Sign Protocol is an omni-chain attestation protocol that allows users to create, store, and verify attestations—digital assertions of facts or data—across multiple blockchain networks. The protocol leverages zero-knowledge cryptography, and digital signatures to ensure that these attestations are secure, verifiable, and tamper-resistant.Sign Protocol supports both on-chain and off-chain data storage, giving users flexibility in how and where their data is managed. On-chain storage provides strong guarantees such as censorship resistance and global consensus, while off-chain storage options like IPFS or Arweave offer efficient management of large datasets. The protocol also introduces the concept of hybrid attestations, where the attestation's metadata is stored on-chain while the bulk of the data resides off-chain.