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data_encryption_standard_implementation.c
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data_encryption_standard_implementation.c
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/*
Author: Syed Afran Ali
--- DES Encryption */
/* Key Terms Used :
K56 = 56 bit Key
K48 = 48 bit Key
ORM = Old Right Message
OLM = Old Left Message
NLM = New Left Message
NRM = New Right Message
ORK = Old Right Key
OLK = Old Left Key
NLK = New Left Key
NRK = New Right Key
enCrypted = Final Encrypted Message
xor_of_48() = 48 bit key xor with 48 bit P.T.
compress() = 56 bit to 48 bit Conversion
Rest all are self explainatory */
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
/* Assigning values in matrix to be used later */
int key_permu1[] = {57, 49, 41, 33, 25, 17, 9,
1, 58, 50, 42, 34, 26, 18,
10, 2, 59, 51, 43, 35, 27,
19, 11, 3, 60, 52, 44, 36,
63, 55, 47, 39, 31, 23, 15,
7, 62, 54, 46, 38, 30, 22,
14, 6, 61, 53, 45, 37, 29,
21, 13, 5, 28, 20, 12, 4};
int key_permu2[] = {14, 17, 11, 24, 1, 5,
3, 28, 15, 6, 21, 10,
23, 19, 12, 4, 26, 8,
16, 7, 27, 20, 13, 2,
41, 52, 31, 37, 47, 55,
30, 40, 51, 45, 33, 48,
44, 49, 39, 56, 34, 53,
46, 42, 50, 36, 29, 32};
int initial_permu_message[] = {58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6,
64, 56, 48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7};
int final_permu_message[] = {40, 8, 48, 16, 56, 24, 64, 32,
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25};
int right_permu_message[] = {16, 7, 20, 21,
29, 12, 28, 17,
1, 15, 23, 26,
5, 18, 31, 10,
2, 8, 24, 14,
32, 27, 3, 9,
19, 13, 30, 6,
22, 11, 4, 25};
int message_exp[] = {32, 1, 2, 3, 4, 5,
4, 5, 6, 7, 8, 9,
8, 9, 10, 11, 12, 13,
12, 13, 14, 15, 16, 17,
16, 17, 18, 19, 20, 21,
20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29,
28, 29, 30, 31, 32, 1};
int key_shift[] = {1, 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};
int s1[4][16] = {14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13};
int s2[4][16] = {15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9};
int s3[4][16] = {10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12};
int s4[4][16] = { 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14};
int s5[4][16] = { 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3};
int s6[4][16] = {12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13};
int s7[4][16] = {4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12};
int s8[4][16] = {13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11};
/* Message to be encrypted */
char message[] ={"0101011100100101010001110110011110101010101010110100010110101110"};
/* Key used to encrypt the message */
char key[]={"0101101000110100010100110111101110011001101111001101011101110100"};
char enCrypted[64];
char ORM[32],OLM[32],ORK[28],OLK[28],temp_ORM[32];
char NRM[32],NLM[32],NRK[28],NLK[28];
char temp[64],K56[56],K48[48],RM_48[48];
int endbits,midbits;
int dec2bin(int n)
{
int dec, remain, base = 1, bin = 0, ones = 0;
dec = n;
while (n > 0)
{
remain = n % 2;
bin = bin + remain * base;
n = n / 2;
base = base * 10;
}
return bin;
}
int bin2dec(int endbits)
{
int bin, dec = 0, base = 1, remain;
bin = endbits;
while (endbits > 0)
{
remain = endbits % 10;
dec = dec + remain * base;
endbits = endbits / 10 ;
base = base * 2;
}
return dec;
}
void InDex(int a)
{
int i,flag1=0,factor=10000;
char temp[6];
for(i=a;i<a+6;i++)
{
temp[flag1] = RM_48[i];
flag1++;
}
endbits=((temp[0] -'0')*10)+(temp[5] - '0');
midbits = ((temp[1]-'0')*1000)+((temp[2]-'0')*100)+((temp[3]-'0')*10)+(temp[4]-'0');
endbits=bin2dec(endbits);
