# identity-signature-key

> A successful history passes a known identity point to the pinned Schnorr verifier.

Canonical: https://nightshade.dicksonwu.xyz/rules/identity-signature-key.html
Release: Nightshade 0.1.1 (v0.1.1)

| Field | Value |
| --- | --- |
| Rule ID | `identity-signature-key` |
| Severity | medium |
| Confidence | high |
| Maturity | experimental |
| Selection | Audit default |
| Policy intent | not required |
| Default enabled | yes |
| Category | Audit-default ordinary rules |
| Engine facts used | resolved-calls, constants, successful-signature-calls |
| Release | v0.1.1 |

## Selection and scope

Selected by the default audit profile, so an ordinary scan runs it.

```sh
./.nightshade/node_modules/.bin/nightshade ./contracts --detectors identity-signature-key
./.nightshade/node_modules/.bin/nightshade detector show identity-signature-key
```

The first command runs only this rule; `--detectors` takes a comma-separated list. The second prints the rule's metadata from your installed version.

Severity is review priority. It does not express exploitability or impact. Confidence is detector metadata, not a probability. All built-in rules are experimental.

Compiler scope: the engine supports the pinned profiles 0.28.0, 0.29.0, 0.30.0, 0.31.1, 0.33.0-rc.2, 0.34.0, 0.35.0-rc.1 and 0.35.0, with ZKIR2 by default. Support for this rule can be narrower; the rule documentation below states any narrower scope.

## Corpus checks

Synthetic corpus checks for this rule in the 0.1.1 proof run. A check counts only with compiler acceptance and complete analysis.

| Positive detected | Corrected quiet | Lookalike quiet | Other negative quiet | Incomplete |
| ---: | ---: | ---: | ---: | ---: |
| 1/4 | 4/4 | 4/4 | 0/0 | 0 |

Deviations recorded for this rule:

| Case | Kind | Expected to observed lines | Issue |
| --- | --- | --- | --- |
| synthetic-regressions.json / identity-signature-key-71 | positive | [6] to [] | miss, exact expectation mismatch |
| synthetic-regressions.json / identity-signature-key-71 | lookalike | [7] to [] | exact expectation mismatch |
| synthetic-regressions.json / identity-signature-key-96 | positive | [4,7] to [] | miss, exact expectation mismatch |
| synthetic-regressions.json / identity-signature-key-96 | lookalike | [5,9] to [] | exact expectation mismatch |
| synthetic-regressions.json / identity-signature-key-97 | positive | [10,13] to [] | miss, exact expectation mismatch |
| synthetic-regressions.json / identity-signature-key-97 | lookalike | [11,15] to [] | exact expectation mismatch |

These are behavior checks on synthetic fixtures, not a precision or recall estimate. See [evaluation](https://nightshade.dicksonwu.xyz/evaluation.md#synthetic-corpus).

## Rule documentation

From https://github.com/DicksonWu654/nightshade/blob/v0.1.1/docs/detectors/identity-signature-key.md at v0.1.1.

Availability: **default-on**; severity **medium**, confidence **high**.
No application policy is needed. This rule reports only a statically known identity
key on a modeled successful history, not every unconstrained verification key.

### Example and scenario

```compact
assert(jubjubSchnorrVerify<1>(message, signature, default<JubjubPoint>), "signature");
round.increment(1);
```

An identity verification key does not supply the intended signer authentication.
The known-key diagnosis is factual; the analyzer does not construct a signature,
prove exploitability, or infer a deployed application's intended signer.
### Recommendation

Reject the identity key and bind the verification key to the intended trusted
signer. A nonidentity check alone does not establish trusted ownership or complete
key validity. The pinned stable 0.35.0 and 0.35.0-rc.1 standard-library verifiers
reject identity keys internally; profile support is a ZKIR2 subset, and upgrades
need compatibility review.

### Evidence and known false positives

Canonical resolved stdlib calls retain separate key operands on successful
histories. Aliases, helpers, known zero multiplication and caller equality
refinements are supported. Rejected histories and same-named application circuits
are quiet. No new observation is enabled in projects without the canonical verifier.
Observation exhaustion remains explicitly incomplete.

## Suppress a match

If a match is intentional, suppress it on the line before with the exact rule ID and a reason of at least eight characters:

```compact
// nightshade-disable-next-line identity-signature-key -- Reason this match is intentional
```

Diagnostics cannot be suppressed, and an unmatched directive for a selected rule makes analysis incomplete. See [configuration](https://nightshade.dicksonwu.xyz/configuration.md#suppress-an-intentional-match) for fingerprint suppressions and baselines.

## References

- [Rule source document at v0.1.1](https://github.com/DicksonWu654/nightshade/blob/v0.1.1/docs/detectors/identity-signature-key.md)
- [Catalog entry in rules.json](https://nightshade.dicksonwu.xyz/rules.json)
- [All rules](https://nightshade.dicksonwu.xyz/rules.md#audit-default-ordinary-rules)
- [Limitations](https://nightshade.dicksonwu.xyz/limitations.md)