Cryptography
Crypto System
Cryptographic system are characterized along 3
independent dimensions
- The type of operation transforming plain text to cipher text
- The number of keys used
- The way in which plain text is processed.
Substitution techniques
- Caesar Cipher
- Monoalphabatic Cipher
- Playfair Cipher
- Hill Cipher
- Polyalphabatic Cipher
Transposition techniques
- Rail fence Cipher
- Columnar transposition
Sample java code for crypto System
Secret
key: Representing reverse order of alphabet
Encryption
Example: hello(plain
text)-----------svool(cipher text)
import java.util.*;
public class Encrypt{
public
static void main(String args[]){
Scanner
myScanner=new Scanner(System.in);
String
alpha="abcdefghijklmnopqrstuvwxyz";
String
word;
System.out.println("Enter
the plain text");
word=myScanner.nextLine().toLowerCase();
System.out.println("Cipher
text");
for(int
i=0;i<word.length();i++){
boolean
found=false;
char
a=word.charAt(i);
int
j=0;
while(j<alpha.length()
&& found==false){
char
b=alpha.charAt(j);
if(a=='
'){
System.out.print("
");
found=true;
}
else
if(a==b ){
found=true;
System.out.print(alpha.substring(alpha.length()-j-1,alpha.length()-j));
}
j++;
}
}
}
}
Decryption
Example: svool(cipher text)-----------hello(plain text)
import java.util.*;
public class Decrypt{
public
static void main(String args[]){
Scanner
myScanner=new Scanner(System.in);
String
alpha=" zyxwvutsrqponmlkjihgfedcba
";
String
word;
System.out.println("Enter
the cipher text");
word=myScanner.nextLine().toLowerCase();
System.out.println("original
text");
for(int
i=0;i<word.length();i++){
boolean
found=false;
char
a=word.charAt(i);
int
j=0;
while(j<alpha.length()
&& found==false){
char
b=alpha.charAt(j);
if(a=='
'){
System.out.print("
");
found=true;
}
else
if(a==b ){
found=true;
System.out.print(alpha.substring(alpha.length()-j-1,alpha.length()-j));
}
j++;
}
}
}
}
0 comments:
Post a Comment