I am following this document, but making the request in bash:

https://developer.box.com/guides/authentication/jwt/without-sdk/

The error I receive is: 

{"error":"invalid_grant","error_description":"Empty algorithm"}

This error is not documented ( I looked here - https://developer.box.com/guides/api-calls/permissions-and-errors/common-errors/)

Here is my bash script, which generates the assertion and make the request to get the access token:

https://github.com/BarakBD-Globality/box-oauth-uploader/blob/request-token-using-private-key/jwt-encode.sh

Please help.