Add poly1305 stage

ChaCha20_Poly1305_64/doc/notes.md

@@ -33,4 +33,34 @@ we need
 
 r\*r    = r^2
 r\*r^2  = r^3   r^2\*r^2 = r^4
-r^4\*r  = r^5   r^2\*r^4 = r^6  r^3\*r^4    = r^7   r^4\*r^4    = r^8
+r^4\*r  = r^5   r^2\*r^4 = r^6  r^3\*r^4    = r^7   r^4\*r^4    = r^8
+
+we can do all of these in parallel, so we 4 (n/2) multiply blocks that feed back
+on themselves, with some kind of FSM to control it. This can be done while another
+block is being hashed, but there will be a delay between when the key is ready from
+the chacha block and when the powers are ready, so there needs to be a fifo in between.
+
+
+Basically we have to wait until we see that the accumulator was written with our index.
+At reset though, the acumulator is unwritten? So we need to pretend that it was written
+
+Lets just write out what we want to happen:
+
+1. The index starts at 0. We accept new data, and send it through the pipeline
+2. We increment the index to 1.
+3. We accept new data and send it through the pipeline
+4. We increment the index to 2
+5. We need to wait until the index 0 is written before we can say we are ready
+6. If the index 1 is written then we still need to say we are ready though
+7. We can just use the 1 to indicate that is a valid write then?
+
+So in the shift register we just need to say whether it is a valid write or not,
+so always 1?
+
+But if we send in 0, then send in 1, then the current index will be 0
+and eventually the final index will always be 0. We need to store what
+the last written one is.
+
+We can just say the last written one was 2 I guess
+
+We also need an input that tells it to reset the accumulator