u_encrypt.pas

以前写的一个利用P2P 技术的一个通讯的例子。里面用到了 DBISAM 、INDY 控件。

unit U_ENCRYPT;

interface
function encrypt_str_wy(Src: string; Key: string; Encrypt: Boolean; m_brand: boolean = true): string;

implementation
uses sysutils;

function encrypt_str_wy(Src: string; Key: string; Encrypt: Boolean; m_brand: boolean = true): 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 := 'lsy wangy  johnson';
   KeyPos := 0;
   SrcPos := 0;
   SrcAsc := 0;
   Range := 256;
   if Encrypt then
      begin
         Randomize;
         offset := 18;
         if m_brand then
            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;

end.