From 4b8d3a9da9a1d2639dd5d3adeaad55f338ead612 Mon Sep 17 00:00:00 2001
From: Paul Selkirk <paul@psgd.org>
Date: Mon, 7 Jun 2021 14:13:23 -0400
Subject: Add mode bits for the various flavors of SHA-3, so that the software
 driver doesn't have to know that the internal block size is actually 1600
 bits. This involves having the "init" state zero-extend the block data, and
 having "next" only absorb the block bits for that mode.

---
 src/rtl/sha3.v | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 74 insertions(+), 12 deletions(-)

(limited to 'src/rtl/sha3.v')

diff --git a/src/rtl/sha3.v b/src/rtl/sha3.v
index a8b41bc..31b6465 100644
--- a/src/rtl/sha3.v
+++ b/src/rtl/sha3.v
@@ -44,20 +44,23 @@
 `define SHA3_NUM_ROUNDS         5'd24
 
 module sha3(    input wire          clk,
-                input wire          nreset,
-                input wire          w,
-                input wire [ 8:2]   addr,
-                input wire [32-1:0] din,
+                input wire 	     nreset,
+                input wire 	     w,
+                input wire [ 8:2]    addr,
+                input wire [32-1:0]  din,
                 output wire [32-1:0] dout,
-                input wire          init,
-                input wire          next,
-                output wire         ready);
+                input wire 	     init,
+                input wire 	     next,
+		input wire [ 1:0]    mode,
+                output wire 	     ready);
 
 
-   /* The SHA-3 algorithm really wants everything to be little-endian,
+   /*
+    * The SHA-3 algorithm really wants everything to be little-endian,
     * which is at odds with everything else in our system (including the
     * register interface to sha3_wrapper). Rather than trying to rewrite
-    * Bernd's beautiful code, we'll just byte-swap all I/O.
+    * Bernd's beautiful code, I'll isolate it in its own little-endian
+    * universe by byte-swapping all reads and writes.
     */
 
    reg [31:0]                       dout_swap;
@@ -193,10 +196,69 @@ module sha3(    input wire          clk,
 
            round <= round + 'd1;
 
-        end else if (init || next) begin
+        end else if (init) begin
+
+	   /*
+	    * I'd like to have something concise like this,
+	    * but the tools don't like it.
+
+           for (i = 0; i < blksize[mode]; i = i + 1)
+             st[i] <= st[i];
+
+           for (i < blksize[mode]; i < 25; i = i + 1)
+             st[i] <= 64'h0;
+
+	    */	   
+
+	   case (mode)
+	     0: begin
+		for (i = 0; i < 18; i = i + 1)
+		  st[i] <= blk[i];
+		for (i = 18; i < 25; i = i + 1)
+		  st[i] <= 64'h0;
+		end
+	     1: begin
+		for (i = 0; i < 17; i = i + 1)
+		  st[i] <= blk[i];
+		for (i = 17; i < 25; i = i + 1)
+		  st[i] <= 64'h0;
+		end
+	     2: begin
+		for (i = 0; i < 13; i = i + 1)
+		  st[i] <= blk[i];
+		for (i = 13; i < 25; i = i + 1)
+		  st[i] <= 64'h0;
+		end
+	     3: begin
+		for (i = 0; i < 9; i = i + 1)
+		  st[i] <= blk[i];
+		for (i = 9; i < 25; i = i + 1)
+		  st[i] <= 64'h0;
+		end
+	   endcase
 
-           for (i=0; i<25; i=i+1)
-             st[i] <= init ? blk[i] : st[i] ^ blk[i];   // init has priority over next
+           round <= 'd0;
+
+        end else if (next) begin
+
+	   case (mode)
+	     0: begin
+		for (i = 0; i < 18; i = i + 1)
+		  st[i] <= st[i] ^ blk[i];
+		end
+	     1: begin
+		for (i = 0; i < 17; i = i + 1)
+		  st[i] <= st[i] ^ blk[i];
+		end
+	     2: begin
+		for (i = 0; i < 13; i = i + 1)
+		  st[i] <= st[i] ^ blk[i];
+		end
+	     3: begin
+		for (i = 0; i < 9; i = i + 1)
+		  st[i] <= st[i] ^ blk[i];
+		end
+	   endcase
 
            round <= 'd0;
 
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