amazon s3 - FineUploader - Error on multi-part upload to S3 -

i using fineuploader upload s3. have working including deletes. however, when upload larger files broken multi-part uploads, following error in console (debugging turned on):

specific problem detected initiating multipart upload request 0: 'the request signature calculated not match signature provided. check key , signing method.'.  

can point me in right direction should check settings, or additional info might need?

since haven't included specific setup, code, or failing request, best guess server isn't returning proper signature response uploads made s3 rest api (which used larger files). you'll need review procedure generating response type of signature request.

here's relevant section fine uploader's s3 documentation:

fine uploader s3 uses amazon s3’s rest api initiate, upload, complete, , abort multipart uploads. rest api handles authentication signing canonically formatted headers. signing need implement server-side. server needs authenticate , supported chunked uploads direct amazon s3 sign string representing headers of request fine uploader sends s3. string found in payload of signature request:

{ "headers": /* string sign */ }

the presence of property indicates sever is, in fact, request sign rest/multipart request , not policy document.

this signature headers string differs policy document signature. should not base64 encode headers string before signing it. must do, server-side, generate hmac sha1 signature of string using aws secret key , base64 encode result. server should respond following in body of ‘application/json’ response:

{ "signature": /* signed headers string */ }