How does your crypto land in the right wallet when you send it across the blockchain? That’s the magic of public keys, and the math behind asymmetric cryptography at work. It’s invisible, but it does all the heavy lifting with your funds—securing them, verifying transactions, and keeping out bad actors. You don’t need to be a coder to get it, but you do need to know how it works to stay in control.
What Is a Public Key in Crypto?
In crypto, a public key is a cryptographic code that acts like your crypto identity. It’s a long string of numbers and letters, and it’s one half of a key pair—the other half of which is your private key. Your public key is unique because it doesn’t unlock or control your funds. It’s designed specifically to be a shared key that you can give to others in the form of a wallet address, and its job is to link you to the blockchain while keeping your connection secure and safe.
The strength of the public key comes from the math behind it. It’s created directly from your own private key through a one-way function. But you can’t reverse the process. Cracking the private key from the public one is basically impossible—even if all the world’s computers work on it at once, it would take longer than the age of the universe.
What Is the Purpose of a Public Key?
The public key’s main purpose is to prove something is true, without giving anything away. This is the core of asymmetric encryption, and it’s what lets others send you crypto without asking you to make an account with a bunch of personal info.
A public key has two main functions:
- First, it’s used for verification. When you digitally sign a transaction with your private key, your public key steps in to confirm that it was really you to everyone else. The network checks the math. If it all adds up, the transaction goes through.
- Second, it’s a tool for encryption. If someone wants to send you a private message or encrypted data, they can use your public key to lock it. Only your private key can unlock and read it.
Your public key doesn’t control your crypto or move your funds like your private key. But it can tell the network, confidently, “this person’s legit.”
How Public and Private Keys Work Together
Public and private keys are always a team. They work together to keep your crypto secure and your transactions verifiable. One key talks to the world, while the other proves you’re the one in control of your money to others.
Here are their core functions:
- Your private key is what you use to actually sign and send transactions.
- Your corresponding public key is what people use to send you crypto or verify your digital signature.
This setup is called asymmetric key cryptography. You digitally sign with the private key, and others verify with the public key. That’s all there is to it.
Let’s say you send someone your Bitcoin. Your wallet signs the transaction with your private key. The network checks that signature against your public key. If it matches, it goes through. No need to log in, call support, or click “verify my identity.”
What you sign with a private key can’t be faked. What you don’t sign can’t be verified with your public key and spent. That’s the beauty of a key pair. You stay in control, and the math keeps everything airtight.
How a Public Key Is Created
A public key is born from a private key—which is itself a long, random string of letters and numbers. From there, your wallet runs it through a mathematical algorithm. Specifically, it uses elliptic curve multiplication on a curve called secp256k1. The result of that process is your public key. Clean, predictable, and mathematically tied to the private key—but impossible to reverse.
This is real cryptography, and the math behind it is no joke. For Bitcoin and Ethereum, the private key is a 256-bit number. That’s around 10⁷⁷ possible combinations—way too big to brute-force.
Once the public key is created, it’s either compressed or uncompressed, depending on the format. Ethereum uses uncompressed. Bitcoin usually compresses it to make things shorter and easier to handle.
The key point is, though, that your public key is always generated from your private key—never the other way around. That one-way function is what makes it safe. Even if someone has your public key, they can’t work backward to find your private one. It’s computationally infeasible.
Public Key or Wallet Address?
Public keys and wallet addresses get mixed up all the time. They’re related, but not the same thing.
Your public key is a long, raw cryptographic code. Your wallet address is a shorter, cleaner version derived from that key. Think of it like this: the public key is your full name, and the address is your initials. You don’t need to write out your full name every time to get paid, since the blockchain can automatically trace your address back to the real you—your public key.
In Bitcoin, your wallet address is made by hashing your public key twice—first with SHA-256, then with RIPEMD-160. After that, it’s encoded, and the final product looks something like this:
“1A1zP1dP5QGefi2DMDTfTL5SLFv7DidfLa”
Ethereum takes a different path. It uses Keccak-256 to hash your public key, then grabs the last 20 bytes. That becomes your public address. It usually starts with 0x, like this:
“0xde0B295689a9FD93d5F28D9Ec85E40f4cb697BZe”
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What Is a Public Key Used For in Cryptocurrency?
In crypto, your public key has two main uses: receiving funds and proving that a transaction is valid.
