aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--src/rtl/avalanche_entropy.v380
1 files changed, 380 insertions, 0 deletions
diff --git a/src/rtl/avalanche_entropy.v b/src/rtl/avalanche_entropy.v
new file mode 100644
index 0000000..a7a23b1
--- /dev/null
+++ b/src/rtl/avalanche_entropy.v
@@ -0,0 +1,380 @@
+//======================================================================
+//
+// avalanche_entropy.v
+// -------------------
+// Top level wrapper of the entropy provider core based on an external
+// avalanche noise based source. (or any other source that can
+// toggle a single bit input).
+//
+// Currently the design consists of a free running counter. At every
+// positive flank detected the LSB of the counter is pushed into
+// a 32bit shift register.
+//
+//
+// Author: Joachim Strombergson
+// Copyright (c) 2013, 2014, Secworks Sweden AB
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or
+// without modification, are permitted provided that the following
+// conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright
+// notice, this list of conditions and the following disclaimer in
+// the documentation and/or other materials provided with the
+// distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+// ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//======================================================================
+
+module avalanche_entropy(
+ input wire clk,
+ input wire reset_n,
+
+ input wire noise,
+
+ input wire cs,
+ input wire we,
+ input wire [7 : 0] address,
+ input wire [31 : 0] write_data,
+ output wire [31 : 0] read_data,
+ output wire error,
+
+ input wire discard,
+ input wire test_mode,
+ output wire security_error,
+
+ output wire entropy_enabled,
+ output wire [31 : 0] entropy_data,
+ output wire entropy_valid,
+ input wire entropy_ack,
+
+ output wire [7 : 0] debug,
+ input wire debug_update
+ );
+
+
+ //----------------------------------------------------------------
+ // Internal constant and parameter definitions.
+ //----------------------------------------------------------------
+ parameter ADDR_CTRL = 8'h10;
+ parameter CTRL_ENABLE_BIT = 0;
+
+ parameter ADDR_STATUS = 8'h11;
+ parameter ADDR_ENTROPY = 8'h20;
+ parameter ADDR_DELTA = 8'h30;
+
+ parameter DEBUG_DELAY = 32'h002c4b40;
+
+
+ //----------------------------------------------------------------
+ // Registers including update variables and write enable.
+ //----------------------------------------------------------------
+ reg noise_sample0_reg;
+ reg noise_sample_reg;
+
+ reg flank0_reg;
+ reg flank1_reg;
+
+ reg entropy_bit_reg;
+
+ reg [31 : 0] entropy_reg;
+ reg [31 : 0] entropy_new;
+ reg entropy_we;
+
+ reg entropy_syn_reg;
+ reg entropy_syn_new;
+
+ reg [5 : 0] bit_ctr_reg;
+ reg [5 : 0] bit_ctr_new;
+ reg bit_ctr_inc;
+ reg bit_ctr_we;
+
+ reg [31 : 0] cycle_ctr_reg;
+ reg [31 : 0] cycle_ctr_new;
+
+ reg [31 : 0] delta_reg;
+ reg delta_we;
+
+ reg enable_reg;
+ reg enable_new;
+ reg enable_we;
+
+ reg [31 : 0] debug_delay_ctr_reg;
+ reg [31 : 0] debug_delay_ctr_new;
+ reg debug_delay_ctr_we;
+
+ reg [7 : 0] debug_reg;
+ reg debug_we;
+
+ reg debug_update_reg;
+
+
+ //----------------------------------------------------------------
+ // Wires.
+ //----------------------------------------------------------------
+ reg [31 : 0] tmp_read_data;
+ reg tmp_error;
+
+
+ //----------------------------------------------------------------
+ // Concurrent connectivity for ports etc.
+ //----------------------------------------------------------------
+ assign read_data = tmp_read_data;
+ assign error = tmp_error;
+ assign security_error = 0;
+
+ assign entropy_valid = entropy_syn_reg;
+ assign entropy_data = entropy_reg;
+ assign entropy_enabled = enable_reg;
+
+ assign debug = debug_reg;
+
+
+ //----------------------------------------------------------------
+ // reg_update
+ //----------------------------------------------------------------
+ always @ (posedge clk or negedge reset_n)
+ begin
+ if (!reset_n)
+ begin
+ noise_sample0_reg <= 1'b0;
+ noise_sample_reg <= 1'b0;
+ flank0_reg <= 1'b0;
+ flank1_reg <= 1'b0;
+ entropy_syn_reg <= 1'b0;
+ entropy_reg <= 32'h00000000;
+ entropy_bit_reg <= 1'b0;
+ bit_ctr_reg <= 6'h00;
+ cycle_ctr_reg <= 32'h00000000;
+ delta_reg <= 32'h00000000;
+ enable_reg <= 1;
+ debug_delay_ctr_reg <= 32'h00000000;
+ debug_reg <= 8'h00;
+ debug_update_reg <= 0;
+ end
+ else
+ begin
+ noise_sample0_reg <= noise;
+ noise_sample_reg <= noise_sample0_reg;
+
+ flank0_reg <= noise_sample_reg;
+ flank1_reg <= flank0_reg;
+
+ entropy_syn_reg <= entropy_syn_new;
+ entropy_bit_reg <= ~entropy_bit_reg;
+ cycle_ctr_reg <= cycle_ctr_new;
+
+ debug_update_reg <= debug_update;
+
+ if (enable_we)
+ begin
+ enable_reg <= enable_new;
+ end
+
+ if (delta_we)
+ begin
+ delta_reg <= cycle_ctr_reg;
+ end
+
+ if (bit_ctr_we)
+ begin
+ bit_ctr_reg <= bit_ctr_new;
+ end
+
+ if (entropy_we)
+ begin
+ entropy_reg <= entropy_new;
+ end
+
+ if (debug_delay_ctr_we)
+ begin
+ debug_delay_ctr_reg <= debug_delay_ctr_new;
+ end
+
+ if (debug_we)
+ begin
+ debug_reg <= entropy_reg[7 : 0];
+ end
+ end
+ end // reg_update
+
+
+ //----------------------------------------------------------------
+ // debug_out
+ //
+ // Logic that updates the debug port.
