Question

Any C++ coders on here?

Answer 1

ya

Answer 2

U know what an LFSR is??

Answer 3

linear feedback shift register

Answer 4

is a shift register whose input bit is a linear function of its previous state.

Answer 5

I wrote a program using classes and dynamic memory allocation to generate a key using an LFSR. It has no syntactical errors, though its getting hung up...logical errors galore..can u check it?

Answer 6

take it easy! first let me understand wass u r problem is ....

Answer 7

http://en.wikipedia.org/wiki/Linear_feedback_shift_register
this talks about LSFR and is written by me and Jake luther so go to it

Answer 8

now can u understand or understood him

Answer 9

i know what it is..the program isnt working

Answer 10

have you entered this or.....
#include <stdint.h>
uint16_t lfsr = 0xACE1u;
unsigned bit;
unsigned period = 0;
do {
/* taps: 16 14 13 11; characteristic polynomial: x^16 + x^14 + x^13 + x^11 + 1 */
bit = ((lfsr >> 0) ^ (lfsr >> 2) ^ (lfsr >> 3) ^ (lfsr >> 5) ) & 1;
lfsr = (lfsr >> 1) | (bit << 15);
++period;
} while(lfsr != 0xACE1u);

Answer 11

i wrote a simple code of accepting a seed and taps from a user and doing repeated xor, and then pushing the results into a key using a linked list

Answer 12

whats that

Answer 13

wass your processor imean in bit counts 64 or 32

Answer 14

32

Answer 15

correct
then its #include <stdint.h>
uint32_t lfsr = 1;
unsigned period = 0;

do {
/* taps: 32 31 29 1; characteristic polynomial: x^32 + x^31 + x^29 + x + 1 */
lfsr = (lfsr >> 1) ^ (-(lfsr & 1u) & 0xD0000001u);
++period;
} while(lfsr != 1u);

Answer 16

i mean
#include <stdint.h>
uint32_t lfsr = 1;
unsigned period = 0;

do {
/* taps: 32 31 29 1; characteristic polynomial: x^32 + x^31 + x^29 + x + 1 */
lfsr = (lfsr >> 1) ^ (-(lfsr & 1u) & 0xD0000001u);
++period;
} while(lfsr != 1u);

this was u r input

Answer 17

i wrote my own..not this

Answer 18

try to write it

Answer 19

#include <stdio.h>
#include <conio.h>
#include <iostream.h>
#include <math.h>
#include <string.h>
int xor(int ta,int tb)
{
return (ta+tb)%2;
}
struct node
{
int d;
node* l;
} ;
class key
{
node head;
public:
key()
{
head.d=0; head.l=NULL;
}
void inc(int ta)
{
node* temp;
temp=new node;
temp->d=ta;
temp->l=&head;
head=*temp;
}
void show();
} ;
void key::show()
{
node* temp;
temp=&head;
while (temp!=NULL)
{
cout<<temp->d;
temp=temp->l;
}
}
class reg
{
int* beg;
int* feedcheck;
int size;
public:
reg()
{
cout<<"Enter no of elements in register: "<<endl;
cin>>size;
beg=new int[size];
feedcheck=new int[size];
cout<<"Register formed. Press any key to seed...";
getch();
}
void seed();
void feedback();
int act();
} ;
void reg::seed()
{
clrscr();
int d;
cout<<"Enter seed of "<<size<<" digits: "<<endl;
for (int i=0;i<size;i++)
{
cin>>d; beg[i]=d;
}
cout<<"Seeded.Press any key to input feedback points...";
getch();
}
void reg::feedback()
{
int ch;
int nf;
int f;
clrscr();
for (int i=0;i<size;i++) { feedcheck[i]=0; }
cout<<"Enter no of feedback points: "<<endl;
cin>>nf;
cout<<"Enter feedback points, index starting from zero: "<<endl;
for (i=1;i<=nf;i++)
{
cin>>f;
feedcheck[f]=1;
}
cout<<"Register established...Press any key to begin key generation ";
clrscr();
}
int reg::act()
{
int res;
for (int i=0;i<size;i++)
{
if (feedcheck[i]==1)
{
res=xor(res,beg[i]);
}
}
for (i=size-2;i>=0;i--)
{
beg[i+1]=beg[i];
}
beg[0]=res;
return res;
}
void main()
{
key k;
reg r;
r.seed();
r.feedback();
int num;
cout<<"Input bit length of key: "<<endl;
cin>>num;
for (int i=1;i<=num;i++)
{
k.inc(r.act());
}
clrscr();
cout<<"Generated key: "<<endl;
k.show();
getch();
}

Answer 20

this is my code

Answer 21

thats an error coding

Answer 22

the seed function onwards is giving bugs

Answer 23

error where?

Answer 24

clrscr();
int d;
cout<<"Enter seed of "<<size<<" digits: "<<endl;
for (int i=0;i<size;i++)
{
cin>>d; beg[i]=d;
}
cout<<"Seeded.Press any key to input feedback points...";
getch();
}
void reg::feedback()
{
int ch;
int nf;
int f;
clrscr();
for (int i=0;i<size;i++) { feedcheck[i]=0; }
cout<<"Enter no of feedback points: "<<endl;
cin>>nf;
cout<<"Enter feedback points, index starting from zero: "<<endl;
for (i=1;i<=nf;i++)
{
cin>>f;
feedcheck[f]=1;
}
cout<<"Register established...Press any key to begin key generation ";
clrscr();
}
int reg::act()
{
int res;
for (int i=0;i<size;i++)
{
if (feedcheck[i]==1)
{
res=xor(res,beg[i]);
}
}
for (i=size-2;i>=0;i--)
{
beg[i+1]=beg[i];
}
beg[0]=res;
return res;
}
void main()
{
key k;
reg r;
r.seed();
r.feedback();
int num;
cout<<"Input bit length of key: "<<endl;
cin>>num;
for (int i=1;i<=num;i++)
{
k.inc(r.act());
}
clrscr();
cout<<"Generated key: "<<endl;
k.show();
getch();
}

this are error clearly visibe

Answer 25

if this is c++ than i am not going to take computer science in 11th and 12th standard ..:) just joking ... gr8 work @Master.RohanChakraborty

Answer 26

BUT WHERE?

Answer 27

thanks

Answer 28

see the codes i posted

Answer 29

So?

Answer 30

try to resolve single mistake #error in brackets

Answer 31

can you tell me which line please?

Answer 32

clrscr();
int d;

Answer 33

thanks Princess

Answer 34

you forget about brackets {

Answer 35

thats all i found

Answer 36

The brackets are there..i told you theres no syntactical error

Answer 37

FFM?

Answer 38

then some coding errors