Anonymous struct not inside named type

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);
}

Formatted. Link to the image is broken. Please update your question. — Stphane, Feb 27 '18 at 22:33
If you don't know what the DES algorithm is, why are you working with it? — Lightness Races in Orbit, Feb 27 '18 at 22:44

score 0 · Answer 1 · answered Feb 27 '18 at 22:45

0

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.

answered Feb 27 '18 at 22:45

Lightness Races in Orbit

378,754
76
643
1,055

Ugh my answer there actually says GCC does support it - maybe a compatibility flag is needed nowadays to get that though - someone else can pick this up :P – Lightness Races in Orbit Feb 27 '18 at 22:45

score 0 · Accepted Answer · answered Feb 27 '18 at 22:57

You are declaring anonymous structs inside of unnamed unions, just like the compiler errors say. You need to assign names to the unions (and for portability, you should name the structs, 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);
}

Anonymous struct not inside named type

2 Answers2