ERC-5560

ERC-5560 is an Ethereum Improvement Proposal (EIP) that standardizes the generation and use of stealth addresses. A stealth address is a one-time-use public address generated by a sender for a specific recipient, allowing funds to be sent privately without any prior on-chain interaction. The recipient, who holds a private stealth meta-address, can scan the blockchain to discover and control funds sent to these ephemeral addresses. This mechanism decouples a user's persistent identity from their transaction history, significantly enhancing privacy for asset transfers on public blockchains.

The standard specifies a set of functions for key derivation and stealth address discovery. It uses elliptic curve cryptography, typically secp256k1, to generate a shared secret between the sender and recipient. The sender uses the recipient's publicly shared stealth meta-address to compute a unique stealth address for the transaction. Only the intended recipient, using their private viewing and spending keys, can compute the same shared secret and derive the corresponding private key for the newly created stealth address, thereby gaining control of the funds.

A core component of ERC-5560 is the stealth meta-address, which consists of a viewing public key and a spending public key. This meta-address is what users share to receive private payments. The standard also defines a standardized event, the StealthKey event, that wallets and indexers can emit to broadcast a user's stealth meta-address on-chain, facilitating discoverability without compromising the privacy of subsequent transactions. This creates a public directory for private interactions.

The primary use case for ERC-5560 is enabling private transfers of ERC-20 tokens, ERC-721 NFTs, and native ETH. It is particularly valuable for scenarios requiring financial privacy, such as payroll, donations, or confidential business transactions. By providing a non-interactive protocol, it solves the coordination problem present in earlier privacy schemes, as the recipient does not need to be online or have pre-published a receiving address for the transaction to succeed.

Implementation of ERC-5560 requires off-chain scanning by recipient wallets. Services known as stealth address providers or announcers can be built to index the blockchain, detect relevant StealthKey events and transactions, and notify users of incoming funds. The standard is extensible, allowing for different cryptographic schemes (like secp256r1) and integration with other privacy-enhancing technologies such as zero-knowledge proofs, forming a foundational layer for a more private Ethereum ecosystem.

ERC-5560 is an Ethereum Request for Comments (ERC) standard that defines a common interface for stealth address generation and management. Its primary purpose is to provide a standardized, non-custodial method for enhancing transaction privacy on Ethereum and compatible blockchains by allowing senders to create one-time addresses for recipients, obscuring the link between sender and receiver on the public ledger. The standard was formally proposed in 2022 by a group of developers and researchers, including Vitalik Buterin, Barry Whitehat, and others from the Ethereum Foundation and broader cryptography community.

The etymology of its name follows the established ERC numbering system, where '5560' is simply its sequential identifier in the registry of Ethereum improvement proposals. The conceptual origin, however, lies in the long-standing cryptographic concept of stealth addresses, which predate Ethereum. The proposal emerged from community discussions around scaling privacy solutions beyond mixers and zero-knowledge rollups, aiming to integrate a fundamental privacy primitive directly into the protocol layer. It builds upon earlier work on Diffie-Hellman key exchange and elliptic curve cryptography to create a scheme where only the intended recipient can compute the private key for a payment address they did not explicitly share.

The development of ERC-5560 was driven by the need for interoperability. Prior to its proposal, various projects implemented bespoke, incompatible stealth address mechanisms, creating fragmentation. By providing a canonical interface—specifying functions for generating stealth meta-addresses, deriving stealth addresses, and viewing keys—the standard allows wallets, explorers, and services to universally support private payments. This origin as a composability layer is quintessentially Ethereum, enabling innovation (like privacy-preserving DeFi or anonymous airdrops) to be built on a shared foundation rather than isolated in individual applications.

ERC-5560, also known as the Stealth Address Standard, works by enabling a sender to generate a one-time, private receiving address for a recipient without requiring prior interaction. The core mechanism relies on elliptic curve cryptography, specifically the secp256k1 curve used by Ethereum. A recipient publishes a stealth meta-address—a public key—to a registry. A sender uses this meta-address, along with a random secret, to compute a unique stealth address where funds are sent. Only the intended recipient, using their private key, can derive the corresponding private key for that stealth address and control the assets.

