GRE Important Link

Hello Friends,
I found some of the important links. These links will helpful for GRE. Please check out, it may help u lot. If you found it is good tell others. Else shut your mouth.

http://gredownloads.blogspot.com/

http://gredownloads.blogspot.com/2008/07/gre-barrons-audio-wordlist-by-profm.html

http://rs13.rapidshare.com/files/101496851/advanced_english_dictionary.rar

http://www.achieverspoint.com/winoverwords.htm

http://www.blogcatalog.com/blog/gre-picture-dictionary

http://www.usingenglish.com/

http://www.enchantedlearning.com/alphabet/matchwordsandpix/

http://www.manythings.org/lulu/

http://allaboutgre.blogspot.com/2006/01/sample-essays.html

http://gre-download.blogspot.com/

http://www.greguide.com

http://www.online-languages.info/_ud2/dictionary.php?l1=english&l2=marathi

http://www.statementofpurpose.com/essay_samples.html

http://www.accesseducationindia.com/gre-engineering-ms.html

http://greghost.blogspot.com/2006/09/free-gre-downloads_05.html

http://grebag.blogspot.com/

http://www.codecoax.com/grerc/

http://www.info-gre.blogspot.com/

http://gre.complore.com/

http://gre.learnhub.com/

NIS HMAC Implementation

#include
#include
#include

#define SIZE 64

typedef unsigned char uchar ;
int main ( int argc, char * argv[] )
{
FILE * kfp ;
FILE * ifp ;
FILE * ofp ;
FILE * tfp ;
uchar c[2] ;
uchar ch;
uchar key[SIZE] = { 0x00 } ;
uchar ipad[SIZE] ;
uchar opad[SIZE] ;
uchar command[100] ;
int i;

if ( 4 != argc )
{
printf( "Incorrect Usage!\n" ) ;
printf( "Correct Usage is ./hmac

" ) ;
}
for ( i = 0; i < SIZE; i++ )
{
ipad[i] = 0x36 ;
opad[i] = 0x5C ;
}


kfp = fopen( argv[1], "r+b" ) ;
ofp = fopen( argv[3], "w+b" ) ;
tfp = fopen( "temp", "w+b" ) ;

fread( key, sizeof( uchar ), SIZE, kfp ) ;
fclose ( kfp );

for ( i = 0; i < SIZE; i++ )
{
key[i] = key[i] ^ ipad[i] ;
}

fwrite( key, sizeof( uchar ), SIZE, tfp ) ;
fclose( tfp ) ;

sprintf( command, "cat %s >> temp", argv[2]) ;
system( command ) ;
system( "./md5 temp > temp1" ) ;

kfp = fopen( argv[1], "r+b" ) ;
fread( key, sizeof( uchar ), SIZE, kfp ) ;
fclose ( kfp );
for ( i = 0; i < SIZE; i++ )
{
key[i] = key[i] ^ opad[i] ;
fwrite( &key[i], sizeof( uchar ), 1, ofp ) ;
}

tfp = fopen( "temp1", "r+b" ) ;
for ( i = 0; i < 16; i++ )
{
fread( c, sizeof( uchar ), 2, tfp );
c[0] -= '0' ;
if ( c[0] > 9 )
{
c[0] = c[0] + '0' - 'a' + 10 ;
}

c[1] -= '0' ;
if ( c[1] > 9 )
{
c[1] = c[1] + '0' - 'a' + 10 ;
}
ch = ( c[0] << 4 ) | c[1] ;
fwrite( &ch, sizeof( uchar ), 1, ofp ) ;
}
fclose( ofp ) ;

sprintf( command, "./md5 %s > temp", argv[3] ) ;
system( command ) ;
system( "cat temp" ) ;
printf( "\n" ) ;

return 0;
}

//OUTPUT:

root@root:~$ ./a.out key.txt hmac.c output.txt
7d1ef72ee877ec646f700288e0693462


Kaeyfile contents:
MHCVGFDC&^$$#@%^MHCVGFDC&^$$#@%^MHCVGFDC&^$$#@%^MHCVGFDC&^$$#@%^

NIS SDES Implementation

#include
#include

typedef unsigned short int uint16 ;
typedef unsigned char uchar;

#define BIT( b, n ) ( ( b >> n ) & 0x01 )

uint16 p10( uint16 );
uint16 p8( uint16 );
uint16 p4( uint16 ) ;
uint16 ip( uint16 );
uint16 ip_inv( uint16 );
uint16 ep( uint16 );
uint16 swap( uint16 );
void print( uint16 );
void genkeys( uint16, uint16*, uint16* );
uint16 encrypt( uint16, uint16, uint16) ;



uint16 S0[4][4] =
{
{ 1, 0, 3, 2 },
{ 3, 2, 1, 0 },
{ 0, 2, 1, 3 },
{ 3, 1, 0, 3 }
};
uint16 S1[4][4] =
{
{ 0, 1, 2, 3 },
{ 2, 0, 1, 3 },
{ 3, 0, 1, 0 },
{ 2, 1, 0, 3 }
};


void dispCorrectUsage()
{
printf( "Incorrect Usage!\n" ) ;
printf( "Correct Usage is: [

