The error message "error:0906D06C:PEM routines:PEM_read_bio:no start line" usually indicates an issue with the format of the PEM-encoded data being used in Node.js when working with JWT (JSON Web Tokens). This error often occurs when trying to decode a JWT using an invalid or incorrectly formatted public or private key.

To resolve this issue, make sure to use the correct PEM-encoded data when working with JWTs. Here are some common scenarios that can cause this error and their corresponding solutions:

  1. Public Key is Missing or Incorrect: If you are trying to verify a JWT using a public key, ensure that you have the correct PEM-encoded public key. The public key should start with "-----BEGIN PUBLIC KEY-----" and end with "-----END PUBLIC KEY-----". Make sure there are no leading or trailing white spaces, newlines, or other characters outside the "-----BEGIN" and "-----END" lines.

  2. Private Key is Missing or Incorrect: If you are trying to sign or decode a JWT using a private key, ensure that you have the correct PEM-encoded private key. The private key should start with "-----BEGIN PRIVATE KEY-----" and end with "-----END PRIVATE KEY-----". Again, ensure there are no additional characters outside these lines.

  3. PEM-Encoded Key is Not Complete: Double-check that the PEM-encoded key is complete and not cut off. Sometimes, copying the key from a source might lead to missing characters, causing the error. Make sure the key is not truncated or altered during copying.

  4. Environment Variable Issues: If you are storing the PEM-encoded key as an environment variable, check that the variable is set correctly and is not missing any characters.

  5. File Encoding Issues: If the PEM-encoded key is stored in a file, verify that the file is correctly encoded. Ensure it uses the appropriate line endings for your operating system (e.g., LF for Unix-like systems, CRLF for Windows).

  6. Base64 Encoding: Sometimes, PEM-encoded keys are Base64-encoded for storage or transport. If that's the case, make sure to decode the Base64-encoded key before using it with JWT libraries.

Ensure that you are using the correct PEM-encoded data, and verify that the keys match the use case (public key for verification, private key for signing/decoding). By addressing any of the above potential issues, you should be able to resolve the "error:0906D06C:PEM routines:PEM_read_bio:no start line" error when working with JWT in Node.js.

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