Subversion Repositories neorv32

-- #################################################################################################

-- # << NEORV32 - True Random Number Generator (TRNG) >>                                           #

-- # ********************************************************************************************* #

-- # This unit implements a true random number generator which uses several GARO chain as entropy  #

-- # source. The outputs of all chains are XORed and de-biased using a John von Neumann randomness #

-- # extractor. The de-biased signal is further processed by a simple LFSR for improved whitening. #

-- #                                                                                               #

-- # Sources:                                                                                      #

-- #  - Von Neumann De-Biasing: "Iterating Von Neumann's Post-Processing under Hardware            #

-- #    Constraints" by Vladimir Rozic, Bohan Yang, Wim Dehaene and Ingrid Verbauwhede, 2016       #

-- # ********************************************************************************************* #

-- # BSD 3-Clause License                                                                          #

-- #                                                                                               #

-- # Copyright (c) 2020, Stephan Nolting. 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.                                                            #

-- #                                                                                               #

-- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #

-- #    endorse or promote products derived from this software without specific prior written      #

-- #    permission.                                                                                #

-- #                                                                                               #

-- # 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 HOLDER 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.                                                            #

-- # ********************************************************************************************* #

-- # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

-- #################################################################################################

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

library neorv32;

use neorv32.neorv32_package.all;

entity neorv32_trng is

  port (

    -- host access --

    clk_i  : in  std_ulogic; -- global clock line

    addr_i : in  std_ulogic_vector(31 downto 0); -- address

    rden_i : in  std_ulogic; -- read enable

    wren_i : in  std_ulogic; -- write enable

    data_i : in  std_ulogic_vector(31 downto 0); -- data in

    data_o : out std_ulogic_vector(31 downto 0); -- data out

    ack_o  : out std_ulogic  -- transfer acknowledge

  );

end neorv32_trng;

architecture neorv32_trng_rtl of neorv32_trng is

  -- advanced configuration --------------------------------------------------------------------------------

  constant num_inv_c   : natural := 15; -- length of GARO inverter chain (default=15, has to be odd)

  constant num_garos_c : natural := 2; -- number of GARO elements (default=2)

  constant lfsr_taps_c : std_ulogic_vector(7 downto 0) := "10111000"; -- Fibonacci post-processing LFSR feedback taps

  constant lfsr_en_c   : boolean := true; -- use LFSR-based post-processing

  type tap_mask_t is array (0 to num_garos_c-1) of std_ulogic_vector(num_inv_c-2 downto 0);

  constant tap_mask : tap_mask_t := ( -- GARO tap masks, sum of set bits has to be even

    "11110000000000",

    "00000011000000"

  );

  -- -------------------------------------------------------------------------------------------------------

  -- control register bits --

  constant ctrl_data_lsb_c   : natural :=  0; -- r/-: Random data bit LSB

  constant ctrl_data_msb_c   : natural :=  7; -- r/-: Random data bit MSB

  constant ctrl_data_valid_c : natural := 15; -- r/-: Output data valid

  constant ctrl_err_zero_c   : natural := 16; -- r/-: stuck at 0 error

  constant ctrl_err_one_c    : natural := 17; -- r/-: stuck at 1 error

  constant ctrl_en_c         : natural := 31; -- r/w: TRNG enable

  -- IO space: module base address --

  constant hi_abb_c : natural := index_size_f(io_size_c)-1; -- high address boundary bit

  constant lo_abb_c : natural := index_size_f(trng_size_c); -- low address boundary bit

  -- Component: GARO Element --

  component neorv32_trng_garo_element

    generic (

      NUM_INV : natural := 16 -- number of inverters in chain

    );

    port (

      clk_i    : in  std_ulogic;

      enable_i : in  std_ulogic;

      enable_o : out std_ulogic;

      mask_i   : in  std_ulogic_vector(NUM_INV-2 downto 0);

      data_o   : out std_ulogic;

      error0_o : out std_ulogic;

      error1_o : out std_ulogic

    );

  end component;

  -- access control --

  signal acc_en : std_ulogic; -- module access enable

  signal addr   : std_ulogic_vector(31 downto 0); -- access address

  signal wren   : std_ulogic; -- full word write enable

  signal rden   : std_ulogic; -- read enable

  -- garo array --

  signal garo_en_in    : std_ulogic_vector(num_garos_c-1 downto 0);

  signal garo_en_out   : std_ulogic_vector(num_garos_c-1 downto 0);

  signal garo_data     : std_ulogic_vector(num_garos_c-1 downto 0);

  signal garo_err_zero : std_ulogic_vector(num_garos_c-1 downto 0);

  signal garo_err_one  : std_ulogic_vector(num_garos_c-1 downto 0);

  signal garo_res      : std_ulogic;

  signal garo_err0     : std_ulogic;

  signal garo_err1     : std_ulogic;

