[Cryptech-Commits] [core/pkey/ed25519] 05/08: * Removed unsed port to suppress warning during synthesis

[git at cryptech.is]

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meisterpaul1 at yandex.ru pushed a commit to branch master
in repository core/pkey/ed25519.

commit b9ea65597d951bba7602a93e0205342ab50e4d95
Author: Pavel V. Shatov (Meister) <meisterpaul1 at yandex.ru>
AuthorDate: Fri Nov 9 18:01:09 2018 +0300

     * Removed unsed port to suppress warning during synthesis
    
     * Made private key memory write-only (reading yields 0xDEADCE11), this
       prevents potential readout of the private key from the core by STM32
---
 rtl/ed25519_core_top.v | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/rtl/ed25519_core_top.v b/rtl/ed25519_core_top.v
index a217c75..6bd1c41 100644
--- a/rtl/ed25519_core_top.v
+++ b/rtl/ed25519_core_top.v
@@ -72,14 +72,15 @@ module ed25519_core_top
     wire        core_bram_qy_rw_wren;
 
     wire [31:0] core_bram_k_ro_dout;
-    wire [31:0] core_bram_qy_rw_dout_unused;
+//  wire [31:0] core_bram_qy_rw_dout_unused;
     
     wire [31:0] core_bram_qy_rw_din;
 
     assign user_bram_k_rw_din = bus_data_wr;
     assign user_bram_k_rw_wren = bus_cs && bus_we && (bus_addr_upper == BUS_ADDR_BANK_K);
     
-    bram_1rw_1ro_readfirst #
+    /* write-only memory here to prevent readback of the private key */
+    bram_1wo_1ro_readfirst #
     (
         .MEM_WIDTH(32),
         .MEM_ADDR_BITS(3)
@@ -90,6 +91,7 @@ module ed25519_core_top
         .b_addr(core_bram_k_ro_addr), .b_out(core_bram_k_ro_dout)
     );
 
+    /* read-write memory here */
     bram_1rw_1ro_readfirst #
     (
         .MEM_WIDTH(32),
@@ -98,7 +100,7 @@ module ed25519_core_top
     bram_qy
     (
         .clk(clk),
-        .a_addr(core_bram_qy_rw_addr), .a_out(core_bram_qy_rw_dout_unused), .a_wr(core_bram_qy_rw_wren), .a_in(core_bram_qy_rw_din),
+        .a_addr(core_bram_qy_rw_addr), .a_out(                    ), .a_wr(core_bram_qy_rw_wren), .a_in(core_bram_qy_rw_din),
         .b_addr(bus_addr_lower),       .b_out(user_bram_qy_ro_dout)
     );