i have just released a very early draft of libseal (Segmented Encryption & Authentication Layer):

https://rad.ctrlc.hu/nodes/rad.ctrlc.hu/rad:z3wp7SxqLnD2XbwYZB8zFxTEvt4Jq

a construction that realizes random-access authenticated #encryption (raAE), it cuts a message into an indexed sequence of independently accessible, individually authenticated segments.

essentially this is very handy for data-at-rest & file encryption, u can do parallel en/decrypt, streaming & all kind of other things, while still have full integrity over the whole file.