midbits = bin2dec(midbits);
}
void fiNal(int i,int bin)
{
int n,factor = 10000;
n=i+4;
while((i<n) && (factor>1))
{
factor = factor/10;
temp_ORM[i] = (bin/factor) + '0';
bin = bin % factor;
i++;
}
}
void sbox()
{
int i=0,a=0,n,bin,flag1;
InDex(0);
n = s1[endbits][midbits];
bin = dec2bin(n);
fiNal(0,bin);
a=6;
InDex(a);
n = s2[endbits][midbits];
bin = dec2bin(n);
fiNal(4,bin);
a=12;
InDex(a);
n = s3[endbits][midbits];
bin = dec2bin(n);
fiNal(8,bin);
a=18;
InDex(a);
n = s4[endbits][midbits];
bin = dec2bin(n);
fiNal(12,bin);
a=24;
InDex(a);
n = s5[endbits][midbits];
bin = dec2bin(n);
fiNal(16,bin);
a=30;
InDex(a);
n = s6[endbits][midbits];
bin = dec2bin(n);
fiNal(20,bin);
a=36;
InDex(a);
n = s7[endbits][midbits];
bin = dec2bin(n);
fiNal(24,bin);
a=42;
InDex(a);
n = s8[endbits][midbits];
bin = dec2bin(n);
fiNal(28,bin);
for(i=0;i<32;i++)
{
ORM[i]=temp_ORM[i];
}
ORM[i] = '\0';
}
/* Store the values of sbox operation in ORM */
void sbox_later()
{
int i;
char temp[32];
for(i=0;i<32;i++)
{
temp[i] = ORM[right_permu_message[i]-1];
}
for(i=0;i<32;i++)
{
ORM[i]=temp[i];
}
}
/* Perform the Shift operation */
void Lshift()
{
int i,j,flag1=0,flag2=0;
/* Right Shift */
for(j=1;j<28;j++)
{
NRK[flag2++]=ORK[j];
}
NRK[flag2++] = ORK[0];
NRK[flag2] = '\0';
/* Left Shift */
for(i=1;i<28;i++)
{
NLK[flag1++]=OLK[i];
}
NLK[flag1++] = OLK[0];
NLK[flag1] = '\0';
for(j=0;j<28;j++)
{
ORK[j]=NRK[j];
}
for(i=0;i<28;i++)
{
OLK[i]=NLK[i];
}
}
/* Convert 56 bits to 48 bits */
void compress()
{
int i,left=0,right=0,flag1=0;
for(i=0;i<56;i++)
{
if(i<28)
{
K56[i]=NLK[left];
left++;
}
else
{
K56[i]=NRK[right];
right++;
}
}
for(i=0;i<56,flag1<48;i++)
{
K48[flag1] = K56[key_permu2[i]-1];
flag1++;
}
}
/* Use left shift function to shift the key bits and than convert 56 bits to 48 */
void key_rotation(int round_n)
{
int i;
int n = key_shift[round_n];
for(i=1;i<=n;i++)
{
Lshift();
}
compress();
}
/* Perform xor operation of 48 but key and 48 bit message */
void xor_of_48()
{
int i;
for(i=0;i<48;i++)
{
if((K48[i]=='0' && RM_48[i]=='0') || (K48[i]=='1' && RM_48[i]=='1'))
RM_48[i] = '0';
else
RM_48[i] = '1';
}
}
/* Getting new right message */
void old_LR_xor()
{
int i;
for(i=0;i<32;i++)
{
if((ORM[i]=='0' && OLM[i]=='0') || (ORM[i]=='1' && OLM[i]=='1'))
NRM[i] = '0';
else
NRM[i] = '1';
}
NRM[i] = '\0';
}
/* Performing round operations and after s box printing the message */
void message_rotation()
{
int i,flag1=0;
for(i=0;i<32;i++)
{
NLM[i]=ORM[i];
}
for(i=0;i<48;i++)
{
RM_48[i] = ORM[message_exp[i]-1];
}
compress();
sbox();
sbox_later();
old_LR_xor();
for(flag1=0;flag1<32;flag1++)
{
OLM[flag1] = NLM[flag1];
ORM[flag1] = NRM[flag1];
}
OLM[flag1] = '\0';
ORM[flag1] = '\0';
printf("\n%s\n%s\n",OLM,ORM);
}
int main(void){
int i,left=0,right=0;
for(i=0;i<64;i++)
{
temp[i] = message[initial_permu_message[i]-1];
}
for(i=0;i<64;i++)
{
message[i]=temp[i];
}
for(i=0;i<64;i++)
{
if(i<32)
{
OLM[left] = message[i];
left++;
}
else
{
ORM[right] = message[i];
right++;
}
}
OLM[left] = '\0';
ORM[right] = '\0';
int flag1=0;
for(i=0;i<64,flag1<56;i++)
{
K56[flag1] = key[key_permu1[i]-1];
flag1++;
}
left=0,right=0;
for(i=0;i<56;i++)
{
if(i<28)
{
OLK[left] = K56[i];
left++;
}
else
{
ORK[right] = K56[i];
right++;
}
}
for(i=0;i<=15;i++)
{
printf("\nAfter round %d:\n",i);
key_rotation(i);
message_rotation();
}
left=0,right=0;
for(i=0;i<64;i++)
{
if(i<32)
{
message[i] = ORM[left];
left++;
}
else
{
message[i]=OLM[right];
right++;
}
}
message[i]='\0';
/* Reverse Permutation */
for(i=0;i<64;i++)
{
enCrypted[i] = message[final_permu_message[i]-1];
}
enCrypted[i]='\0';
printf("\nEncrypted Plain text\n%s\n",enCrypted);
}