4-amaliy mashg’ulot

4-amaliy mashg’ulot

Mavzu: Kriptografiyaga kirish

4	14	15	1
9	7	6	12
5	11	10	8
16	2	3	13

1. 
   Boshlang’ich matn sifatida quyidagi matnni olamiz:
   

T₀=ALIJONOVIBRATJON
Ushbu ochiq matn elementlarini jadvalga tartib bilan joylashtiramiz:

J	J	O	A
I	O	N	A
O	R	B	V
N	L	I	T

1. 
   3. Shifrlangan matn jadval elementlarini satrlar bo’yicha o’qish natijasida hosil qilinadi.
   

T₁=JJOA IONA ORBV NLIT

5-amaliy mashg’ulot

Klassik shifrlar. Sezar va Vijener algoritmi
Ishdan maqsad: Shifrlash algoritmlari bilan tanishish, sezar va Vijener algoritmlari haqida ma’lumotga ega bo’lish
SEZAR ALGORITMI
DASTUR KODI

// A C++ program to illustrate Caesar Cipher Technique

#include
using namespace std;

// This function receives text and shift and

// returns the encrypted text
string encrypt(string text, int s)
{
string result = "";

// traverse text

for (int i=0;i{
// apply transformation to each character
// Encrypt Uppercase letters
if (isupper(text[i]))
result += char(int(text[i]+s-65)%26 +65);

// Encrypt Lowercase letters

else
result += char(int(text[i]+s-97)%26 +97);
}

// Return the resulting string

return result;
}

// Driver program to test the above function

int main()
{
string text="ULUGBEK";
int s = 4;
cout << "Text : " << text;
cout << "\nShift: " << s;
cout << "\nCipher: " << encrypt(text, s);
return 0;
}




2. VijEner usulida axborotni shifrlash.
1. Alfavitni belgilab olamiz.
DASTUR KODI

#include
#include
#include
using namespace std;
int main(){
int i,j,k,n;
vectorchar> > a(26,vector<char>(26));
k=0;
n=26;
for(i=0;ik=i;
for(j=0;ja[i][j]='A'+k;
k++;
if(k==26)
k=0;
}
}
cout<<"Enter the message\n";
string s;
cin>>s;
cout<<"Enter the key\n";
string key;
cin>>key;
k=0;
int mod = key.size();
for(i=key.size();ikey+=key[k%mod];
k++;
}
string encrypt;
for(i=0;iencrypt+= a[s[i]-'A'][key[i]-'A'];
}
cout<<"Encrypted message: "<return 0;
}

6-AMALIY ISH

M=ALIJONOV_IBRATJON

A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z	_	Z
0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	25

A	L	I	J	O	N	O	V	_	I	B	R	A	T	J	O	N
0	11	8	9	14	13	14	21	26	8	1	17	0	19	9	14	13

N=26
A=3

B=5
M=(a*t+b)modn
M(0)=(3*0+5)mod26=5
M(11)=(3*11+5)mod26=10
M(8)=(3*8+5)mod26=3
M(9)=(3*9+5)mod26=6
M(14)=(3*14+5)mod26=21
M(13)=(3*13+5)mod26=18
M(14)=(3*14+5)mod26=21
M(21)=(3*21+5)mod26=16
M(26)=(3*26+5)mod26=5
M(8)=(3*8+5)mod26=3
M(1)=(3*1+5)mod26=8
M(17)=(3*17+5)mod26=4
M(0)=(3*0+5)mod26=5
M(19)=(3*19+5)mod26=10
M(9)=(3*9+5)mod26=6
M(14=(3*14+5)mod26=21
M(13)=(3*13+5)mod26=18

M(sh)=F,K,D,G,V,S,V,Q,F,D,I,E,F,K,J,V,S

M_dsh(t) = (a^-1)*(t+n-b) ( mod n )

Shifr matn	F	K	D	G	V	S	V	Q	F	D	I	E	F	K	J	V	S
t(tartib raqami)	5	10	3	6	21	18	21	16	5	3	8	4	5	10	6	21	18
9*(t +26- 4)	156	288	225	252	387	360	387	342	243	225	270	0	243	288	252	387	360
9*(t+26-4) (mod 26)	0	11	8	9	14	13	14	21	26	8	1	17	0	9	19	14	13
Ochiq matn	A	L	I	J	O	N	O	V	_	I	B	R	A	T	J	O	N