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eucrypt_ch6_kecca...    1  -- S.MG, 2018
eucrypt_ch6_kecca...    2 
eucrypt_ch6_kecca...    3 package body SMG_Keccak is
eucrypt_ch6_kecca...    4 
eucrypt_ch7_kecca...    5 -- public function, sponge
eucrypt_ch7_kecca...    6   procedure Sponge( Input      : in Bitstream;
eucrypt_ch7_kecca...    7                     Block_Len  : in Keccak_Rate;
eucrypt_ch7_kecca...    8                     Output     : out Bitstream) is
eucrypt_ch7_kecca...    9     Internal  : State := (others => (others => 0));
eucrypt_ch7_kecca...   10   begin
eucrypt_ch7_kecca...   11     --absorb input into sponge in a loop on available blocks, including padding
eucrypt_ch7_kecca...   12     declare
eucrypt_ch7_kecca...   13       -- number of input blocks after padding (between 2 and block_len bits pad)
eucrypt_ch7_kecca...   14       Padded_Blocks : constant Positive := 1 + (Input'Length + 1) / Block_Len;
eucrypt_ch7_kecca...   15       Padded        : Bitstream ( 1 .. Padded_Blocks * Block_Len );
eucrypt_ch7_kecca...   16       Block         : Bitstream ( 1 .. Block_Len );
eucrypt_ch7_kecca...   17     begin
eucrypt_ch7_kecca...   18       -- initialise Padded with 0 everywhere
eucrypt_ch7_kecca...   19       Padded := ( others => 0 );
eucrypt_ch7_kecca...   20       -- copy and pad input with rule 10*1
eucrypt_ch7_kecca...   21       Padded( Padded'First .. Padded'First + Input'Length - 1 ) := Input;
eucrypt_ch7_kecca...   22       Padded( Padded'First + Input'Length )                     := 1;
eucrypt_ch7_kecca...   23       Padded( Padded'Last )                                     := 1;
eucrypt_ch7_kecca...   24 
eucrypt_ch7_kecca...   25       -- loop through padded input and absorb block by block into sponge
eucrypt_ch7_kecca...   26       -- padded input IS a multiple of blocks, so no stray bits left
eucrypt_ch7_kecca...   27       for B in 0 .. Padded_Blocks - 1 loop
eucrypt_ch7_kecca...   28         -- first get the current block to absorb
eucrypt_ch7_kecca...   29         Block   := Padded( Padded'First + B * Block_Len .. 
eucrypt_ch7_kecca...   30                            Padded'First + (B+1) * Block_Len - 1 );
eucrypt_ch7_kecca...   31         AbsorbBlock( Block, Internal );
eucrypt_ch7_kecca...   32         -- scramble state with Keccak function
eucrypt_ch7_kecca...   33         Internal := Keccak_Function( Internal );
eucrypt_ch7_kecca...   34 
eucrypt_ch7_kecca...   35       end loop; -- end absorb loop for blocks
eucrypt_ch7_kecca...   36     end; -- end absorb stage
eucrypt_ch7_kecca...   37 
eucrypt_ch7_kecca...   38     --squeeze required bits from sponge in a loop as needed
eucrypt_ch7_kecca...   39     declare
eucrypt_ch7_kecca...   40       -- full blocks per output
eucrypt_ch7_kecca...   41       BPO     : constant Natural := Output'Length / Block_Len;
eucrypt_ch7_kecca...   42       -- stray bits per output
eucrypt_ch7_kecca...   43       SPO     : constant Natural := Output'Length mod Block_Len;
eucrypt_ch7_kecca...   44       Block   : Bitstream( 1 .. Block_Len );
eucrypt_ch7_kecca...   45     begin
eucrypt_ch7_kecca...   46       -- squeeze block by block (if at least one full block is needed)
eucrypt_ch7_kecca...   47       for I in 0 .. BPO - 1 loop
eucrypt_ch7_kecca...   48         SqueezeBlock( Block, Internal );
eucrypt_ch7_kecca...   49         Output( Output'First + I * Block_Len .. 