  -- de-biasing --

  signal db_data     : std_ulogic_vector(2 downto 0);

  signal db_state    : std_ulogic; -- process de-biasing every second cycle

  signal rnd_valid   : std_ulogic;

  signal rnd_data    : std_ulogic;

  -- processing core --

  signal rnd_enable : std_ulogic;

  signal rnd_cnt    : std_ulogic_vector(3 downto 0);

  signal rnd_sreg   : std_ulogic_vector(7 downto 0);

  signal rnd_output : std_ulogic_vector(7 downto 0);

  signal rnd_ready  : std_ulogic;

  -- health check --

  signal rnd_error_zero : std_ulogic; -- stuck at zero

  signal rnd_error_one  : std_ulogic; -- stuck at one

begin

  -- Access Control -------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  acc_en <= '1' when (addr_i(hi_abb_c downto lo_abb_c) = trng_base_c(hi_abb_c downto lo_abb_c)) else '0';

  addr   <= trng_base_c(31 downto lo_abb_c) & addr_i(lo_abb_c-1 downto 2) & "00"; -- word aligned

  wren   <= acc_en and wren_i;

  rden   <= acc_en and rden_i;

  -- Read/Write Access ----------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  rw_access: process(clk_i)

  begin

    if rising_edge(clk_i) then

      ack_o <= acc_en and (rden_i or wren_i);

      -- write access --

      if (wren = '1') then

        rnd_enable <= data_i(ctrl_en_c);

      end if;

      -- read access --

      data_o <= (others => '0');

      if (rden = '1') then

        data_o(ctrl_data_msb_c downto ctrl_data_lsb_c) <= rnd_output;

        data_o(ctrl_data_valid_c) <= rnd_ready;

        data_o(ctrl_err_zero_c)   <= rnd_error_zero;

        data_o(ctrl_err_one_c)    <= rnd_error_one;

        data_o(ctrl_en_c)         <= rnd_enable;

      end if;

    end if;

  end process rw_access;

  -- Entropy Source -------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  neorv32_trng_garo_element_inst:

  for i in 0 to num_garos_c-1 generate

    neorv32_trng_garo_element_inst_i: neorv32_trng_garo_element

    generic map (

      NUM_INV => num_inv_c -- number of inverters in chain

    )

    port map (

      clk_i    => clk_i,

      enable_i => garo_en_in(i),

      enable_o => garo_en_out(i),

      mask_i   => tap_mask(i),

      data_o   => garo_data(i),

      error0_o => garo_err_zero(i),

      error1_o => garo_err_one(i)

    );

  end generate;

  -- GARO element connection --

  garo_intercon: process(rnd_enable, garo_en_out, garo_data, garo_err_zero, garo_err_one)

    variable data_v : std_ulogic;

    variable err0_v : std_ulogic;

    variable err1_v : std_ulogic;

  begin

    -- enable chain --

    for i in 0 to num_garos_c-1 loop

      if (i = 0) then

        garo_en_in(i) <= rnd_enable;

      else

        garo_en_in(i) <= garo_en_out(i-1);

      end if;

    end loop; -- i

    -- data & status --

    data_v := garo_data(0);

    err0_v := garo_err_zero(0);

    err1_v := garo_err_one(0);

    for i in 1 to num_garos_c-1 loop

      data_v := data_v xor garo_data(i);

      err0_v := err0_v or garo_err_zero(i);

      err1_v := err1_v or garo_err_one(i);

    end loop; -- i

    garo_res  <= data_v;

    garo_err0 <= err0_v;

    garo_err1 <= err1_v;

  end process garo_intercon;

  -- De-Biasing -----------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  jvn_debiasing_sync: process(clk_i)

  begin

    if rising_edge(clk_i) then

      db_data  <= db_data(db_data'left-1 downto 0) & garo_res;

      db_state <= (not db_state) and rnd_enable; -- just toggle when enabled -> process in every second cycle

    end if;

  end process jvn_debiasing_sync;