]\n" ) ;
printf( "Options:\n\t-e : Encrypt input file\n\t-d: Decrypt Input file\n" ) ;
printf( "If output file is missing, the output is redirected to the standard output\n" ) ;
return;
}

int main ( int argc, char * argv[] )
{
uint16 input,output;
uint16 key,key1,key2;
uint16 tmp;
FILE * ifp;
FILE * ofp;
uchar ch;

key = 0x097;
genkeys( key, &key1, &key2 );

if ( ( argc < 2 ) || ( argc > 4 ) )
{
dispCorrectUsage();
exit( EXIT_FAILURE ) ;
}

ifp = fopen( argv[2], "r+b" ) ;
if ( NULL == ifp )
{
printf( "Unable to open Input file!\n" ) ;
exit( EXIT_FAILURE ) ;
}

if ( 4 == argc )
{
ofp = fopen( argv[3], "w+b" );
if ( NULL == ofp )
{
printf( "Unable to open Output file!\n" ) ;
exit( EXIT_FAILURE ) ;
}
}
else
{
ofp = stdout;
}

genkeys( key, &key1, &key2 );

if ( '-' == argv[1][0] )
{
if ( 'e' == argv[1][1] )
{
while ( 0 != ( fread( &ch, sizeof( uchar ), 1, ifp ) ) )
{
input = ( uint16 ) ch;
output = encrypt( input, key1, key2 ) ;
ch = ( uchar ) output;
fwrite( &ch, sizeof( uchar ), 1, ofp ) ;
}
}
else if ( 'd' == argv[1][1] )
{
while ( 0 != ( fread( &ch, sizeof( uchar ), 1, ifp ) ) )
{
input = ( uint16 ) ch;
output = encrypt( input, key2, key1 ) ;
ch = ( uchar ) output;
fwrite( &ch, sizeof( uchar ), 1, ofp ) ;
}

}
}

return 0;
}

//9876543210 -> 7583609124
uint16 p10 ( uint16 num )
{
uint16 temp = 0x00 ;

temp |= BIT( num, 7 ) << 9;
temp |= BIT( num, 5 ) << 8;
temp |= BIT( num, 8 ) << 7;
temp |= BIT( num, 3 ) << 6;
temp |= BIT( num, 6 ) << 5;
temp |= BIT( num, 0 ) << 4;
temp |= BIT( num, 9 ) << 3;
temp |= BIT( num, 1 ) << 2;
temp |= BIT( num, 2 ) << 1;
temp |= BIT( num, 4 );

return temp ;
}

//9876543210 -> 47362501
uint16 p8( uint16 num )
{
uint16 temp = 0x00 ;

temp |= BIT( num, 4 ) << 7;
temp |= BIT( num, 7 ) << 6;
temp |= BIT( num, 3 ) << 5;
temp |= BIT( num, 6 ) << 4;
temp |= BIT( num, 2 ) << 3;
temp |= BIT( num, 5 ) << 2;
temp |= BIT( num, 0 ) << 1;
temp |= BIT( num, 1 );

return temp;
}

//3210 -> 2013
uint16 p4( uint16 num )
{
uint16 temp = 0x00;

temp |= BIT( num, 2 ) << 3;
temp |= BIT( num, 0 ) << 2;
temp |= BIT( num, 1 ) << 1;
temp |= BIT( num, 3 ) ;

return temp;
}

//76543210 -> 62574031
uint16 ip( uint16 num )
{
uint16 temp = 0x00;

temp |= BIT( num, 6 ) << 7;
temp |= BIT( num, 2 ) << 6;
temp |= BIT( num, 5 ) << 5;
temp |= BIT( num, 7 ) << 4;
temp |= BIT( num, 4 ) << 3;
temp |= BIT( num, 0 ) << 2;
temp |= BIT( num, 3 ) << 1;
temp |= BIT( num, 1 );

return temp;
}


//76543210 -> 47531602
uint16 ip_inv( uint16 num )
{
uint16 temp = 0x00;

temp |= BIT( num, 4 ) << 7;
temp |= BIT( num, 7 ) << 6;
temp |= BIT( num, 5 ) << 5;
temp |= BIT( num, 3 ) << 4;
temp |= BIT( num, 1 ) << 3;
temp |= BIT( num, 6 ) << 2;
temp |= BIT( num, 0 ) << 1;
temp |= BIT( num, 2 );

return temp;
}


//3210 -> 03212103
uint16 ep( uint16 num )
{
uint16 temp = 0x00;