eucrypt_ch7_kecca...   50                 Output'First + (I + 1) * Block_Len -1) := Block;
eucrypt_ch7_kecca...   51  
eucrypt_ch7_kecca...   52         -- scramble state
eucrypt_ch7_kecca...   53         Internal := Keccak_Function( Internal );
eucrypt_ch7_kecca...   54       end loop;  -- end squeezing full blocks
eucrypt_ch7_kecca...   55 
eucrypt_ch7_kecca...   56       -- squeeze any partial block needed (stray bits)
eucrypt_ch7_kecca...   57       if SPO > 0 then
eucrypt_ch7_kecca...   58         SqueezeBlock( Block, Internal );
eucrypt_ch7_kecca...   59         Output( Output'Last - SPO + 1 .. Output'Last ) := 
eucrypt_ch7_kecca...   60                 Block( Block'First .. Block'First + SPO - 1 );
eucrypt_ch7_kecca...   61       end if; -- end squeezing partial last block (stray bits)
eucrypt_ch7_kecca...   62 
eucrypt_ch7_kecca...   63     end; -- end squeeze stage
eucrypt_ch7_kecca...   64   end Sponge;
eucrypt_ch7_kecca...   65 
eucrypt_ch7_kecca...   66   -- convert from a bitstream of ZWord size to an actual ZWord number
eucrypt_ch7_kecca...   67   -- first bit of bitstream will be most significant bit of ZWord
eucrypt_ch7_kecca...   68   function BitsToWord( Bits: in Bitword ) return ZWord is
eucrypt_ch7_kecca...   69     W: ZWord;
eucrypt_ch7_kecca...   70     P: Natural;
eucrypt_ch7_kecca...   71   begin
eucrypt_ch7_kecca...   72     W := 0;
eucrypt_ch7_kecca...   73     P := 0;
eucrypt_ch7_kecca...   74     for I in reverse Bitword'Range loop
eucrypt_ch7_kecca...   75       W := W + ZWord( Bits(I) ) * ( 2**P );
eucrypt_ch7_kecca...   76       P := P + 1;
eucrypt_ch7_kecca...   77     end loop;
eucrypt_ch7_kecca...   78     return W;
eucrypt_ch7_kecca...   79   end BitsToWord;
eucrypt_ch7_kecca...   80 
eucrypt_ch7_kecca...   81   -- convert from a ZWord (lane of state) to a bitstream of ZWord size
eucrypt_ch7_kecca...   82   -- most significant bit of ZWord will be left most bit of bitstream
eucrypt_ch7_kecca...   83   function WordToBits( Word: in ZWord ) return Bitword is
eucrypt_ch7_kecca...   84     Bits: Bitword := (others => 0);
eucrypt_ch7_kecca...   85     W: ZWord;
eucrypt_ch7_kecca...   86   begin
eucrypt_ch7_kecca...   87     W := Word;
eucrypt_ch7_kecca...   88     for I in reverse Bitword'Range loop
eucrypt_ch7_kecca...   89       Bits( I ) := Bit( W mod 2 );
eucrypt_ch7_kecca...   90       W := W / 2;
eucrypt_ch7_kecca...   91     end loop;
eucrypt_ch7_kecca...   92     return Bits;
eucrypt_ch7_kecca...   93   end WordToBits;
eucrypt_ch7_kecca...   94 
eucrypt_ch7_kecca...   95 -- helper procedures for sponge absorb/squeeze
eucrypt_ch7_kecca...   96 
eucrypt_ch7_kecca...   97   -- NO scramble here, this will absorb ALL given block, make sure it fits!
eucrypt_ch7_kecca...   98   procedure AbsorbBlock( Block: in Bitstream; S: in out State ) is
eucrypt_ch7_kecca...   99     WPB: constant Natural := Block'Length / Z_Length;   -- words per block
eucrypt_ch7_kecca...  100     SBB: constant Natural := Block'Length mod Z_Length; -- stray bits
eucrypt_ch7_kecca...  101     FromPos, ToPos        : Natural;
eucrypt_ch7_kecca...  102     X, Y                  : XYCoord;
eucrypt_ch7_kecca...  103     Word                  : ZWord;
eucrypt_ch7_kecca...  104     BWord                 : Bitword;
eucrypt_ch7_kecca...  105   begin
eucrypt_ch7_kecca...  106     -- xor current block into first Block'Length bits of state
eucrypt_ch7_kecca...  107     -- a block can consist in more than one word
eucrypt_ch7_kecca...  108     X := 0;