  -- John von Neumann De-Biasing --

  jvn_debiasing: process(db_state, db_data)

    variable tmp_v : std_ulogic_vector(2 downto 0);

  begin

    -- check groups of two non-overlapping bits from the input stream

    tmp_v := db_state & db_data(db_data'left downto db_data'left-1);

    case tmp_v is

      when "101"  => rnd_valid <= '1'; rnd_data <= '1'; -- rising edge -> '1'

      when "110"  => rnd_valid <= '1'; rnd_data <= '0'; -- falling edge -> '0'

      when others => rnd_valid <= '0'; rnd_data <= '-'; -- invalid

    end case;

  end process jvn_debiasing;

  -- Processing Core ------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  processing_core: process(clk_i)

  begin

    if rising_edge(clk_i) then

      -- sample random data and apply post-processing --

      if (rnd_enable = '0') then

        rnd_cnt  <= (others => '0');

        rnd_sreg <= (others => '0');

      elsif (rnd_valid = '1') and (garo_en_out(garo_en_out'left) = '1') then -- valid random sample and GAROs ready?

        if (rnd_cnt = "1000") then

          rnd_cnt <= (others => '0');

        else

          rnd_cnt <= std_ulogic_vector(unsigned(rnd_cnt) + 1);

        end if;

        if (lfsr_en_c = true) then -- LFSR post-processing

          rnd_sreg <= rnd_sreg(rnd_sreg'left-1 downto 0) & (xnor_all_f(rnd_sreg and lfsr_taps_c) xnor rnd_data);

        else -- NO post-processing

          rnd_sreg <= rnd_sreg(rnd_sreg'left-1 downto 0) & rnd_data;

        end if;

      end if;

      -- data output register --

      if (rnd_cnt = "1000") then

        rnd_output <= rnd_sreg;

      end if;

      -- health check error --

      if (rnd_enable = '0') then

        rnd_error_zero <= '0';

        rnd_error_one  <= '0';

      else

        rnd_error_zero <= rnd_error_zero or garo_err0;

        rnd_error_one  <= rnd_error_one  or garo_err1;

      end if;

      -- data ready flag --

      if (rnd_cnt = "1000") then -- new sample ready?

        rnd_ready <= '1';

      elsif (rnd_enable = '0') or (rden = '1') then -- clear when deactivated or on data read

        rnd_ready <= '0';

      end if;

    end if;

  end process processing_core;

end neorv32_trng_rtl;

-- ############################################################################################################################

-- ############################################################################################################################

-- #################################################################################################

-- # << NEORV32 - True Random Number Generator (TRNG) - GARO Chain-Based Entropy Source >>         #

-- # ********************************************************************************************* #

-- # An inverter chain (ring oscillator) is used as entropy source. The inverter chain is          #

-- # constructed as GARO (Galois Ring Oscillator) TRNG, which is an "asynchronous" LFSR. The       #

-- # single inverters are connected via latches that are used to enbale/disable the TRNG. Also,    #

-- # these latches are used as additional delay element. By using unique enable signals for each   #

-- # latch, the synthesis tool cannot "optimize" (=remove) any of the inverters out of the design. #

-- # Furthermore, the latches prevent the synthesis tool from detecting combinatorial loops.       #

-- #                                                                                               #

-- # Sources:                                                                                      #

-- #  - GARO: "Experimental Assessment of FIRO- and GARO-based Noise Sources for Digital TRNG      #

-- #    Designs on FPGAs" by Martin Schramm, Reiner Dojen and Michael Heigly, 2017                 #

-- #  - Latches for platform independence: "Extended Abstract: The Butterfly PUF Protecting IP     #

-- #    on every FPGA" by Sandeep S. Kumar, Jorge Guajardo, Roel Maesyz, Geert-Jan Schrijen and    #

-- #    Pim Tuyls, Philips Research Europe, 2008                                                   #

-- # ********************************************************************************************* #

-- # BSD 3-Clause License                                                                          #

-- #                                                                                               #

-- # Copyright (c) 2020, Stephan Nolting. 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.                                                            #

-- #                                                                                               #

-- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #

-- #    endorse or promote products derived from this software without specific prior written      #

-- #    permission.                                                                                #

-- #                                                                                               #

-- # 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 HOLDER 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.                                                            #

-- # ********************************************************************************************* #

-- # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

-- #################################################################################################

