The document discusses four different encryption algorithms implemented in Java: 1. Caesar cipher which encrypts text by shifting each letter by a fixed number of positions. 2. Blowfish encryption which encrypts a password and decrypts an encrypted string. 3. Another implementation of Caesar cipher to encrypt and decrypt text with a shift of 3 positions. 4. DES encryption which encrypts and decrypts plaintext using a randomly generated DES key.

1. 1.AES for usingthe java(subjectnetworksecurity)
package aes;
importjava.io.*;
classCaesarCipher
{
publicstaticvoidmain(String[]args) throwsException
{
Stringpt,ct;
intkey=3;
BufferedReaderbr=new BufferedReader(new InputStreamReader(System.in));
System.out.print("EnterPlainText:");
pt = br.readLine().toUpperCase();
ct = doEncrypt(pt,key);
System.out.println("CipherText:" + ct);
pt = doDecrypt(ct,key);
System.out.println("DecryptedPlainText:" + pt);
}
staticString doEncrypt(Stringpt,intkey)
{
char c;
intnum;

2. StringBuffersb=newStringBuffer(pt);
for(inti=0;i<sb.length();i++)
{
num= sb.charAt(i)-65;
num+=key;
if(num>=26) num-=26;
c = (char)(num+65);
sb.setCharAt(i,c);
}
returnnewString(sb);
}
staticString doDecrypt(Stringct,intkey)
{
returndoEncrypt(ct,26-key).toLowerCase();
}
}
2. blowfishusingthe java
package blowfish;
importjavax.crypto.Cipher;
importjavax.crypto.spec.SecretKeySpec;
importsun.misc.BASE64Decoder;

3. importsun.misc.BASE64Encoder;
publicclassBlowfish{
publicstaticvoidmain(String[] args) throwsException{
encrypt("edwin","password");
decrypt("6VsVtA/nhHKUZuWWmod/BQ==");
}
private staticvoidencrypt(Stringusername,Stringpassword) throwsException{
byte[] keyData=(username+password).getBytes();
SecretKeySpecsecretKeySpec=newSecretKeySpec(keyData,"Blowfish");
Ciphercipher=Cipher.getInstance("Blowfish");
cipher.init(Cipher.ENCRYPT_MODE,secretKeySpec);
byte[] hasil =cipher.doFinal(password.getBytes());
System.out.println(new BASE64Encoder().encode(hasil));
}
private staticvoid decrypt(Stringstring) throwsException{
byte[] keyData=("edwin"+"password").getBytes();
SecretKeySpecsecretKeySpec=newSecretKeySpec(keyData,"Blowfish");
Ciphercipher=Cipher.getInstance("Blowfish");
cipher.init(Cipher.DECRYPT_MODE,secretKeySpec);
byte[] hasil =cipher.doFinal(new BASE64Decoder().decodeBuffer(string));
System.out.println(new String(hasil));

4. }
}
3. CaesarCipher
package caesarcipher;
importjava.io.*;
publicclassCaesarCipher
{
publicstaticvoidmain(String[]args) throwsException
{
Stringpt,ct;
intkey=3;
BufferedReaderbr= new BufferedReader(new InputStreamReader(System.in));
System.out.print("EnterPlainText:");
pt = br.readLine().toUpperCase();
ct = doEncrypt(pt,key);
System.out.println("CipherText:" + ct);
pt = doDecrypt(ct,key);
System.out.println("DecryptedPlainText:" + pt);
}
staticString doEncrypt(Stringpt,intkey)
{

5. char c;
intnum;
StringBuffersb= newStringBuffer(pt);
for(inti=0;i<sb.length();i++)
{
num= sb.charAt(i)-65;
num+=key;
if(num>=26) num-=26;
c = (char)(num+65);
sb.setCharAt(i,c);
}
returnnewString(sb);
}
staticvoiddoDecrypt(Stringct,intkey)
{
returndoEncrypt(ct,26-key).toLowerCase();
}
}
4. package des;
importjava.io.*;
importjavax.crypto.*;

6. importjava.security.spec.*;
importsun.misc.*;
publicclassDES
{
publicstaticvoidmain(String[]args) throwsException
{
Stringpt,ct;
SecretKeykey;
BufferedReaderbr= new BufferedReader(new InputStreamReader(System.in));
System.out.print("EnterPlainText:");
pt = br.readLine();
key= KeyGenerator.getInstance("DES").generateKey();
ct = doEncrypt(pt,key);
System.out.println("CipherText:" + ct);
pt = doDecrypt(ct,key);
System.out.println("DecryptedPlainText:" + pt);
}
staticString doEncrypt(Stringpt,SecretKeykey)throwsException
{
Cipherc = Cipher.getInstance("DES");
c.init(Cipher.ENCRYPT_MODE,key);

7. byte[] utf8= pt.getBytes("UTF8");
byte[] enc= c.doFinal(utf8);
Stringstr = newBASE64Encoder().encode(enc);
returnstr;
}
staticString doDecrypt(Stringct,SecretKeykey)throwsException
{
Cipherc = Cipher.getInstance("DES");
c.init(Cipher.DECRYPT_MODE,key);
byte[] enc= newBASE64Decoder().decodeBuffer(ct);
byte[] utf8= c.doFinal(enc);
Stringstr = newString(utf8,"UTF8");
returnstr;
}etwork
}