ok; in my case i was confused by the way pycrypto handles ivs for ctr mode (it ignores the iv and expects an explicit offset or prefix to the counter). so init

ok; in my case i was confused by the way pycrypto handles ivs for ctr mode (it ignores the iv and expects an explicit offset or prefix to the counter). so initially i had the same encryption every time. but anyway, ignoring that red herring, if you have the time, confirmation that it seems to do what you described would be appreciated... [edit: fwiw, other concerns i have include: is there any reason why hmac shouldn't use the same key as the main cipher; is it better to use a random counter offset or a smaller counter and a prefix / nonce?]