匿名结构不在命名类型内

Question

I have trouble with DES algorithm. How to solve this?

(I'm using DevC++ v5.11)

I don't completely understand what DES are. What should I do/try ?

// Triple DES (3DES) 
void DES::inital_key(const char key[64],char ekey[16][48],bool is_crypt)
{      
    union{                               //Error here
    char pkey[56];
    struct{char l[28],r[28];};
  };
  permute(key,pkey,_DES::perm1,56); 
  for(uint n=0; n<16; n++) {
    lshift(l,_DES::sc[n]);
    lshift(r,_DES::sc[n]);
    permute(pkey,ekey[is_crypt?n:15-n],_DES::perm2,48); 
  }
}

/////////////////////////////////////////////////////////////////////////////
void DES::work(const char in[64],char out[64],const char key[64],bool is_crypt)
{
  char ekey[16][48];                
  union{                                 //And here
    char pin[64];
    struct{char l[32],r[32];};
  };
  inital_key(key,ekey,is_crypt);
  permute(in,pin,_DES::perm3,64);
  for(uint n=0; n<16;) round(l,r,ekey[n++]),round(r,l,ekey[n++]);
  permute(pin,out,_DES::perm6,64);
}

Answer 1

This code is relying on a Microsoft extension .

Your compiler, GCC, does not understand it.

You cannot use this code unless you make it standard C++, or switch compilers.

Answer 2

You are declaring anonymous struct s inside of unnamed union s, just like the compiler errors say. You need to assign names to the union s (and for portability, you should name the struct s, too):

void DES::inital_key(const char key[64], char ekey[16][48], bool is_crypt)
{      
  union {
    char pkey[56];
    struct { char l[28], r[28]; } s;
  } u;
  permute(key, u.pkey, _DES::perm1, 56); 
  for(uint n = 0; n < 16; n++) {
    lshift(u.s.l, _DES::sc[n]);
    lshift(u.s.r, _DES::sc[n]);
    permute(u.pkey, ekey[is_crypt ? n : 15-n], _DES::perm2, 48); 
  }
}

void DES::work(const char in[64], char out[64], const char key[64], bool is_crypt)
{
  char ekey[16][48];                
  union {
    char pin[64];
    struct { char l[32], r[32]; } s;
  } u;
  inital_key(key, ekey, is_crypt);
  permute(in, u.pin, _DES::perm3, 64);
  for(uint n = 0; n < 16;) round(u.s.l,  u.s.r, ekey[n++]), round(u.s.r, u.s.l, ekey[n++]);
  permute(u.pin, out, _DES::perm6, 64);
}