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

library neorv32;

use neorv32.neorv32_package.all;

entity neorv32_trng_garo_element is

  generic (

    NUM_INV : natural := 15 -- number of inverters in chain

  );

  port (

    clk_i    : in  std_ulogic;

    enable_i : in  std_ulogic;

    enable_o : out std_ulogic;

    mask_i   : in  std_ulogic_vector(NUM_INV-2 downto 0);

    data_o   : out std_ulogic;

    error0_o : out std_ulogic;

    error1_o : out std_ulogic

  );

end neorv32_trng_garo_element;

architecture neorv32_trng_garo_element_rtl of neorv32_trng_garo_element is

  -- debugging --

  constant is_sim_c : boolean := false;

  signal inv_chain   : std_ulogic_vector(NUM_INV-1 downto 0); -- oscillator chain

  signal enable_sreg : std_ulogic_vector(NUM_INV-1 downto 0); -- enable shift register

  signal sync_ff     : std_ulogic_vector(2 downto 0); -- synchronizer

  signal cnt_zero, cnt_one : std_ulogic_vector(5 downto 0); -- stuck-at-0/1 counters

begin

  -- Sanity Check ---------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  assert ((NUM_INV mod 2) /= 0) report "NEORV32 TRNG.GARO_element: NUM_INV has to be odd." severity error;

  -- Entropy Source -------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  garo_chain: process(clk_i, enable_i, enable_sreg, mask_i, inv_chain)

  begin

    if (is_sim_c = false) then

      for i in 0 to NUM_INV-1 loop -- inverters in chain

        if (enable_i = '0') then -- start with a defined state (latch reset)

          inv_chain(i) <= '0';

        -- Using individual enable signals for each inverter - derived from a shift register - to prevent the synthesis tool

        -- from removing all but one inverter (since they implement "logical identical functions").

        -- This also allows to make the TRNG platform independent.

        elsif (enable_sreg(i) = '1') then

          -- here we have the inverter chain --

          if (i = NUM_INV-1) then -- left-most inverter?

            inv_chain(i) <= not inv_chain(0); -- direct input of right most inverter (= output signal)

          else

            -- if tap switch is ON:  use final output XORed with previous inverter's output

            -- if tap switch is OFF: just use previous inverter's output

            inv_chain(i) <= not (inv_chain(i+1) xor (inv_chain(0) and mask_i(i)));

          end if;

        end if;

      end loop; -- i

    else -- simulate as simple LFSR

      if rising_edge(clk_i) then

        if (enable_i = '0') then

          inv_chain <= (others => '0');

        else

          inv_chain(NUM_INV-1 downto 0) <= inv_chain(inv_chain'left-1 downto 0) & xnor_all_f(inv_chain(NUM_INV-2 downto 0) and mask_i);

        end if;

      end if;

    end if;

  end process garo_chain;

  -- Control --------------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  ctrl_unit: process(clk_i)

  begin

    if rising_edge(clk_i) then

      enable_sreg <= enable_sreg(enable_sreg'left-1 downto 0) & enable_i; -- activate right-most inverter first

      sync_ff     <= sync_ff(sync_ff'left-1 downto 0) & inv_chain(0); -- synchronize to prevent metastability 

    end if;

  end process ctrl_unit;

  -- output for "enable chain" --

  enable_o <= enable_sreg(enable_sreg'left);

  -- rnd output --

  data_o <= sync_ff(sync_ff'left);

  -- Health Check ---------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  health_check: process(clk_i)

  begin

    if rising_edge(clk_i) then

      if (enable_sreg(enable_sreg'left) = '0') then

        cnt_zero <= (others => '0');

        cnt_one  <= (others => '0');

      else

        -- stuck-at-zero --

        if (and_all_f(cnt_zero) = '0') then -- max not reached yet

          error0_o <= '0';

          if (sync_ff(sync_ff'left) = '0') then

            cnt_zero <= std_ulogic_vector(unsigned(cnt_zero) + 1);

          else

            cnt_zero <= (others => '0');

          end if;

        else

          error0_o <= '1';

        end if;

        -- stuck-at-one --

        if (and_all_f(cnt_one) = '0') then -- max not reached yet

          error1_o <= '0';

          if (sync_ff(sync_ff'left) = '1') then

            cnt_one <= std_ulogic_vector(unsigned(cnt_one) + 1);

          else

            cnt_one <= (others => '0');

          end if;

        else

          error1_o <= '1';

        end if;

      end if;

    end if;

  end process health_check;

end neorv32_trng_garo_element_rtl;