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# SKAdTestError.Code.signatureInvalidKey

The public key isn’t a valid cryptographic key, in the testing environment.

```
case signatureInvalidKey
```

## Discussion

The public key that you provide in the [`validate(_:publicKey:)`](/documentation/StoreKitTest/SKAdTestSession/validate(_:publicKey:)) or [`validateImpression(parameters:publicKey:)`](/documentation/StoreKitTest/SKAdTestSession/validateImpression(parameters:publicKey:)) methods must be a key that uses Elliptic Curve Digital Signature Algorithm (ECDSA) with a prime256v1 curve. For more information about the key, see <doc://com.apple.documentation/documentation/StoreKit/registering-an-ad-network>.

---

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