unit U_Crypt;

interface
USES
    Classes, SysUtils;
const
     C1 = 52845;             //此二常量用于生成隨機數(shù)
     C2 = 22719;

     SA:array[0..61] of char=
          ('0','1','2','3','4','5','6','7','8','9',
           'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
           'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z');

function Encrypt( S: String; Key: Word): String;   //加密函數(shù)聲明
function Decrypt( S: String; Key: Word): String;   //解密函數(shù)聲明
function Encrypt2( S: String; Key: Word): String;   //加密函數(shù)2聲明
function Decrypt2( S: String; Key: Word): String;   //解密函數(shù)2聲明

implementation

function Encrypt( S: String; Key: Word): String;
var
  I: Integer;
  j: Integer;
begin
  Result := S;
  for I := 1 to Length(S) do
  begin
    Result[I] := char(byte(S[I]) xor (Key shr 8));//將密鑰移位后與字符異或
    Key := (byte(Result[I]) + Key) * C1 + C2;  //產(chǎn)生下一個密鑰
  end;
  s:=Result;
  Result:='';
  for i:=1 to length(s) do
  begin
    j:=Integer(s[i]);                  //提取字符  ord(strtoint(s[i]));
    //j := ord(s[i]);
    Result:=Result + Char(65+(j div 26))+Char(65+(j mod 26)); //將字符轉(zhuǎn)化為兩個字母保存
  end;
end;

function Decrypt( S: String; Key: Word): String;
var
  I: Integer;
  j: Integer;
begin
  result:='';
  for i:=1 to (length(s) div 2) do    //將字符串兩個字母一組進行處理
  begin
    j:=(Integer(s[2*i-1])-65)*26;   //將兩個字母重新轉(zhuǎn)化為一個字符
    j:=j+(Integer(s[2*i])-65);
    result:=result + Char(j);       //追加字符，還原字符串
  end;
  s:=result;                      //保存中間結(jié)果
  for I := 1 to Length(S) do          //依次對字符串中各字符進行操作
  begin                              //
    Result[I] := char(byte(S[I]) xor (Key shr 8));//將密鑰移位后與字符異或
    Key := (byte(S[I]) + Key) * C1 + C2;      // 生成下一個密鑰
  end;
end;

function Encrypt2( S: String; Key: Word): String;
var
  I: Integer;
  j: Integer;
begin
  Result := S;
  for I := 1 to Length(S) do
  begin
    Result[I] := char(byte(S[I]) xor (Key shr 8));//將密鑰移位后與字符異或
    Key := (byte(Result[I]) + Key) * C1 + C2;  //產(chǎn)生下一個密鑰
  end;
  s:=Result;
  Result:='';
  for i:=1 to length(s) do
  begin
    j:=Integer(s[i]);                  //提取字符
    Result:=Result + sa[j div 62]+sa[j mod 62]; //將字符轉(zhuǎn)化為兩個字母保存
  end;
end;

function Decrypt2( S: String; Key: Word): String;
var
  I: Integer;
  j: Integer;
begin
  result:='';
  for i:=1 to (length(s) div 2) do    //將字符串兩個字母一組進行處理
  begin
    j:=(pos(s[2*i-1],sa)-1)*62;   //將兩個字符重新轉(zhuǎn)化為一個字符
    j:=j+pos(s[2*i],sa)-1;
    result:=result + char(j);       //追加字符，還原字符串
  end;
  s:=result;                      //保存中間結(jié)果
  for I := 1 to Length(S) do          //依次對字符串中各字符進行操作
  begin                              //
    Result[I] := char(byte(S[I]) xor (Key shr 8));//將密鑰移位后與字符異或
    Key := (byte(S[I]) + Key) * C1 + C2;      // 生成下一個密鑰
  end;
end;


end.