oracle 函数 实现简单的加密解密

create  or  replace function encrypt (in_string varchar2,shift number)  return varchar2  is 
    lv_out_string varchar2(100); 
    lv_in_string varchar2(100); 
    lv_length number(5); 
    lv_count number(5); 
    lv_temp varchar2(1); 
    lv_shift number(5); 
begin 
    lv_shift := mod(shift,26); 
    lv_in_string :=  lower(in_string); 
     select LENGTH(lv_in_string),1, ''  into lv_length,lv_count,lv_out_string  from dual; 
     
     for lv_count  in    1.. lv_length loop 
                             lv_temp := substr(lv_in_string,lv_count,1); 
                              if  ascii(lv_temp) <97     or  ascii(lv_temp) >122  then 
                                    lv_out_string := lv_out_string || lv_temp; 
                              else 
                                     if  ascii(lv_temp)+lv_shift>122  then 
                                         lv_temp :=chr( ascii(lv_temp)+lv_shift - 26); 
                                     else 
                                         lv_temp := chr( ascii(lv_temp)+lv_shift); 
                                     end  if; 
                                     lv_out_string := lv_out_string || lv_temp; 
                              end  if; 
     end loop; 
     return lv_out_string; 
end encrypt ;

create  or  replace function decrypt (in_string varchar2,shift number)  return varchar2 
is 
lv_out_string varchar2(10); 
lv_length number(3); 
lv_count number(3); 
lv_temp    varchar2(100); 
lv_shift number(3); 

begin 
                 lv_shift := mod(shift,26); 
                  select length(in_string),1, ''  into lv_length, lv_count,lv_out_string  from dual; 
                  for lv_count     in 1.. lv_length loop 
                         lv_temp :=substr(in_string,lv_count,1); 
                          if  ascii(lv_temp) <97  or  ascii(lv_temp)>122  then 
                                lv_out_string := lv_out_string || lv_temp; 
                              else 
                                     if  ascii(lv_temp)-lv_shift    <97  then 
                                         lv_temp := chr( ascii(lv_temp) - lv_shift +26); 

                                          else 
                                         lv_temp := CHR( ASCII(lv_temp) - lv_shift); 
                                     end  if; 
                                    lv_out_string := lv_out_string || lv_temp; 
                          end  if; 
                  end loop; 
                  return    lv_out_string; 
end decrypt;