i haven't actually written code to upload profile images recently, but what
i would try is the following (and i apologise if i'm slightly incorrect as
i'm doing this from memory):
> 1. What all parameters should be part of the signature base string?
of course, the request type and URL comprise the block that needs to be
2. Where should the parameters and the signature be placed in the
> request stream?
the authorization header would be the best place to stick it.
> 3. How should the file data be sent?
multipart/form-data, i believe.
Twitter Platform Team