When someone sends you digital assets, they use your public address, which is generated from your public key. The blockchain records that transaction and locks the funds to that public address. You won’t need to approve anything manually—the protocol handles it automatically. Only the private key linked to that public key can unlock and move those funds.
Also, a public key is used to verify digital signatures. When you sign a transaction with your private key, your public key confirms that the signature came from you. The network runs the math, and if it checks out, the transaction goes through.
Some systems also use public keys to encrypt and decrypt messages. Only the corresponding private key can decrypt and read it. Whether it’s verifying ownership or encrypting messages, public keys support secure, independent control of your assets.
Examples of Public Key Uses
Public keys aren’t just cryptographic theory—they’re used constantly in real crypto transactions. Here are some common ways they show up on-chain to help you understand why they’re so crucial.
- Bitcoin Transactions.
Say you receive Bitcoin at a public address like this:
“1ATobtBrgHqpTPbhG8JFpKqeZH4PYNiytU”
That address is a hashed version of your public key. When you spend the funds, your wallet includes your public key and a digital signature. The network checks that the key matches the address and that the signature checks out. - Ethereum Signatures.
Ethereum does things a little differently. Your public key is used to create your address. When you send a transaction, the signature reveals the public key, and Ethereum verifies it against the sender’s public address. - Multisig & Watch-Only Wallets.
Multisig wallets require multiple public keys to approve a single transaction. A 2-of-3 setup needs any two keys to sign. You can also use an xpub to create receive-only wallets that monitor funds without spending access (per BIP32).
Is a Public Key Safe to Share?
Yes, your public key is completely safe to share. Public key cryptography is designed to be that way, in fact. Sharing it doesn’t expose your funds, your identity, or your private key. And in most crypto systems, public keys aren’t exchanged between users directly anyway. Transactions happen using addresses, not raw keys.
When you give someone your public address, you’re sharing a shortened, hashed version of your public key. But even if someone has your full public key, they can’t use it to move funds or create valid digital signatures. Only the corresponding private key can do that.
So you can go ahead and share your public address when someone wants to send you crypto. That’s exactly what it’s for.
Common Myths About Public Keys
There’s a lot of confusion around public keys—what they do, what they don’t, and how safe they are. Let’s clear up some common myths to help.
- “If someone has my public key, they can steal my crypto.”
Wrong. A public key can’t move funds. Only your private key can authorize a transaction. - “Your public key and wallet address are the same thing.”
That’s not quite right. Your wallet address is a hashed, shortened version linked to your public key. They’re connected, but not identical. - “It’s possible to figure out a private key from a public key.”
Not in the lifetime of this universe. The cryptography behind public and private keys makes them entirely infeasible to reverse-engineer. - “I need to back up my public key.”
You don’t. Your wallet can regenerate it from your private key or seed phrase.
Final Thoughts
Public keys do a lot behind the scenes. They let you receive crypto, help the network verify your transactions, and encrypt data—all without ever giving up control. That’s the beauty of public-key cryptography: one key talks, the other acts.
So yes, sharing your public key with others is what you need to do to receive crypto. Just remember: your private key is the one that locks the vault. Protect it, and you’re good.
FAQ
Can someone steal my crypto if they have my public key?
No, they can’t. Your public key can’t move funds—it just receives them and verifies signatures.
How do I find my public key in my crypto wallet?
Most wallets display it under account details or settings. Some display the public address instead, which is derived from the public key.
Why do I need both a public key and a private key?
The public key receives and verifies, while the private key proves ownership and signs transactions. They work as a pair.
What happens if I lose my public key?
Nothing critical. Your wallet can recreate it from your private key or seed phrase. But if you lose your private key, it’s game over. You won’t be able to recover your funds in any way.
Can public keys ever be hacked?
Not with today’s tech. Reversing a public key to find the private one is mathematically infeasible—it would take billions of years.
Disclaimer: Please note that the contents of this article are not financial or investing advice. The information provided in this article is the author’s opinion only and should not be considered as offering trading or investing recommendations. We do not make any warranties about the completeness, reliability and accuracy of this information. The cryptocurrency market suffers from high volatility and occasional arbitrary movements. Any investor, trader, or regular crypto users should research multiple viewpoints and be familiar with all local regulations before committing to an investment.
