into a threshold problem which a potential attacker must solve several times over.
QR Codes vs. NFC vs. Manual Entry for Managing Crypto Keys
QR codes are not the only means of transferring key-related data between devices and it is useful to know how the key alternatives line up.
The slowest and most prone to error is by manual entry, typing in a private key, WIF string, or seed phrase, which doesn’t require a camera, wireless radio or any hardware capabilities at all. The primary benefit of it is that it could be used on virtually any device that has a keyboard. The primary threat, aside from typos, is that typing such a string on a system that is connected to the Internet puts it at risk from keyloggers, clipboard monitors, and on-screen keyboard prediction or logging functions that are absent from offline camera scans.
A smaller number of hardware wallets use a technology called NFC (Near Field Communication), which allows signed transaction data to be transferred by tapping the device against a phone, instead of scanning a QR code. While this is quick and doesn’t involve setting up a camera, this system involves a short-range wireless radio transmission, and there are users who are security-aware who would prefer not to be doing anything wireless at all, opting instead for QR’s purely visual and one-way data transmission. Different implementations give different amounts of information and how long the radio stays ‘on’ will vary, and may be more significant for threat models where the radio needs to be very near the body rather than for typical applications.
QR codes are a middle ground and, as such, have become the dominant standard for air-gapped signing, particularly. There is no wireless radio at all, it is purely visual/optical exchange. They’re fast enough to be used in practice, they are robust against partial damage with built-in error correction, and they are simple enough to be implemented at even a low cost open source hardware wallet without any radio hardware. QR codes also have a very real smaller attack surface than USB, NFC or Bluetooth: There is no data protocol that can be exploited, a camera either reads a valid pattern or it does not. The primary constraint is the ability to carry very large data payloads, which is achieved using the animated multi-frame QR technique discussed above and not because of any inherent limitation of the QR for typical single-key or single-transaction applications.
The reality is that for most cold-storage solutions, the decision is which hardware wallet you want to use, and not an actual security compromise. It is clear that QR-based signing and well-designed NFC-based signing are vastly more secure than any signing process using typing of a private key on a connected device.
Planning for the Unexpected: Inheritance and Backup Redundancy
There is another type of risk with a private key QR code: what happens if its owner suddenly becomes unavailable, whether by illness, accident, or death, and no one else knows that the funds even exist or how to access them? A blockchain wallet isn’t like a bank account, so there is no inherent estate procedure that will bring a wallet to light. If the key material were lost, along with the owner, then the money is gone forever.
It’s a real design challenge to solve this without compromising day-to-day security, and there are a few solutions available. Sealed instructions, held with an estate attorney or even at a place recognized by a designated executor but maybe not offered to the executor daily, allow money to be recovered after a specific triggering event such as death or incapacitation without revealing a key whilst the owner remains alive and capable of acting directly.
Multisig arrangements can include an inheritance-specific key: For instance, a 2-of-3 scheme where the third key is kept by an attorney or a trusted family member or by a specialized inheritance service that would only be used if the first person is no longer able to access it, and the second agrees to reconstruct access. This prevents giving any one party full access to the other, but does retain a documented recovery path. In the same way, the various shares distributed to different trusted parties work, a certain number of them have to combine to reconstruct the seed, if necessary.
In either case, the directions (how-to) on how to actually get access to the key material should be carefully retained. If your loved one has a secure metal backup or a set of Shamir shares, but doesn’t know about it, or doesn’t know what wallet software or derivation path to use, or doesn’t know that a 20 or 24-word list in a safe deposit box is worth much more than all the other contents of the box, a perfectly secured metal backup is useless.
Evolution of Private Key QR codes: Standards, Animated QR and Quantum Concerns
The manner in which private keys are encoded and transported through a QR code is still continuously changing, with a lot of effort going into the multisig and hardware wallet landscape towards becoming more interoperable. Output descriptors are now often QR encoded often in the animated UR format, which allows for different brands of wallet software and hardware to interoperate within the same multisig configuration, without vendor lock-in. This is the part that is relevant to the QR code conversation, as it is introducing the ability to encode more than just a key or transaction in the QR code but also full wallet configurations that can be easily carried.
Standardisation initiatives for these formats, in large part spearheaded by actors like Blockchain Commons, will make sure that a particular hardware device, coordinating wallet and backup format are compatible with each other even as individual products evolve and become discontinued, which has been a theme throughout this guide.
But post-quantum cryptography is a more speculative issue that arises in longer-term conversations. Although currently the elliptic curve cryptography used by Bitcoin, Ethereum and any current blockchains is not thought to be vulnerable to any classical computers, if a sufficiently powerful quantum computer were available to run the appropriate quantum algorithm, it could, in theory, calculate a private key from the associated public key, which would effectively reverse the one-way property that has underpinned this entire guide. As of yet, there are no quantum computers that can do that, with estimates of when or even if they will be available ranging widely throughout the research community. Nevertheless, the prospect has already spurred some initial efforts to create quantum-resistant signature schemes and migration plans in various blockchain ecosystems. None of this alters the private key QR code guideline of today in any way, but it’s a sensible component of the big picture of honesty, longer range, for anyone doing multi-decade cold storage.
Private Key QR Codes: A Practical Security Checklist
Each rule in this guide is summarised in a short set of easy-to-say habits, and only marginally more difficult to follow consistently.
Use trusted and, wherever possible, open-source tools to generate private keys and seed phrases offline, and never on a device that is connected to WiFi, Bluetooth or cellular data during the process. If you’re scanning or inputting a QR code into a crypto wallet, read the on-screen label: Receive or Address is usually safe to share, but Private Key, Backup, or Recovery Phrase is never safe. Do not take a photo, screenshot, email, message or cloud store a private key or seed phrase QR code for any period of time. Use physical backup media (metal, not paper) and use multiple backup media in multiple secure, geographically different locations, not one. Sweep, don’t import, from a key that has been printed, displayed or handled outside the signing process of a hardware wallet as a potentially exposed key. For larger holdings where multiple QR codes or locations would not be a total point of failure, look into multisig, Shamir’s Secret Sharing, or even both. Write a recovery plan for those who would need it in your absence, but don’t allow day-to-day access for anyone while you are present.
All of this is non-technical and none of this has any real impact on the day-to-day use of a good hardware wallet. What it needs is to be used as a private key QR code deserves to be used: not as a convenient screen to be scanned and go, but as the most significant data in the entire transaction. We’ve now followed the path of blockchain private key QR codes from generation to long-term storage. The concept behind it is quite straightforward, although the cryptography may not be: The format evolves, but the accountability of having a private key does not. As always with security or self-custody decisions for real money, it’s always best to confirm the wallet-specific instructions directly with the wallet manufacturer before taking action, as interfaces and recommended workflows change over time. And for the wider picture beyond QR codes specifically, our crypto wallet security guide walks through the rest of the self-custody stack, from choosing a wallet type to everyday account hygiene.
