Sign Protocol pioneered on-chain attestation with a unified schema across chains. H33-74 makes the evidence chain-portable instead of multi-chain.
Sign Protocol provides a chain-agnostic-in-marketing-sense attestation primitive. Schemas, attestations, and revocations live on chain, with cross-chain registries letting attestations be referenced from multiple EVM chains. Sign's design center is on-chain composability of attestations across chains.
Both projects acknowledge that single-chain attestation is too narrow. Both produce structured attestations rather than just timestamps. Both have schema concepts for attestation types. Both support multiple chains.
Sign Protocol is great when on-chain composability of attestations across EVM chains is the value being delivered, when attestation consumers are smart contracts, and when the operator is comfortable with pre-quantum signatures for the audit horizon.
H33-74 is great when attestation consumers are auditors and regulators outside the EVM ecosystem. When the receipt needs to survive any single chain's deprecation or compromise. When post-quantum survivability matters. When the audit horizon extends past chain-ecosystem lifetimes.
Chain portability separates evidence from the infrastructure that produced it.
Chain Portability What Gets Preserved