It is not possible to ship binary over XML. Regardless of encoding used, XML rigidly forbids the bytes corresponding to non-whitespace ASCII chars below 32: http://www.w3.org/TR/2008/REC-xml-20081126/#charsets This makes arbitrary binary impossible. You have to base64 encode it or something.

Not entirely relevant to your point, but worth bringing up. (XML doesn't ever mangle binaries, because it simply forbids them.)