The standard specifies four core functions: generateStealthAddress, checkStealthAddress, computeStealthKey, and the event StealthAddress. The generateStealthAddress function is called by the sender; it takes the recipient's stealth meta-address and a random ephemeralPrivateKey to output a stealth address and associated viewTag for efficient discovery. The emitted StealthAddress event logs the stealth address, the sender's ephemeral public key, and the view tag, allowing the recipient—or designated stealth address providers—to scan the chain for transactions intended for them.

For a recipient to find their funds, they must scan the blockchain for StealthAddress events. Using the checkStealthAddress function, they can quickly filter events using the viewTag, a cryptographic hash that acts as a Bloom filter. For a matching event, the recipient then uses the computeStealthKey function with their private key and the ephemeral public key from the event to derive the private key for the stealth address. This process ensures that only the rightful owner can compute the key, as it depends on the Diffie-Hellman key exchange between the recipient's private key and the sender's ephemeral public key.

A critical component for usability is the stealth meta-address registry, which can be implemented as a smart contract or an off-chain directory. This registry allows users to associate a human-readable name or primary address with their stealth meta-address, making it easier for senders to find the correct public key. The standard is designed to be non-upgradeable and minimal, providing only the essential cryptographic primitives. Wallets and applications are expected to build user-friendly interfaces on top of this base layer to handle key generation, chain scanning, and transaction construction seamlessly.

ERC-5560's design has significant implications for privacy and scalability. By decoupling on-chain activity from identity, it breaks the heuristic links used in blockchain analysis. However, it introduces new challenges, such as the computational overhead for recipients to scan the chain and the need for reliable announcement channels for stealth meta-addresses. The standard is a foundational layer for privacy-preserving applications, enabling use cases like private airdrops, confidential payroll, and anonymous donations without requiring complex zero-knowledge proofs or mixing protocols.

The stealth address flow is a cryptographic protocol that enables private asset transfers on public blockchains by ensuring the recipient's primary address is never directly linked to a transaction. Instead, the sender uses the recipient's published stealth meta-address to generate a unique, one-time stealth address for the funds. Only the intended recipient, who holds the corresponding private keys, can discover and control this new address, making the payment opaque to external observers on the ledger.

The process begins with a user, the recipient, generating and publicly sharing a stealth meta-address derived from their private keys. A sender who wants to make a private payment uses this meta-address, along with a random secret (ephemeral private key), to compute a shared secret and subsequently the unique stealth address for the transaction. The funds are sent to this newly generated address, and the sender broadcasts a stealth meta-transaction or announcement containing cryptographic hints, enabling only the recipient to find the payment.

To discover incoming funds, the recipient or a service provider like an announcer scans the blockchain for these announcements. Using their private key and the ephemeral public key from the announcement, the recipient can independently compute the same shared secret and derive the stealth address where the funds reside. This allows them to generate the corresponding private key for that address and take custody of the assets, completing the private transfer loop without any prior interaction with the sender.

This mechanism, formalized in ERC-5560: Stealth Addresses for Ethereum, provides transaction privacy by breaking the on-chain link between payer and payee. Unlike mixing services, it is a non-interactive, native protocol that does not require a trusted third party or batching of transactions. Its core components include the Diffie-Hellman key exchange, elliptic curve cryptography, and a standardized announcement format to ensure interoperability across wallets and applications.

Practical implementation requires infrastructure like announcement registries (e.g., a smart contract) where senders post hints, and scanning services that help recipients discover transactions. While it provides strong privacy for recipients, it introduces challenges such as gas costs for announcements and the computational load of scanning. This flow is foundational for private airdrops, confidential payments, and enhancing overall financial privacy on transparent networks like Ethereum.