Stream cipher with an additional integrity stream? I want to use a stream cipher to encrypt a continuous bitstream. Additional to that, I want to generate an additional stream to guarantee the integrity of the ciphertext.


stream a: ciphertext.  
stream b: integrity check on stream a.


I am aware of authenticated encryption where the MAC can be accumulated and sent. I want to avoid that.

Is it possible to do this by encrypting the same plaintext using a different algorithm, key or iv? Will that actually protect against say bit-flip attacks? Does it cause any vulnerabilities?

Is there a better (preferably cheaper) way to do this?

Note that this has to be done in hardware and I am extremely limited on energy so I can't add any sort of control logic.
Break your stream into chunks.  Use an AEAD for each chunk using the chunk sequence number as a nonce.  Anything else is going to have at best the same effect, but will be convoluted, full of holes for the first umpteen drafts, difficult to implement, and nonstandard, and will have the effect of making cryptographers look at you like you have three heads.

Or, use a system that was already designed to do this (in particular, STREAM).