A public key is a cryptographic identifier mathematically derived from a private key that can be freely shared and is used to generate wallet addresses and verify digital signatures. In cryptocurrency, your public key (or the address derived from it) is what others use to send you funds, while only the corresponding private key can authorize spending those funds.
How It Works
Public keys are produced through asymmetric cryptography — a system where two mathematically linked keys serve different roles:
- The private key is generated randomly (256-bit number).
- The public key is derived from the private key via elliptic curve point multiplication on the secp256k1 curve (used by both Bitcoin and Ethereum).
- The wallet address is derived from the public key through one or more hashing steps (SHA-256 + RIPEMD-160 for Bitcoin; Keccak-256 for Ethereum).
The critical property: the public key cannot be reverse-engineered to reveal the private key. This makes it safe to share publicly.
Address Derivation
| Blockchain | Hash Function | Address Format | Example Prefix |
|---|---|---|---|
| Bitcoin (P2PKH) | SHA-256 ? RIPEMD-160 | Base58Check | 1… |
| Bitcoin (P2SH) | SHA-256 ? RIPEMD-160 | Base58Check | 3… |
| Bitcoin (Bech32) | SHA-256 ? RIPEMD-160 | Bech32 | bc1… |
| Ethereum | Keccak-256 (last 20 bytes) | Hex | 0x… |
A wallet address is a shortened, encoded version of the public key — not the public key itself. This additional hashing provides an extra layer of security.
Sharing Safely
You can share your public key or wallet address freely. It is designed to be public. However:
- Never confuse your public key with your private key or seed phrase.
- Verify addresses character-by-character when receiving — clipboard malware can substitute addresses.
- Use QR codes to reduce transcription errors when sharing addresses in person.
History
- 1976 — Diffie-Hellman key exchange published, establishing the concept of public-key cryptography.
- 1977 — RSA algorithm created, becoming the first widely adopted public-key cryptosystem.
- 1985 — Elliptic curve cryptography (ECC) introduced independently by Neal Koblitz and Victor Miller, offering equivalent security with smaller key sizes.
- 2008 — Bitcoin whitepaper released by Satoshi Nakamoto, applying ECDSA on secp256k1 for transaction authentication.
- 2009 — First Bitcoin transaction — Satoshi sends 10 BTC to Hal Finney using public key addressing.
- 2012 — BIP-13 introduces P2SH addresses (prefix “3”), enabling multi-signature and script-based transactions.
- 2017 — SegWit activation introduces Bech32 addresses (prefix “bc1”) on Bitcoin, improving efficiency and error detection.
- 2021 — Taproot upgrade activates on Bitcoin, introducing Schnorr signatures that enhance privacy by making multi-sig outputs indistinguishable from single-sig.
Common Misconceptions
“A public key and a wallet address are the same thing.”
A wallet address is derived from the public key through hashing. They are related but not identical. The address is shorter and includes error-checking features.
“Sharing your public key is risky.”
Public keys are designed to be shared. They cannot reveal your private key. However, reusing addresses (which expose the public key after spending) can reduce privacy by linking transactions.
“Each wallet has only one public key.”
Modern HD wallets derived from a seed phrase generate a new key pair for every transaction, improving privacy by avoiding address reuse.
Criticisms
- Complexity for new users — the relationship between private key, public key, and address confuses newcomers and leads to errors.
- Address format proliferation — Bitcoin alone has multiple address formats (Legacy, SegWit, Taproot), creating compatibility friction.
- Quantum computing threat — public keys exposed on-chain could theoretically be vulnerable to future quantum attacks using Shor’s algorithm, though addresses (hashed public keys) have an extra protection layer.
- No human readability — long hexadecimal strings are error-prone. ENS and other naming systems attempt to solve this.
Social Media Sentiment
On r/Bitcoin, public key and address concepts are common beginner questions. Experienced users consistently remind newcomers of the distinction between public keys and addresses. Discussions about quantum computing threats to ECDSA appear periodically on r/CryptoCurrency but are generally considered a distant concern. ENS names (human-readable Ethereum addresses) generate positive sentiment on r/ethereum as a usability improvement.
Last updated: 2026-04
Related Terms
Sources
- Diffie, W., & Hellman, M. E. (1976). New Directions in Cryptography. IEEE Transactions on Information Theory, 22(6), 644–654.
- Rivest, R. L., Shamir, A., & Adleman, L. (1978). A Method for Obtaining Digital Signatures and Public-Key Cryptosystems. Communications of the ACM, 21(2), 120–126.
- Johnson, D., Menezes, A., & Vanstone, S. (2001). The Elliptic Curve Digital Signature Algorithm (ECDSA). International Journal of Information Security, 1(1), 36–63.
- National Institute of Standards and Technology. (2023). FIPS 186-5: Digital Signature Standard (DSS). NIST.