delphi 加密字符串

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function EncrypStr(Src, Key: String): String;//字符串加密函数
//对字符串加密(Src:源 Key:密匙)
var KeyLen :Integer;
    KeyPos :Integer;
    offset :Integer;
    dest :string;
    SrcPos :Integer;
    SrcAsc :Integer;
    Range :Integer;
begin
   KeyLen:=Length(Key);
   if KeyLen = 0 then key:='delphi';
   KeyPos:=0;
   Range:=256;
   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;
   Result:=Dest;
end;
end;

function UncrypStr(Src, Key: String): string;//字符串解密函数
//对字符串解密(Src:源 Key:密匙)
var KeyLen :Integer;
    KeyPos :Integer;
    offset :Integer;
    dest :string;
    SrcPos :Integer;
    SrcAsc :Integer;
    TmpSrcAsc :Integer;
begin
   KeyLen:=Length(Key);
   if KeyLen = 0 then key:='delphi';
   KeyPos:=0;
   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);
   Result:=Dest;
end;

//***************************************************************************************

//********************************************************
//             加密解密 (利用异或运算)    （方式2）
//********************************************************

function encryptstr(const s:string; skey:string):string;//加密
var
    i,j: integer;
    hexS,hexskey,midS,tmpstr:string;
    a,b,c:byte;
begin
    hexS   :=myStrtoHex(s);
    hexskey:=myStrtoHex(skey);
    midS   :=hexS;
    for i:=1 to (length(hexskey) div 2)   do
    begin
        if i<>1 then midS:= tmpstr;
        tmpstr:='';
        for j:=1 to (length(midS) div 2) do
        begin
            a:=strtoint('$'+midS[2*j-1]+midS[2*j]);
            b:=strtoint('$'+hexskey[2*i-1]+hexskey[2*i]);
            c:=a xor b;
            tmpstr := tmpstr+myStrtoHex(chr(c));
        end;
    end;
    result := tmpstr;
end;

function decryptstr(const s:string; skey:string):string;//解密
var
    i,j: integer;
    hexS,hexskey,midS,tmpstr:string;
    a,b,c:byte;
begin
    hexS :=s;//应该是该字符串
    if length(hexS) mod 2=1 then
    begin
        showmessage('密文错误！');
        exit;
    end;
    hexskey:=myStrtoHex(skey);
    tmpstr :=hexS;
    midS   :=hexS;
    for i:=(length(hexskey) div 2) downto 1 do
    begin
        if i<>(length(hexskey) div 2) then midS:= tmpstr;
        tmpstr:='';
        for j:=1 to (length(midS) div 2) do
        begin
            a:=strtoint('$'+midS[2*j-1]+midS[2*j]);
            b:=strtoint('$'+hexskey[2*i-1]+hexskey[2*i]);
            c:=a xor b;
            tmpstr := tmpstr+myStrtoHex(chr(c));
        end;
    end;
    result := myHextoStr(tmpstr);
end;