temp |= BIT( num, 0 ) << 7;
temp |= BIT( num, 3 ) << 6;
temp |= BIT( num, 2 ) << 5;
temp |= BIT( num, 1 ) << 4;
temp |= BIT( num, 2 ) << 3;
temp |= BIT( num, 1 ) << 2;
temp |= BIT( num, 0 ) << 1;
temp |= BIT( num, 3 );

return temp;
}

//76543210 -> 32107654
uint16 swap( uint16 num )
{
uint16 temp = 0x00;

temp |= BIT( num, 3 ) << 7;
temp |= BIT( num, 2 ) << 6;
temp |= BIT( num, 1 ) << 5;
temp |= BIT( num, 0 ) << 4;
temp |= BIT( num, 7 ) << 3;
temp |= BIT( num, 6 ) << 2;
temp |= BIT( num, 5 ) << 1;
temp |= BIT( num, 4 );

return temp;
}

// rotate x left y bits, total size is 5 bits
#define ROT_L5(x,y) ((( (x) << (y) ) | ( (x) >> (5-y) )) & 0x1F )
// get the right 5 bits of x
#define RIGHT5(x) ( (x) & 0x1F )
// get the left 5 bits of x
#define LEFT5(x) ( ( (x) >> 5 ) & 0x1F )
// get the right 4 bits of x
#define RIGHT4(x) ( (x) & 0x0F )
// get the left 4 bits of x
#define LEFT4(x) ( ( (x) >> 4 ) & 0x0F )



void print( uint16 num )
{
int i;

for ( i = 9; i >= 0; i-- )
{
printf( "%u", BIT( num, i ) ) ;
}

return;
}

// Generating the two keys
void genkeys( uint16 key, uint16* key1, uint16* key2 )
{
uint16 k1, k2;
uint16 temp;
uint16 left, right;

temp = p10( key ) ;
left = LEFT5( temp ) ;
right = RIGHT5( temp ) ;

left = ROT_L5( left, 1 );
right = ROT_L5( right, 1 );
temp = ( left << 5 ) | right ;
k1 = p8( temp ) ;

left = ROT_L5( left, 2 ) ;
right = ROT_L5( right, 2 ) ;
temp = ( left << 5 ) | right ;
k2 = p8( temp ) ;

*key1 = k1;
*key2 = k2;
return;
}

uint16 F( uint16 input, uint16 key )
{
uint16 answer= 0x00;
uint16 temp;
uint16 left;
uint16 right;
uint16 row, col;

temp = ep( input ) ;
temp = temp ^ key;
left = LEFT4( temp );
right = RIGHT4( temp );

row = ( BIT(left, 3 ) << 1 ) | BIT(left, 0 );
col = ( BIT(left, 2 ) << 1 ) | BIT(left, 1 );
answer = S0[row][col] << 2;

row = ( BIT(right, 3 ) << 1 ) | BIT(right, 0 );
col = ( BIT(right, 2 ) << 1 ) | BIT(right, 1 );
answer |= S1[row][col];

answer = p4( answer ) ;

return answer;
}


// fk(L,R,SK) = ( L ^ F(R,SK),R )
uint16 f_k( uint16 input, uint16 key )
{
uint16 answer;
uint16 left, right;
uint16 temp;

left = LEFT4( input ) ;
right = RIGHT4( input );
temp = left ^ F( right, key );
answer = ( temp << 4 ) | right ;

return answer;
}


uint16 encrypt( uint16 input, uint16 key1, uint16 key2 )
{
uint16 answer;
uint16 temp;

temp = ip( input ) ;
temp = f_k( temp, key1 ) ;
temp = swap( temp ) ;
temp = f_k( temp, key2 ) ;
answer = ip_inv( temp ) ;

return answer;
}


//OUTPUT:

C:\TC\BIN>sdes -e ip.txt op.txt

C:\TC\BIN>sdes -d op.txt
Hello World

ip.txt:-
Hello World

op.txt:-
SĺºgEég«º”

Program for sum of series

//Program to calculate the sum of series

#include
#include
long int factorial(int n);
void main()
{
int n,i;
float s,r;
char c;
clrscr();
repeat : printf("\nYou have this series:- 1/1! + 2/2! + 3/3! + 4/4! ...");
printf("\n\nTo which term you want its sum? ");
scanf("%d",&n);
s=0;
for (i=1;i<=n;i++)
{ s=s+((float)i/(float)factorial(i)); }
printf("\nThe sum of '[%d]' terms is : %f",n,s);
fflush(stdin);
printf ("\n\nDo you want to continue?(y/n):- ");
scanf("%c",&c);
if (c=='y')
goto repeat;
getch();
}

long int factorial(int n)
{
if (n<=1)
return(1);
else
n=n*factorial(n-1);
return(n);
}