eucrypt_ch7_kecca...  109     Y := 0;
eucrypt_ch7_kecca...  110     for I in 0..WPB-1 loop
eucrypt_ch7_kecca...  111       FromPos := Block'First + I * Z_Length;
eucrypt_ch7_kecca...  112       ToPos   := FromPos + Z_Length - 1;
eucrypt_ch7_kecca...  113       Word := BitsToWord( Block( FromPos .. ToPos ) );
eucrypt_ch7_kecca...  114       S( X, Y ) := S( X, Y ) xor Word;
eucrypt_ch7_kecca...  115       -- move on to next word in state
eucrypt_ch7_kecca...  116       X := X + 1;
eucrypt_ch7_kecca...  117       if X = 0 then
eucrypt_ch7_kecca...  118         Y := Y + 1;
eucrypt_ch7_kecca...  119       end if;
eucrypt_ch7_kecca...  120     end loop;
eucrypt_ch7_kecca...  121     -- absorb also any remaining bits from block
eucrypt_ch7_kecca...  122     if SBB > 0 then
eucrypt_ch7_kecca...  123       ToPos := Block'Last;
eucrypt_ch7_kecca...  124       FromPos := ToPos - SBB + 1;
eucrypt_ch7_kecca...  125       BWord := (others => 0);
eucrypt_ch7_kecca...  126       BWord(Bitword'First .. Bitword'First + SBB - 1) := Block(ToPos..FromPos);
eucrypt_ch7_kecca...  127       Word := BitsToWord( BWord );
eucrypt_ch7_kecca...  128       S( X, Y ) := S( X, Y ) xor Word;
eucrypt_ch7_kecca...  129     end if;
eucrypt_ch7_kecca...  130   end AbsorbBlock;
eucrypt_ch7_kecca...  131 
eucrypt_ch7_kecca...  132   -- NO scramble here, this will squeeze Block'Length bits out of *same* state S
eucrypt_ch7_kecca...  133   procedure SqueezeBlock( Block: out Bitstream; S: in State) is
eucrypt_ch7_kecca...  134     X, Y    : XYCoord;
eucrypt_ch7_kecca...  135     BWord   : Bitword;
eucrypt_ch7_kecca...  136     FromPos : Natural;
eucrypt_ch7_kecca...  137     Len     : Natural;
eucrypt_ch7_kecca...  138   begin
eucrypt_ch7_kecca...  139     X := 0;
eucrypt_ch7_kecca...  140     Y := 0;
eucrypt_ch7_kecca...  141     FromPos := Block'First;
eucrypt_ch7_kecca...  142 
eucrypt_ch7_kecca...  143     while FromPos <= Block'Last loop
eucrypt_ch7_kecca...  144       BWord := WordToBits( S(X, Y) );
eucrypt_ch7_kecca...  145 
eucrypt_ch7_kecca...  146       X := X + 1;
eucrypt_ch7_kecca...  147       if X = 0 then
eucrypt_ch7_kecca...  148         Y := Y + 1;
eucrypt_ch7_kecca...  149       end if;
eucrypt_ch7_kecca...  150 
eucrypt_ch7_kecca...  151       -- copy full word if it fits or
eucrypt_ch7_kecca...  152       --   only as many bits as are still needed to fill the block
eucrypt_ch7_kecca...  153       Len := Block'Last - FromPos + 1;
eucrypt_ch7_kecca...  154       if Len > Z_Length then
eucrypt_ch7_kecca...  155         Len := Z_Length;
eucrypt_ch7_kecca...  156       end if;
eucrypt_ch7_kecca...  157 
eucrypt_ch7_kecca...  158       Block(FromPos..FromPos+Len-1) := BWord(BWord'First..BWord'First+Len-1);
eucrypt_ch7_kecca...  159       FromPos := FromPos + Len;
eucrypt_ch7_kecca...  160     end loop;
eucrypt_ch7_kecca...  161   end SqueezeBlock;
eucrypt_ch7_kecca...  162 
eucrypt_ch7_kecca...  163 
eucrypt_ch7_kecca...  164 -- private, internal transformations
eucrypt_ch6_kecca...  165   function Theta(Input : in State) return State is
eucrypt_ch6_kecca...  166     Output : State;
eucrypt_ch6_kecca...  167     C      : Plane;
eucrypt_ch6_kecca...  168     W      : ZWord;
eucrypt_ch6_kecca...  169   begin
eucrypt_ch6_kecca...  170     for X in XYCoord loop
eucrypt_ch6_kecca...  171       C(X) := Input(X, 0);
eucrypt_ch6_kecca...  172       for Y in 1..XYCoord'Last loop
eucrypt_ch6_kecca...  173         C(X) := C(X) xor Input(X, Y);
eucrypt_ch6_kecca...  174       end loop;
