Protonlinked

Protonlinked is a privacy-preserving identity linkage protocol designed to securely connect multiple online accounts and verifiable credentials across services without exposing underlying personal data. It relies on user-controlled proofs that attest attributes such as age, education, or membership while keeping sensitive information off smaller service providers. The goal is to enable seamless cross-service trust without creating a central repository of identifiers.

Technically, Protonlinked uses decentralized identifiers (DIDs) and verifiable credentials (VCs) alongside privacy-preserving cryptography, including zero-knowledge proofs. Data that must remain private is kept off-chain, with a lightweight cryptographic commitment anchored on a public ledger to enable auditability and revocation.

The project originated in the early 2020s, emerging from a coalition of researchers and engineers who advocated self-sovereign identity and interoperable credentials. It is maintained as an open-source protocol with governance by a nonprofit foundation and participation from industry and academia.

Use cases include financial onboarding, healthcare data sharing, academic credential verification, and employment history attestation. Users can selectively disclose attributes, revoke permissions, and migrate credentials across services with verifiable proofs.

Reception has been mixed. Proponents emphasize improved privacy, user control, and reduced central risk, while critics point to regulatory uncertainty, interoperability challenges, and the potential for misconfigurations or key loss that could compromise security.

Related concepts include decentralized identifiers and verifiable credentials, self-sovereign identity, and privacy-preserving cryptography.