ERC-8376 Impersonation Extension Schema v0.1

The reference extension schema for PATTERN_IMPERSONATION, published at a stable URI as the Extension Signals section of ERC-8376 requires.

PATTERN_IMPERSONATION cannot be scored from the base vector. A deployer may retain no supply, lock liquidity, hold no privileged powers, and read clean on all twelve signals, because the abuse is entirely in the identity claim. It is the reason extension schemas exist and is specified here as their reference.

Schema keccak256("erc.launch.schema.impersonation"), version 1:

Field	Type	Units	Definition	Polarity	Threshold
symbolCollision	uint16	bitmask	Established tokens sharing this symbol on this chain, by class: 0x0001 any, 0x0002 one of greater age, 0x0004 one of greater liquidity	Adverse	any bit set
nameSimilarity	uint16	bps	Similarity of the token name to that of an established token, by a published measure the detector MUST name in evidenceURI	Adverse	8000
metadataReuse	uint16	bps	Share of launch metadata, including logo and stated URIs, identical to an established project’s	Adverse	5000

Weights: symbolCollision 40, nameSimilarity 30, metadataReuse 20, priorUpheldClaims 10.

“Established” MUST be defined by the deployment and published with the profile. Age and liquidity are both reasonable bases; neither is mandated, because the right threshold differs by chain and venue.

Both symbolCollision and nameSimilarity MUST be computed over normalized strings, since the attack this pattern describes is carried in the encoding rather than in the glyphs a reader sees. A detector MUST apply Unicode Normalization Form KC, MUST strip characters with no visual width, including zero-width space, zero-width non-joiner, zero-width joiner and the byte order mark, and MUST fold confusable characters to a skeleton by a published mapping, for which the Unicode consortium’s confusables data is RECOMMENDED. A symbol rendering identically to an established token’s while differing in code points MUST set the same bits in symbolCollision as an exact match, and a detector MUST report in evidenceURI the normalization and confusable mapping it applied, with their versions.

A detector MUST publish the definition of the measure it used, in enough detail for a third party to reproduce the figure from the same two strings. The definition is what makes the reading checkable and the bond behind it enforceable; who supplies the measure is not part of the report.