+ //----------------------------------------------------------------
+ always @*
+ begin : debug_out
+ debug_delay_ctr_new = 8'h00000000;
+ debug_delay_ctr_we = 0;
+ debug_we = 0;
+
+ if (debug_update_reg)
+ begin
+ debug_delay_ctr_new = debug_delay_ctr_reg + 1'b1;
+ debug_delay_ctr_we = 1;
+ end
+
+ if (debug_delay_ctr_reg == DEBUG_DELAY)
+ begin
+ debug_delay_ctr_new = 8'h00000000;
+ debug_delay_ctr_we = 1;
+ debug_we = 1;
+ end
+ end
+
+
+ //----------------------------------------------------------------
+ // entropy_collect
+ //
+ // We collect entropy by adding the current state of the
+ // entropy bit register the entropy shift register every time
+ // we detect a positive flank in the noise source.
+ //----------------------------------------------------------------
+ always @*
+ begin : entropy_collect
+ entropy_new = 32'h00000000;
+ entropy_we = 1'b0;
+ bit_ctr_inc = 1'b0;
+
+ if ((flank0_reg) && (!flank1_reg))
+ begin
+ entropy_new = {entropy_reg[30 : 0], entropy_bit_reg};
+ entropy_we = 1'b1;
+ bit_ctr_inc = 1'b1;
+ end
+ end // entropy_collect
+
+
+ //----------------------------------------------------------------
+ // delta_logic
+ //
+ // The logic implements the delta time measuerment system.
+ //----------------------------------------------------------------
+ always @*
+ begin : delta_logic
+ cycle_ctr_new = cycle_ctr_reg + 1'b1;
+ delta_we = 1'b0;
+
+ if ((flank0_reg) && (!flank1_reg))
+ begin
+ cycle_ctr_new = 32'h00000000;
+ delta_we = 1'b1;
+ end
+ end // delta_logic
+
+
+ //----------------------------------------------------------------
+ // entropy_ack_logic
+ //
+ // The logic needed to handle detection that entropy has been
+ // read and ensure that we collect more than 32 entropy
+ // bits beforeproviding more entropy.
+ //----------------------------------------------------------------
+ always @*
+ begin : entropy_ack_logic
+ bit_ctr_new = 6'h00;
+ bit_ctr_we = 1'b0;
+ entropy_syn_new = 1'b0;
+
+ if (bit_ctr_reg == 6'h20)
+ begin
+ entropy_syn_new = 1'b1;
+ end
+
+ if ((bit_ctr_inc) && (bit_ctr_reg < 6'h20))
+ begin
+ bit_ctr_new = bit_ctr_reg + 1'b1;
+ bit_ctr_we = 1'b1;
+ end
+ else if (entropy_ack)
+ begin
+ bit_ctr_new = 6'h00;
+ bit_ctr_we = 1'b1;
+ end
+ end // entropy_ack_logic
+
+
+ //----------------------------------------------------------------
+ // api_logic
+ //----------------------------------------------------------------
+ always @*
+ begin : api_logic
+ tmp_read_data = 32'h00000000;
+ tmp_error = 1'b0;
+ enable_new = 0;
+ enable_we = 0;
+
+ if (cs)
+ begin
+ if (we)
+ begin
+ case (address)
+ // Write operations.
+ ADDR_CTRL:
+ begin
+ enable_new = write_data[CTRL_ENABLE_BIT];
+ enable_we = 1;
+ end
+
+ default:
+ begin
+ tmp_error = 1;
+ end
+ endcase // case (address)
+ end // if (we)
+
+ else
+ begin
+ case (address)
+ ADDR_CTRL:
+ begin
+ tmp_read_data = {31'h00000000, enable_reg};
+ end
+
+ ADDR_STATUS:
+ begin
+ tmp_read_data = {31'h00000000, entropy_syn_reg};
+ end
+
+ ADDR_ENTROPY:
+ begin
+ tmp_read_data = entropy_reg;
+ end
+
+ ADDR_DELTA:
+ begin
+ tmp_read_data = delta_reg;
+ end
+
+ default:
+ begin
+ tmp_error = 1;
+ end
+ endcase // case (address)
+ end // else: !if(we)
+ end // if (cs)
+ end // api_logic
+
+endmodule // avalanche_entropy
+
+//======================================================================
+// EOF avalanche_entropy.v
+//======================================================================