Pyramid of nos

//Pyramid of Numbers

#include
#include

int pyramid( int length )
{
clrscr();
int line = 1;
int j = 1, i, k = length;

while( length-- )
{
if( j == 1 )
{
for( i = 1; i <= length + 5; i++ )
printf( "" );
printf( "%d", j++ );printf("\n");
k--;
line++;
}

else if( i % 2 )
{
for( i = 1; i <= length + 5; i++ )
printf( "" );
for( i = 1; i <= line; i++ )
printf( "%d ", ( j++ % 10 ) );
printf( "\n" );
line++;
k--;
}

else
{
for( i = 1; i <= length + 5 ; i++ )
printf( "" );
for( i = 1; i <= line; i++ )
printf( "%d ", ( j++ % 10 ) );
printf( "\n" );
line++;
k--;
}
}

return 0;
}

int main( )
{
clrscr();
int length;

printf( "Enter the list length" );
scanf( "%d", &length );

pyramid( length );
getch( );
return 0;
}

Polynomial Multiplication

//Polynomial Multiplication

#include
#include
#include

typedef struct poly
{
int coeff,expo;
}P;
P p1[10],p2[10],p3[20]={0};
int t1,t2;

void multiply();

void main()
{
int i,ch;
char cho;
clrscr();

printf("Please enter number of terms in p1: ");
scanf("%d",&t1);
printf("\nPlease enter coeff. & expo of terms in p1\n");
for(i=0;i {
scanf("%d%d",&p1[i].coeff,&p1[i].expo);
}
printf("\n\nPlease enter number of terms in p2: ");
scanf("%d",&t2);
printf("\nPlease enter coeff. & expo of terms in p2\n");
for(i=0;i {
scanf("%d%d",&p2[i].coeff,&p2[i].expo);
}

do
{
clrscr();
printf("First polynomial is\n");
for(i=0;i<(t1-1);i++)
{
printf("(%d x^%d) + ",p1[i].coeff,p1[i].expo);
}
printf("(%d x^%d)",p1[i].coeff,p1[i].expo);
printf("\n\nSecond polynomial is\n");
for(i=0;i<(t2-1);i++)
{
printf("(%d x^%d) + ",p2[i].coeff,p2[i].expo);
}
printf("(%d x^%d)",p2[i].coeff,p2[i].expo);

printf("\n\n\tYour choices are:\n");
printf(" \t1:Multiplication\n \t2:Exit\n\n");
printf("\n\nPlease enter your choice: ");
scanf("%d",&ch);

switch(ch)
{
case 1:
multiply();
break;

case 2:
exit();

default:
printf("\n\nInvalid choice");
}
printf("\nPress y to continue and any other key to stop:");
fflush(stdin);
scanf("%c",&ch);
}
while(cho=='y' || cho=='Y');
getch();
}

void multiply()
{
int i=0,j=0,k=0,cnt=0,exp,coef,flag;
for(i=0;i<20;i++)
{
p3[i].coeff=0;
p3[i].expo=0;
}
i=0;
while(i {
j=0;
while(j {
flag=0;
coef=p1[i].coeff*p2[j].coeff;
exp=p1[i].expo+p2[j].expo;
for(cnt=0;cnt {
if(p3[cnt].expo==exp)
{
p3[cnt].coeff=p3[cnt].coeff+coef;
flag=1;
}
}
if(flag==0)
{
p3[k].expo=exp;
p3[k].coeff=coef;
k++;
}
j++;
}
i++;
}
printf("\nMultiplication is \n");
for(i=0;i<(k-1);i++)
{
printf("(%d x^%d) + ",p3[i].coeff,p3[i].expo);
}
printf("(%d x^%d)",p3[i].coeff,p3[i].expo);
}

Vowels Count

//Program to calculate frequency of vowels in a string

#include
#include
void main()
{
int a=0,e=0,i=0,o=0,u=0,sum=0;
char c;
clrscr();
printf("\nEnter string:- ");
printf("\nString will be terminated if you press Ctrl-Z & then ENTER.");
printf("\nSTRING:- ");
while ((c=getchar())!=EOF)
{
if (c=='a'||c=='A')
a=a+1;
if (c=='e'||c=='E')
e=e+1;
if (c=='i'||c=='I')
i=i+1;
if (c=='o'||c=='O')
o=o+1;
if (c=='u'||c=='U')
u=u+1;
}

sum=a+e+i+o+u;
printf("\n\nFrequency of vowel 'a' is %d.",a);
printf("\nFrequency of vowel 'e' is %d.",e);
printf("\nFrequency of vowel 'i' is %d.",i);
printf("\nFrequency of vowel 'o' is %d.",o);
printf("\nFrequency of vowel 'u' is %d.",u);
printf("\nTotal no. of vowels in the text is %d.",sum);
printf("\n\nHAVE A NICE DAY! BYE.");
getch();
}