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Playfair cipher: Difference between revisions
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Output example: HI DE TH EG OL DI NT HE TR EX ES TU MP.
=={{header|C++}}==
<lang cpp>
#include <iostream>
#include <string>
//--------------------------------------------------------------------------------------------------
using namespace std;
//--------------------------------------------------------------------------------------------------
class playfair
{
public:
void doIt( string k, string t, bool ij, bool e )
{
createGrid( k, ij ); getTextReady( t, ij, e );
if( e ) doIt( 1 ); else doIt( -1 );
display();
}
private:
void doIt( int dir )
{
int a, b, c, d; string ntxt;
for( string::iterator ti = _txt.begin(); ti != _txt.end(); ti++ )
{
if( getCharPos( ( *ti++ ), a, b ) )
if( getCharPos( ( *ti ), c, d ) )
{
if( a == c ) { ntxt.append( getChar( a, b + dir ), 1 ); ntxt.append( getChar( c, d + dir ), 1 ); }
else if( b == d ){ ntxt.append( getChar( a + dir, b ), 1 ); ntxt.append( getChar( c + dir, d ), 1 ); }
else { ntxt.append( getChar( c, b ), 1 ); ntxt.append( getChar( a, d ), 1 ); }
}
}
_txt = ntxt;
}
void display()
{
cout << "\n\n OUTPUT:\n=========" << endl;
string::iterator si = _txt.begin(); int cnt = 0;
while( si != _txt.end() )
{
cout << ( *si ); si++; cout << ( *si ) << " "; si++;
if( ++cnt >= 26 ) cout << endl, cnt = 0;
}
cout << endl << endl;
}
char* getChar( int a, int b )
{
if( a > 4 ) a = 0; if( b > 4 ) b = 0;
if( a < 0 ) a = 4; if( b < 0 ) b = 4;
return &_m[a + 5 * b];
}
bool getCharPos( char l, int &a, int &b )
{
for( int y = 0; y < 5; y++ )
{
int yy = 5 * y;
for( int x = 0; x < 5; x++ )
if( _m[x + yy] == l )
{ a = x; b = y; return true; }
}
return false;
}
void getTextReady( string t, bool ij, bool e )
{
for( string::iterator si = t.begin(); si != t.end(); si++ )
{
( *si ) = toupper( ( *si ) ); if( ( *si ) < 65 || ( *si ) > 90 ) continue;
if( ( *si ) == 'J' && ij ) ( *si ) = 'I';
else if( ( *si ) == 'Q' && !ij ) continue;
_txt.append( &( *si ), 1 );
}
if( e )
{
string ntxt = ""; size_t len = _txt.length();
for( size_t x = 0; x < len; x += 2 )
{
ntxt.append( &_txt[x], 1 );
if( x + 1 < len )
{
if( _txt[x] == _txt[x + 1] ) ntxt.append( "X" );
ntxt.append( &_txt[x + 1], 1 );
}
}
_txt = ntxt;
}
if( _txt.length() & 1 ) _txt.append( "X", 1 );
}
void createGrid( string k, bool ij )
{
if( k.length() < 1 ) k = "KEYWORD";
k.append( "ABCDEFGHIJKLMNOPQRSTUVWXYZ" ); string nk = "";
for( string::iterator si = k.begin(); si != k.end(); si++ )
{
( *si ) = toupper( ( *si ) ); if( ( *si ) < 65 || ( *si ) > 90 ) continue;
if( ( ( *si ) == 'J' && ij ) || ( ( *si ) == 'Q' && !ij ) )continue;
if( nk.find( ( *si ) ) == -1 ) nk.append( &( *si ), 1 );
}
copy( nk.begin(), nk.end(), _m );
}
string _txt; char _m[25];
};
//--------------------------------------------------------------------------------------------------
int main( int argc, char* argv[] )
{
string key, i, txt; bool ij, e;
cout << "(E)ncode or (D)ecode? "; getline( cin, i ); e = ( i[0] == 'e' || i[0] == 'E' );
cout << "Enter a en/decryption key: "; getline( cin, key );
cout << "I <-> J (Y/N): "; getline( cin, i ); ij = ( i[0] == 'y' || i[0] == 'Y' );
cout << "Enter the text: "; getline( cin, txt );
playfair pf; pf.doIt( key, txt, ij, e ); return system( "pause" );
}
//--------------------------------------------------------------------------------------------------
</lang>
{{out}}<pre>
(E)ncode or (D)ecode? e
Enter a en/decryption key: playfair example
I <-> J (Y/N): y
Enter the text: Hide the gold in the tree stump
OUTPUT:
=========
BM OD ZB XD NA BE KU DM UI XM MO UV IF
(E)ncode or (D)ecode? d
Enter a en/decryption key: playfair example
I <-> J (Y/N): y
Enter the text: BMODZBXDNABEKUDMUIXMMOUVIF
OUTPUT:
=========
HI DE TH EG OL DI NT HE TR EX ES TU MP
</pre>
=={{header|Perl 6}}==
<lang perl6># Instantiate a specific encoder/decoder.
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