-- (C) Copyright 1999 by John Halleck,All rights reserved. -- Basic Transformation functions of NSA's Secure Hash Algorithm -- This is part of a project at http://www.cc.utah.edu/~nahaj/ package body SHA_0.Process_Data is -- Totally local functions. -- Raw transformation of the data. procedure Transform (Given : access Context); -- Align data and place in buffer. procedure Graft_On (Given : access Context; Raw : Unsigned_32; Size : Bit_Index; Increment_Count : Boolean := True); -- On with the show ----------------------------------------- -- Quick and easy routine for the most common simple case. function Digest_A_String (Given : String) return Digest is Temp : aliased Context; begin Initialize (Temp'Access); for I in Given'First .. Given'Last loop Add (Byte (Character'Pos (Given (I))), Temp'Access); end loop; return Finalize (Temp'Access); end Digest_A_String; -- Start out the buffer with a good starting state. -- Note that there are assumptions ALL over the code that the -- buffer starts out with zeros. procedure Initialize (Given : access Context := Default_Buffer) is begin Given.all := ((others => 0), 0, 32, 0, Initial_Context, True); -- If your machine doesn't have Unsigned_64, and therefore implemented -- Count as two Unsigned_32's, then the alternate code here is: -- Given.all := -- ((others => 0), (0, 0), 32, 0, Initial_Context, True); end Initialize; -- Procedures to add to the data being hashed. procedure Add (Data : Bit; Given : access Context := Default_Buffer) is begin if not Given.Initialized then raise SHA_Not_Initialized; end if; Graft_On (Given, Unsigned_32 (Data), 1); end Add; procedure Add (Data : Byte; Given : access Context := Default_Buffer) is begin if not Given.Initialized then raise SHA_Not_Initialized; end if; Graft_On (Given, Unsigned_32 (Data), 8); end Add; procedure Add (Data : Word; Given : access Context := Default_Buffer) is begin if not Given.Initialized then raise SHA_Not_Initialized; end if; Graft_On (Given, Unsigned_32 (Data), 16); end Add; procedure Add (Data : Long; Given : access Context := Default_Buffer) is begin if not Given.Initialized then raise SHA_Not_Initialized; end if; Graft_On (Given, Unsigned_32 (Data), 32); end Add; procedure Add (Data : Long; Size : Bit_Index; Given : access Context := Default_Buffer) is begin if not Given.Initialized then raise SHA_Not_Initialized; end if; Graft_On (Given, Unsigned_32 (Data), Size); end Add; -- Get the final digest. function Finalize (Given : access Context := Default_Buffer) return Digest is begin if not Given.Initialized then raise SHA_Not_Initialized; end if; -- The standard requires the Data be padded with a single 1 bit. Graft_On (Given, 1, 1, False); -- We may have to make room for the count to be put on the last block. if Given.Next_Word >= Given.Data'Last - 1 then -- Room for the count? if not (Given.Next_Word = Given.Data'Last - 1 and Given.Remaining_Bits = 32) then Transform (Given); end if; end if; -- Ok, now we can just add the count on. Given.Data (Given.Data'Last - 1) := Unsigned_32 (Shift_Right (Given.Count, 32)); Given.Data (Given.Data'Last) := Unsigned_32 (Given.Count mod 2 ** 32); -- If you don't have Unsigned_64, and you've followed the notes and -- and used two Unsigned_32's, then the code you want here is: -- Given.Data (14) := Given.Count (0); -- Given.Data (15) := Given.Count (1); -- And now we just transform that. Transform (Given); -- Ok, we are done. Given.Initialized := False; -- One aught not to reused this without -- appropriate re-initialization. return Given.Current; end Finalize; --------------------------------------------------------------------------- -- Actually put the bits we have into the buffer properly aligned. procedure Graft_On (Given : access Context; Raw : Unsigned_32; Size : Bit_Index; Increment_Count : Boolean := True) is Offset : Integer range -31 .. 