LIBRARY IEEE;USE IEEE.STD_LOGIC_1164.ALL;USE IEEE.STD_LOGIC_UNSIGNED.ALL;   -- we will use CONV_INTEGERENTITY rc5_inv_enc IS    PORT    (	clr	: IN STD_LOGIC;  -- Asynchronous reset	clk	: IN STD_LOGIC;  -- Clock signal	din	: IN STD_LOGIC_VECTOR(63 DOWNTO 0);  -- 64-bit input	dout	: OUT STD_LOGIC_VECTOR(63 DOWNTO 0) -- 64-bit output     );END rc5_inv_enc;ARCHITECTURE rtl OF rc5_inv_enc IS  --round counter  SIGNAL i_cnt: STD_LOGIC_VECTOR(3 DOWNTO 0);    SIGNAL ab_xor: STD_LOGIC_VECTOR(31 DOWNTO 0);  SIGNAL a_rot: STD_LOGIC_VECTOR(31 DOWNTO 0);  SIGNAL a: STD_LOGIC_VECTOR(31 DOWNTO 0);  --register to store value A  SIGNAL a_reg: STD_LOGIC_VECTOR(31 DOWNTO 0);   SIGNAL ba_xor: STD_LOGIC_VECTOR(31 DOWNTO 0);  SIGNAL b_rot: STD_LOGIC_VECTOR(31 DOWNTO 0);  SIGNAL b: STD_LOGIC_VECTOR(31 DOWNTO 0);  --register to store value B  SIGNAL b_reg: STD_LOGIC_VECTOR(31 DOWNTO 0); TYPE rom IS ARRAY (0 TO 25) OF STD_LOGIC_VECTOR(31 DOWNTO 0); CONSTANT skey: rom:=rom'(X"9BBBD8C8",X"1A37F7FB",X"46F8E8C5",X"460C6085",X"70F83B8A", X"284B8303",X"513E1454",X"F621ED22",X"3125065D",X"11A83A5D",X"D427686B",X"713AD82D",X"4B792F99",X"2799A4DD",X"A7901C49",X"DEDE871A",X"36C03196",X"A7EFC249",X"61A78BB8",X"3B0A1D2B",X"4DBFCA76",X"AE162167",X"30D76B0A", X"43192304", X"F6CC1431", X"65046380"); BEGIN   -- B = ((B - S[2譱 +1]) >>> A) xor A;  ab_xor <= b - skey(CONV_INTEGER(i_cnt & '1'));   WITH a(4 DOWNTO 0) SELECT      b_rot<=ab_xor(0) & ab_xor(31 DOWNTO 1) WHEN "00001",     	ab_xor(1 DOWNTO 0) & ab_xor(31 DOWNTO 2) WHEN "00010",	ab_xor(2 DOWNTO 0) & ab_xor(31 DOWNTO 3) WHEN "00011",	ab_xor(3 DOWNTO 0) & ab_xor(31 DOWNTO 4) WHEN "00100",	ab_xor(4 DOWNTO 0) & ab_xor(31 DOWNTO 5) WHEN "00101",	ab_xor(5 DOWNTO 0) & ab_xor(31 DOWNTO 6) WHEN "00110",	ab_xor(6 DOWNTO 0) & ab_xor(31 DOWNTO 7) WHEN "00111",	ab_xor(7 DOWNTO 0) & ab_xor(31 DOWNTO 8) WHEN "01000",	ab_xor(8 DOWNTO 0) & ab_xor(31 DOWNTO 9) WHEN "01001",	ab_xor(9 DOWNTO 0) & ab_xor(31 DOWNTO 10) WHEN "01010",	ab_xor(10 DOWNTO 0) & ab_xor(31 DOWNTO 11) WHEN "01011",	ab_xor(11 DOWNTO 0) & ab_xor(31 DOWNTO 12) WHEN "01100",	ab_xor(12 DOWNTO 0) & ab_xor(31 DOWNTO 13) WHEN "01101",	ab_xor(13 DOWNTO 0) & ab_xor(31 DOWNTO 14) WHEN "01110",	ab_xor(14 DOWNTO 0) & ab_xor(31 DOWNTO 15) WHEN "01111",	ab_xor(15 DOWNTO 0) & ab_xor(31 DOWNTO 16) WHEN "10000",	ab_xor(16 DOWNTO 0) & ab_xor(31 DOWNTO 17) WHEN "10001",	ab_xor(17 DOWNTO 0) & ab_xor(31 DOWNTO 18) WHEN "10010",	ab_xor(18 DOWNTO 0) & ab_xor(31 DOWNTO 19) WHEN "10011",	ab_xor(19 DOWNTO 0) & ab_xor(31 DOWNTO 20) WHEN "10100",	ab_xor(20 DOWNTO 0) & ab_xor(31 DOWNTO 21) WHEN "10101",	ab_xor(21 DOWNTO 0) & ab_xor(31 DOWNTO 22) WHEN "10110",	ab_xor(22 DOWNTO 0) & ab_xor(31 DOWNTO 23) WHEN "10111",	ab_xor(23 DOWNTO 0) & ab_xor(31 DOWNTO 24) WHEN "11000",	ab_xor(24 DOWNTO 0) & ab_xor(31 DOWNTO 25) WHEN "11001",	ab_xor(25 