MD5 in Delphi/Pascal/FreePascal for short strings

Question

I am trying to implement simple MD5 for short strings (shorter than 64 bytes). I am using algorithm from Wikipedia.. Everything compiles, but my result for string:

"hello world" 

is:

BB3BB65ED0EE1EE0BB22CB93C3CD5A8F

while it should be:

5EB63BBBE01EEED093CB22BB8F5ACDC3

The full code is here:

program Prog;

uses Classes, SysUtils;

function leftrotate(x, c: Cardinal): Cardinal;
begin
  leftrotate := (x shl c) or (x shr (32-c));
end;

const s: array[0..63] of Cardinal = (
    7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,
    5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,
    4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,
    6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21 );
K: array[0..63] of Cardinal = (
    $d76aa478, $e8c7b756, $242070db, $c1bdceee,
    $f57c0faf, $4787c62a, $a8304613, $fd469501,
    $698098d8, $8b44f7af, $ffff5bb1, $895cd7be,
    $6b901122, $fd987193, $a679438e, $49b40821,
    $f61e2562, $c040b340, $265e5a51, $e9b6c7aa,
    $d62f105d, $02441453, $d8a1e681, $e7d3fbc8,
    $21e1cde6, $c33707d6, $f4d50d87, $455a14ed,
    $a9e3e905, $fcefa3f8, $676f02d9, $8d2a4c8a,
    $fffa3942, $8771f681, $6d9d6122, $fde5380c,
    $a4beea44, $4bdecfa9, $f6bb4b60, $bebfbc70,
    $289b7ec6, $eaa127fa, $d4ef3085, $04881d05,
    $d9d4d039, $e6db99e5, $1fa27cf8, $c4ac5665,
    $f4292244, $432aff97, $ab9423a7, $fc93a039,
    $655b59c3, $8f0ccc92, $ffeff47d, $85845dd1,
    $6fa87e4f, $fe2ce6e0, $a3014314, $4e0811a1,
    $f7537e82, $bd3af235, $2ad7d2bb, $eb86d391 );

var a0,b0,c0,d0, a,b,c,d, f,g,dTemp: Cardinal;
   Len: Integer;
   Msg: array[0..63] of Char;
   M: array[0..15] of Cardinal absolute Msg; //break chunk into sixteen 32-bit words M[j]
   Str: String;
   i: Integer;
   ff: TFileStream;
   wait: Char;
begin
  a0 := $67452301;
  b0 := $efcdab89;
  c0 := $98badcfe;
  d0 := $10325476;

  Str := 'hello world';
  Len := Length(Str);

  FillChar(Msg, 64, 0);

  for i:=1 to Len do Msg[i-1] := Str[i];

//append "1" bit to message
  Msg[Len] := chr(128);

//append original length in bits mod (2 pow 64) to message
  Msg[63-7] := chr(8*Len);  //Update thanks to @MBo

//Process each 512-bit chunk of message- 1 only have 1 chunk

//TEST dump
//  ff := TFileStream.create('test.txt', fmCreate);
//  ff.write(msg, 64);
//  ff.free;

//Initialize hash value for this chunk:
    A := a0;
    B := b0;
    C := c0;
    D := d0;

//Main loop:
    for i := 0 to 63 do begin

        if (i>=0) and (i<=15) then begin
            F := (B and C) or ((not B) and D);
            g := i;
        end
        else if (i>=16) and (i<=31) then begin
            F := (D and B) or ((not D) and C);
            g := (5*i + 1) mod 16;
        end
        else if (i>=32) and (i<=47) then begin
            F := B xor C xor D;
            g := (3*i + 5) mod 16;
        end
        else if (i>=48) and (i<=63) then begin
            F := C xor (B or (not D));
            g := (7*i) mod 16;
        end;

        dTemp := D;
        D := C;
        C := B;
        B := B + leftrotate((A + F + K[i] + M[g]), s[i]);
        A := dTemp;
    end;

//Add this chunk's hash to result so far:
  a0 := a0 + A;
  b0 := b0 + B;
  c0 := c0 + C;
  d0 := d0 + D;

  //This should give 5EB63BBBE01EEED093CB22BB8F5ACDC3
  Writeln( IntToHex(a0,8) + IntToHex(b0,8) + IntToHex(c0,8)  +IntToHex(d0,8) );

  Readln(wait);
end.

You can try the code online here: http://ideone.com/qdYQ6q

And here's dump of my prepared chunk just before main loop (test.txt):

Answer 1

The last step is wrong:

  a0 := a0 + A;
  b0 := b0 + B;
  c0 := c0 + C;
  d0 := d0 + D;

it should change endianess:

  a0 := Swap32(a0 + A);
  b0 := Swap32(b0 + B);
  c0 := Swap32(c0 + C);
  d0 := Swap32(d0 + D);

function Swap32(ALong: Cardinal): Cardinal; Assembler; 
asm 
  BSWAP eax 
end;

and then it's good.

Answer 2

What about these steps:

append "0" bit until message length in bits ≡ 448 (mod 512)

(56 bytes, 64+56 and so on) and

append original length in bits mod (2 pow 64) to message

but you appended Len in bytes

P.S. I've checked you last variant with Delphi. I've changed char types to AnsiChar, and result is consistent with expected one. Note that byte swapping is not needed for correct binary result. It may help only for constructing hex string from Int32 values

Int32 are already little-endian on Intel hardware, so BB3BB65E (hex string representation) corresponds to byte sequence 5E B6 3B BB and so on.

Answer 3

You might want to consider using a third-party implementation instead of creating your own. For example, Indy's TIdHashMessageDigest5 class produces the correct value, eg:

uses
  ..., IdHashMessageDigest;

var
  S: string;
begin
  with TIdHashMessageDigest5.Create do
  try
    S := HashStringAsHex('hello world'); // returns '5EB63BBBE01EEED093CB22BB8F5ACDC3'
  finally
    Free;
  end;
end;