文章作者： upfeed[FCG]
/*** Source Code of MD5 ***/
/ written BY upfeed[FCG] /
/**************************/
下面的函数是计算核心，至于分组和填充部分就略去了。
====================================================
参数说明：
AA,BB,CC,DD是摘要信息，一般初始化为
AA := $67452301;
BB := $EFCDAB89;
CC := $98BADCFE;
DD := $10325476;
MSGs是一个长64的LongWord数组，保存的就是要摘要的信息
====================================================
procedure TMainForm.MD5(var AA, BB, CC, DD: LongWord; MSGs: array of LongWord);
var
A, B, C, D: LongWord;
T: array[1..64] of LongWord;
i: integer;
//没有循环左移的位运算，自己写一个
function ROL(r: LongWord; bit: byte): LongWord;
var
ii: byte;
begin
for ii:=1 to bit do
if r and $80000000 = $80000000 then
r := (r shl 1) or $01
else
r := (r shl 1);
Result := r;
end;
//四轮运算中的函数定义，也可以自行定义的
procedure FF(var a: LongWord; b, c, d: LongWord; k, s, i: byte);
begin
a := b + ROL((a + ((b and c) or (not b and d)) + MSGs[k] + T), s);
end;
procedure GG(var a: LongWord; b, c, d: LongWord; k, s, i: byte);
begin
a := b + ROL((a + ((b and d) or (c and not d)) + MSGs[k] + T), s);
end;
procedure HH(var a: LongWord; b, c, d: LongWord; k, s, i: byte);
begin
a := b + ROL((a + (b xor c xor d) + MSGs[k] + T), s);
end;
procedure II(var a: LongWord; b, c, d: LongWord; k, s, i: byte);
begin
a := b + ROL((a + (c xor (b or not d)) + MSGs[k] + T), s);
end;
begin
fillchar(T, sizeof(T), 0);
//常数数组的初始化，通常是这种形式，当然可以自己做手脚的
for i:=1 to 64 do
T := Trunc(4294967296*abs(sin(i)));
A := AA; B := BB; C := CC; D := DD;
//第一轮
FF(A, B, C, D, 0, 7, 1); FF(D, A, B, C, 1, 12, 2); FF(C, D, A, B, 2, 17, 3); FF(B, C, D, A, 3, 22, 4);
FF(A, B, C, D, 4, 7, 5); FF(D, A, B, C, 5, 12, 6); FF(C, D, A, B, 6, 17, 7); FF(B, C, D, A, 7, 22, 8);
FF(A, B, C, D, 8, 7, 9); FF(D, A, B, C, 9, 12,10); FF(C, D, A, B, 10,17,11); FF(B, C, D, A, 11,22,12);
FF(A, B, C, D, 12,7,13); FF(D, A, B, C, 13,12,14); FF(C, D, A, B, 14,17,15); FF(B, C, D, A, 15,22,16);
//第二轮
GG(A, B, C, D, 1, 5,17); GG(D, A, B, C, 6, 9,18); GG(C, D, A, B, 11,14,19); GG(B, C, D, A, 0, 20,20);
GG(A, B, C, D, 5, 5,21); GG(D, A, B, C, 10, 9,22); GG(C, D, A, B, 15,14,23); GG(B, C, D, A, 4, 20,24);
GG(A, B, C, D, 9, 5,25); GG(D, A, B, C, 14, 9,26); GG(C, D, A, B, 3, 14,27); GG(B, C, D, A, 8, 20,28);
GG(A, B, C, D, 13,5,29); GG(D, A, B, C, 2, 9,30); GG(C, D, A, B, 7, 14,31); GG(B, C, D, A, 12,20,32);
//第三轮
HH(A, B, C, D, 5, 4,33); HH(D, A, B, C, 8, 11,34); HH(C, D, A, B, 11,16,35); HH(B, C, D, A, 14,23,36);
HH(A, B, C, D, 1, 4,37); HH(D, A, B, C, 4, 11,38); HH(C, D, A, B, 7, 16,39); HH(B, C, D, A, 10,23,40);
HH(A, B, C, D, 13,4,41); HH(D, A, B, C, 0, 11,42); HH(C, D, A, B, 3, 16,43); HH(B, C, D, A, 6, 23,44);
HH(A, B, C, D, 9, 4,45); HH(D, A, B, C, 12,11,46); HH(C, D, A, B, 15,16,47); HH(B, C, D, A, 2, 23,48);
//第四轮
II(A, B, C, D, 0, 6,49); II(D, A, B, C, 7, 10,50); II(C, D, A, B, 14,15,51); II(B, C, D, A, 5, 21,52);
II(A, B, C, D, 12,6,53); II(D, A, B, C, 3, 10,54); II(C, D, A, B, 10,15,55); II(B, C, D, A, 1, 21,56);
II(A, B, C, D, 8, 6,57); II(D, A, B, C, 15,10,58); II(C, D, A, B, 6, 15,59); II(B, C, D, A, 13,21,60);
II(A, B, C, D, 4, 6,61); II(D, A, B, C, 11,10,62); II(C, D, A, B, 2, 15,63); II(B, C, D, A, 9, 21,64);
AA := A + AA;
BB := B + BB;
CC := C + CC;
DD := D + DD;
end;