DOWNTO 0) & ab_xor(31 DOWNTO 26) WHEN "11010",	ab_xor(26 DOWNTO 0) & ab_xor(31 DOWNTO 27) WHEN "11011",	ab_xor(27 DOWNTO 0) & ab_xor(31 DOWNTO 28) WHEN "11100",	ab_xor(28 DOWNTO 0) & ab_xor(31 DOWNTO 29) WHEN "11101",	ab_xor(29 DOWNTO 0) & ab_xor(31 DOWNTO 30) WHEN "11110",	ab_xor(30 DOWNTO 0) & ab_xor(31) WHEN "11111",	ab_xor WHEN OTHERS;  b_reg <= b_rot XOR a; --A = ((A - S[2譱]) >>> B) xor B;  ba_xor <= a - skey(CONV_INTEGER(i_cnt & '0'));  WITH b_reg(4 DOWNTO 0) SELECT    a_rot<=ba_xor(0) & ba_xor(31 DOWNTO 1) WHEN "00001",                   ba_xor(1 DOWNTO 0) & ba_xor(31 DOWNTO 2) WHEN "00010",	ba_xor(2 DOWNTO 0) & ba_xor(31 DOWNTO 3) WHEN "00011",	ba_xor(3 DOWNTO 0) & ba_xor(31 DOWNTO 4) WHEN "00100",	ba_xor(4 DOWNTO 0) & ba_xor(31 DOWNTO 5) WHEN "00101",	ba_xor(5 DOWNTO 0) & ba_xor(31 DOWNTO 6) WHEN "00110",	ba_xor(6 DOWNTO 0) & ba_xor(31 DOWNTO 7) WHEN "00111",	ba_xor(7 DOWNTO 0) & ba_xor(31 DOWNTO 8) WHEN "01000",	ba_xor(8 DOWNTO 0) & ba_xor(31 DOWNTO 9) WHEN "01001",	ba_xor(9 DOWNTO 0) & ba_xor(31 DOWNTO 10) WHEN "01010",	ba_xor(10 DOWNTO 0) & ba_xor(31 DOWNTO 11) WHEN "01011",	ba_xor(11 DOWNTO 0) & ba_xor(31 DOWNTO 12) WHEN "01100",	ba_xor(12 DOWNTO 0) & ba_xor(31 DOWNTO 13) WHEN "01101",	ba_xor(13 DOWNTO 0) & ba_xor(31 DOWNTO 14) WHEN "01110",	ba_xor(14 DOWNTO 0) & ba_xor(31 DOWNTO 15) WHEN "01111",	ba_xor(15 DOWNTO 0) & ba_xor(31 DOWNTO 16) WHEN "10000",	ba_xor(16 DOWNTO 0) & ba_xor(31 DOWNTO 17) WHEN "10001",	ba_xor(17 DOWNTO 0) & ba_xor(31 DOWNTO 18) WHEN "10010",	ba_xor(18 DOWNTO 0) & ba_xor(31 DOWNTO 19) WHEN "10011",	ba_xor(19 DOWNTO 0) & ba_xor(31 DOWNTO 20) WHEN "10100",	ba_xor(20 DOWNTO 0) & ba_xor(31 DOWNTO 21) WHEN "10101",	ba_xor(21 DOWNTO 0) & ba_xor(31 DOWNTO 22) WHEN "10110",	ba_xor(22 DOWNTO 0) & ba_xor(31 DOWNTO 23) WHEN "10111",	ba_xor(23 DOWNTO 0) & ba_xor(31 DOWNTO 24) WHEN "11000",	ba_xor(24 DOWNTO 0) & ba_xor(31 DOWNTO 25) WHEN "11001",	ba_xor(25 DOWNTO 0) & ba_xor(31 DOWNTO 26) WHEN "11010",	ba_xor(26 DOWNTO 0) & ba_xor(31 DOWNTO 27) WHEN "11011",	ba_xor(27 DOWNTO 0) & ba_xor(31 DOWNTO 28) WHEN "11100",	ba_xor(28 DOWNTO 0) & ba_xor(31 DOWNTO 29) WHEN "11101",	ba_xor(29 DOWNTO 0) & ba_xor(31 DOWNTO 30) WHEN "11110",	ba_xor(30 DOWNTO 0) & ba_xor(31) WHEN "11111",	ba_xor WHEN OTHERS;   a_reg <= a_rot XOR b_reg;-- Register APROCESS(clr, clk)  BEGIN  IF(clr='0') THEN a <= din(63 DOWNTO 32);  ELSIF(clk'EVENT AND clk='1') THEN a<=a_reg;  END IF;END PROCESS;-- Register BPROCESS(clr, clk)  BEGIN  IF(clr='0') THEN b<=din(31 DOWNTO 0);  ELSIF(clk'EVENT AND clk='1') THEN b<=b_reg;  END IF;END PROCESS;   PROCESS (clr, clk)  BEGIN  IF(clr='0') THEN      i_cnt<="1100";   ELSIF(clk'EVENT AND clk='1') THEN       IF(i_cnt="0001") THEN         i_cnt<="1100";       ELSE         i_cnt<=i_cnt-'1';       END IF;    END IF;END PROCESS;dout<= a_reg & b_reg;END rtl;