32; -- How far to move to align this? Overflow : Bit_Index := 0; -- How much is into the next word? Remainder : Unsigned_32 := 0; -- What data has to be done in cleanup? Value : Unsigned_32 := Raw; -- What value are we Really working with? begin -- Huh? if Size = 0 then return; end if; -- How do we have to align the data to fit? Offset := Integer (Given.Remaining_Bits) -- Amount used - Integer (Size); -- Minus amount we have. if Offset > 0 then Value := Shift_Left (Value, Offset); elsif Offset < 0 then Remainder := Shift_Left (Value, 32 + Offset); -- -- Really "- -Offset" Value := Shift_Right (Value, -Offset); Overflow := Bit_Index (-Offset); end if; -- Insert the actual value into the table. Given.Data (Given.Next_Word) := Given.Data (Given.Next_Word) or Value; -- Update where we are in the table. if Offset > 0 then -- Not on a word boundry Given.Remaining_Bits := Given.Remaining_Bits - Size; elsif Given.Next_Word < Data_Buffer'Last then Given.Next_Word := Given.Next_Word + 1; Given.Remaining_Bits := 32; else Transform (Given); -- Also clears everything out of the buffer. end if; -- Handle anything that overflows into the next word. if Overflow /= 0 then Given.Data (Given.Next_Word) := Given.Data (Given.Next_Word) or Remainder; Given.Remaining_Bits := 32 - Overflow; end if; if Increment_Count then Given.Count := Given.Count + Unsigned_64 (Size); -- *IF* your machine doesn't support Unsigned_64, then you have to -- implement Count as two Unsigned_32's. In that case this addition -- is going to look like: -- Remainder := Given.Count (2) mod 2 ** 16; -- Remainder := Remainder + Unsigned_32 (Size); -- Value := Remainder mod 2 ** 16; -- Remainder := Shift_Right (Remainder, 16) -- + Shift_Right (Given.Count (2), 16); -- Given.Count (2) := Shift_Left (Remainder, 16) + Value; -- Given.Count (1) := Given.Count(1) -- + Shift_Right (Remainder, 16); end if; end Graft_On; --------------------------------------------------------------------------- -- The actual SHA transformation of a block of data. -- Yes, it is cryptic... But it is a pretty much direct transliteration -- of the standard, variable names and all. procedure Transform (Given : access Context) is Temp : Unsigned_32; -- Buffer to work in. type Work_Buffer is array (0 .. 79) of Unsigned_32; W : Work_Buffer; -- How much is filled from the data, how much is filled by expansion. Fill_Start : constant := Work_Buffer'First + Data_Buffer'Length; Data_End : constant := Fill_Start - 1; A : Unsigned_32 := Given.Current (0); B : Unsigned_32 := Given.Current (1); C : Unsigned_32 := Given.Current (2); D : Unsigned_32 := Given.Current (3); E : Unsigned_32 := Given.Current (4); begin for I in Work_Buffer'First .. Data_End loop W (I) := Given.Data (Word_Range (I)); end loop; for I in Fill_Start .. Work_Buffer'Last loop W (I) := W (I - 3) xor W (I - 8) xor W (I - 14) xor W (I - 16); end loop; for I in Work_Buffer'Range loop Temp := W (I) + Rotate_Left (A, 5) + E; case I is when 0 .. 19 => Temp := Temp + 16#5A827999# + ((B and C) or ((not B) and D)); when 20 .. 39 => Temp := Temp + 16#6ED9EBA1# + (B xor C xor D); when 40 .. 59 => Temp := Temp + 16#8F1BBCDC# + ((B and C) or (B and D) or (C and D)); when 60 .. 79 => Temp := Temp + 16#CA62C1D6# + (B xor C xor D); end case; E := D; D := C; C := Rotate_Right (B, 2); -- The standard really says rotate left 30. B := A; A := Temp; end loop; Given.Current := (Given.Current (0) + A, Given.Current (1) + B, Given.Current (2) + C, Given.Current (3) + D, Given.Current (4) + E ); Given.Remaining_Bits := 32; Given.Next_Word := 0; Given.Data := (others => 0); -- *THIS MUST BE DONE* end Transform; end SHA_0.Process_Data;