MATTR MATTR Portage CryptID This document describes the BBS Signature scheme, a secure, multi- message digital signature protocol, supporting proving knowledge of a signature while selectively disclosing any subset of the signed messages. Concretely, the scheme allows for signing multiple messages whilst producing a single, constant size, digital signature. Additionally, the possessor of a BBS signatures is able to create zero-knowledge, proofs of knowledge of a signature, while selectively disclosing subsets of the signed messages. Being zero-knowledge, the BBS proofs do not reveal any information about the undisclosed messages or the signature itself, while at the same time, guaranteeing the authenticity and integrity of the disclosed messages.