# CTO, MATTR; editor of OpenID4VCI and BBS Signatures

Source: https://startwithidentity.com/experts/tobias-looker/
Last updated: 2026-09-20
License: content by Start with Identity. Cite the source URL.

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## Bio

Tobias Looker is CTO of MATTR, an editor of OpenID for Verifiable Credential Issuance, and a co-editor of the BBS Signature scheme at the IRTF Crypto Forum Research Group. Much of the BBS work ran through the Decentralized Identity Foundation's applied cryptography group.

Profile built from public IETF, OpenID Foundation, and company records.

## Where their work shows up

Selective disclosure has two competing mechanisms. Salted-hash schemes such as SD-JWT hide unrevealed fields but still expose a fixed signature, so repeated presentations are linkable. BBS signatures allow a holder to derive a fresh, unlinkable proof for each presentation, which is what unlinkable credential use actually requires. Which one a scheme picks determines whether a verifier and an issuer can collude to track a person. See [verifiable credentials](https://startwithidentity.com/standards/verifiable-credentials/), [OpenID4VC](https://startwithidentity.com/standards/openid4vc/), and the [MATTR profile](https://startwithidentity.com/vendors/decentralized-identity/mattr/).