eucrypt_ch6_kecca...  175     end loop;
eucrypt_ch6_kecca...  176 
eucrypt_ch6_kecca...  177     for X in XYCoord loop
eucrypt_ch6_kecca...  178       W := C(X-1) xor Rotate_Left(C(X+1), 1);
eucrypt_ch6_kecca...  179       for Y in XYCoord loop
eucrypt_ch6_kecca...  180         Output(X,Y) := Input(X,Y) xor W;
eucrypt_ch6_kecca...  181       end loop;
eucrypt_ch6_kecca...  182     end loop;
eucrypt_ch6_kecca...  183 
eucrypt_ch6_kecca...  184     return Output;
eucrypt_ch6_kecca...  185   end Theta;
eucrypt_ch6_kecca...  186 
eucrypt_ch6_kecca...  187   function Rho(Input : in State) return State is
eucrypt_ch6_kecca...  188     Output      : State;
eucrypt_ch6_kecca...  189     X, Y, Old_Y : XYCoord;
eucrypt_ch6_kecca...  190   begin
eucrypt_ch6_kecca...  191     Output(0,0) := Input(0,0);
eucrypt_ch6_kecca...  192     X           := 1;
eucrypt_ch6_kecca...  193     Y           := 0;
eucrypt_ch6_kecca...  194 
eucrypt_ch6_kecca...  195     for T in 0..23 loop
eucrypt_ch6_kecca...  196       Output(X, Y) := Rotate_Left(Input(X,Y), ((T+1)*(T+2)/2) mod Z_Length);
eucrypt_ch6_kecca...  197       Old_Y := Y;
eucrypt_ch6_kecca...  198       Y := 2*X + 3*Y;
eucrypt_ch6_kecca...  199       X := Old_Y;
eucrypt_ch6_kecca...  200     end loop;
eucrypt_ch6_kecca...  201     return Output;
eucrypt_ch6_kecca...  202   end rho;
eucrypt_ch6_kecca...  203 
eucrypt_ch6_kecca...  204   function Pi(Input : in State) return State is
eucrypt_ch6_kecca...  205     Output: State;
eucrypt_ch6_kecca...  206   begin
eucrypt_ch6_kecca...  207     for X in XYCoord loop
eucrypt_ch6_kecca...  208       for Y in XYCoord loop
eucrypt_ch6_kecca...  209         Output(Y, 2*X + 3*Y) := Input(X, Y);
eucrypt_ch6_kecca...  210       end loop;
eucrypt_ch6_kecca...  211     end loop;
eucrypt_ch6_kecca...  212     return Output;
eucrypt_ch6_kecca...  213   end pi;
eucrypt_ch6_kecca...  214 
eucrypt_ch6_kecca...  215   function Chi(Input : in State) return State is
eucrypt_ch6_kecca...  216     Output: State;
eucrypt_ch6_kecca...  217   begin
eucrypt_ch6_kecca...  218     for Y in XYCoord loop
eucrypt_ch6_kecca...  219       for X in XYCoord loop
eucrypt_ch6_kecca...  220         Output(X, Y) := Input(X, Y) xor 
eucrypt_ch6_kecca...  221                         ( (not Input(X + 1, Y)) and Input(X + 2, Y) );
eucrypt_ch6_kecca...  222       end loop;
eucrypt_ch6_kecca...  223     end loop;
eucrypt_ch6_kecca...  224     return Output;
eucrypt_ch6_kecca...  225   end chi;
eucrypt_ch6_kecca...  226 
eucrypt_ch6_kecca...  227   function Iota(Round_Const : in ZWord; Input : in State) return State is
eucrypt_ch6_kecca...  228     Output: State;
eucrypt_ch6_kecca...  229   begin
eucrypt_ch6_kecca...  230     Output := Input;
eucrypt_ch6_kecca...  231     Output(0,0) := Input(0,0) xor Round_Const;
eucrypt_ch6_kecca...  232     return Output;
eucrypt_ch6_kecca...  233   end iota;
eucrypt_ch6_kecca...  234 
eucrypt_ch6_kecca...  235   function Keccak_Function(Input: in State) return State is
eucrypt_ch6_kecca...  236     Output: State;
eucrypt_ch6_kecca...  237   begin
eucrypt_ch6_kecca...  238     Output := Input;
eucrypt_ch6_kecca...  239     for I in Round_Index loop
eucrypt_ch6_kecca...  240       Output := Iota(RC(I), Chi(Pi(Rho(Theta(Output)))));
eucrypt_ch6_kecca...  241     end loop;
eucrypt_ch6_kecca...  242 
eucrypt_ch6_kecca...  243     return Output;
eucrypt_ch6_kecca...  244   end Keccak_Function;
eucrypt_ch6_kecca...  245 
eucrypt_ch6_kecca...  246 end SMG_Keccak;