# 20159: Invalid Signature

Log Type: TWILIO

Log Level: ERROR

## Description

This error occurs when the JWT provided to the Twilio API has an invalid or mismatching signature.

### Possible causes

The public key referenced in the JWT does not match the actual private key used to sign the token.

### Possible solutions

* Ensure the private key used to sign the JWT corresponds to the public key identifier referenced in the token.
* If needed, validate the JWT's structure and signature using standard JWT tooling before retrying.

#### Additional resources

* [Access Tokens](/docs/iam/access-tokens)
* [API keys overview](/docs/iam/api-keys)
* [Public Key Client Validation Quickstart](/docs/iam/pkcv/quickstart)