Hot answers tagged authenticated-encryption
What you're describing is pretty similar to the SIV block cipher mode. It also uses a deterministic function of the message to derive the nonce for CTR encryption. Under some pretty widely accepted assumptions about HMAC-SHA256 this is a perfectly fine way of achieving deterministic authenticated encryption. It doesn't meet IND-CPA (as you pointed out) but ...
Only top voted, non community-wiki answers of a minimum length are eligible