求算法.

[ermao998]

需要一个加密算法,要求不换密钥的前提下每次加密后密文都不一样,
对称或非对称均可,谢谢.

[wudi_1982]

Function jjm (Src:String; Key:String; Encrypt : Boolean):string;
var
idx :integer;
KeyLen :Integer;
KeyPos :Integer;
offset :Integer;
dest :string;
SrcPos :Integer;
SrcAsc :Integer;
TmpSrcAsc :Integer;
Range :Integer;

begin
KeyLen:=Length(Key);
if KeyLen = 0 then key:='Tom Lee';
KeyPos:=0;
SrcPos:=0;
SrcAsc:=0;
Range:=256;
if Encrypt then
begin
Randomize;
offset:=Random(Range);
dest:=format('%1.2x',[offset]);
for SrcPos := 1 to Length(Src) do
begin
SrcAsc:=(Ord(Src[SrcPos]) + offset) MOD 255;
if KeyPos < KeyLen then KeyPos:= KeyPos + 1 else KeyPos:=1;
SrcAsc:= SrcAsc xor Ord(Key[KeyPos]);
dest:=dest + format('%1.2x',[SrcAsc]);
offset:=SrcAsc;
end;
end
else
begin
offset:=StrToInt('$'+ copy(src,1,2));
SrcPos:=3;
repeat
SrcAsc:=StrToInt('$'+ copy(src,SrcPos,2));
if KeyPos < KeyLen Then KeyPos := KeyPos + 1 else KeyPos := 1;
TmpSrcAsc := SrcAsc xor Ord(Key[KeyPos]);
if TmpSrcAsc <= offset then
TmpSrcAsc := 255 + TmpSrcAsc - offset
else
TmpSrcAsc := TmpSrcAsc - offset;
dest := dest + chr(TmpSrcAsc);
offset:=srcAsc;
SrcPos:=SrcPos + 2;
until SrcPos >= Length(Src);
end;
Result:=Dest;
end;

procedure TForm1.BitBtn3Click(Sender: TObject);
var
s : string;
begin
s := jjm('wudi','wudi',true);
showmessage(s);
s := jjm(s,'wudi',false);
ShowMessage(s);
end;