CRC downloaded files over 3G not match

Some cell providers compress files, my case Vodafone(Spain)

As a result we have doubly compressed files whose crc does not match the source file.

I've seen two solutions: 
1. use https instead of http 
2. Use non-transform 

For me, it is me with option 2.

The idea is to add a no-transform cache-control HTTP header to request.
This disallow the server from making this kind of change.

http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9.5