Java implementations of several cryptographic algorithms include MD5, RSA, SHA256

SHA Encryption:

Package com;

Import Java.security.MessageDigest;
Import java.security.NoSuchAlgorithmException;
/**
* Getsha (String str) method available externally
* @author Randyjia
*
*/
public class SHA {
public static string Encrypt (String strsrc, String encname) {
MessageDigest MD = NULL;
StringBuilder sb = new StringBuilder ();

byte[] bt = Strsrc.getbytes ();
try {
md = Messagedigest.getinstance (encname);
Byte[] result = Md.digest (BT);
for (byte B:result) {
Sb.append (String.Format ("%02x", b));
}
} catch (NoSuchAlgorithmException e) {
return null;
}
return sb.tostring ();
}


public static void Main (String args[]) {
String s = SHA. Encrypt ("12345", "SHA-256");
System.out.println (s);

}
}

RSA Encryption:

Package com;

Import java.io.*;
Import java.security.*;

Import javax.crypto.*;
Import Java.security.spec.X509EncodedKeySpec;
Import Java.security.spec.PKCS8EncodedKeySpec;
Import sun.misc.*;

public class Rsa_test {
Private Keypairgenerator KPG = null;
Private KeyPair KP = null;
Private PublicKey public_key = null;
Private Privatekey private_key = null;

public rsa_test (int in, String address) throws NoSuchAlgorithmException,
FileNotFoundException, IOException
{
KPG = Keypairgenerator.getinstance ("RSA");
Kpg.initialize (in);
KP = Kpg.genkeypair ();
Public_key = Kp.getpublic ();
Private_key = Kp.getprivate ();

Sun.misc.BASE64Encoder b64 = new Sun.misc.BASE64Encoder ();
String pkstr = B64.encode (public_key.getencoded ());
String prstr = B64.encode (private_key.getencoded ());
System.out.print ("Pkstr Length:" +pkstr.length () + "" +pkstr);

FileWriter fw=new FileWriter (address + "/private_key.dat");
Fw.write (PRSTR);
Fw.close ();

FileWriter fw2 = new FileWriter (address + "/public_key.dat");
Fw2.write (PKSTR);
Fw2.close ();
}

Private static string encrypt (string source) throws exception{

FileReader fr = new FileReader ("e://p Ublic_key.dat ");
BufferedReader br=new BufferedReader (FR);
String Getpbkey = "";
while (true) {
String aLine = Br.readline (),
if (aline==null) break,
Getpbkey + = ALine;
}
System.out.println ("mybuilderstr:length:" + getpbkey.length () + "" +getpbkey);
Base64decoder b64d = new Base64decoder ();
Byte [] keybyte = B64d.decodebuffer (Getpbkey);
X509encodedkeyspec X509ek = new X509encodedkeyspec (keybyte);
Keyfactory keyfactory = keyfactory.getinstance ("RSA");
PublicKey PublicKey = Keyfactory.generatepublic (X509ek);

Cipher Cipher = cipher.getinstance ("RSA");
Cipher.init (Cipher.encrypt_mode,publickey);
byte[] SBT = Source.getbytes ();
Byte [] epbyte = Cipher.dofinal (SBT);
Base64encoder encoder = new Base64encoder ();
String epstr = Encoder.encode (epbyte);
return epstr;

}


public static string decrypt (string cryptograph) throws exception{

FileReader fr = new FileR Eader ("E://private_key.dat");
BufferedReader br=new BufferedReader (FR);
String Getpvkey = "";
while (true) {
String aLine = Br.readline (),
if (aline==null) break,
Getpvkey + = ALine;
}
Base64decoder b64d = new Base64decoder ();
Byte [] keybyte = B64d.decodebuffer (Getpvkey);
Pkcs8encodedkeyspec S8ek = new Pkcs8encodedkeyspec (keybyte);
Keyfactory keyfactory = keyfactory.getinstance ("RSA");
Privatekey Privatekey = keyfactory.generateprivate (S8ek);



Cipher Cipher = cipher.getinstance ("RSA");
Cipher.init (Cipher.decrypt_mode, privatekey);
Base64decoder decoder = new Base64decoder ();
Byte[] B1 = Decoder.decodebuffer (cryptograph);
Byte[] B = cipher.dofinal (B1);
return new String (b);
}

/*
public static void Main (string[] args) {
try {
New Rsa_test (1024x768, "e:/");
System.out.println ("");
String geteptstr = Encrypt ("Wuchao");
System.out.println ("Geteptstr:" +geteptstr);
String drpstr = Decrypt (GETEPTSTR);
System.out.println ("Drpstr:" +drpstr);
}
catch (IOException ex) {
Ex.printstacktrace ();
}
catch (NoSuchAlgorithmException ex) {
Ex.printstacktrace ();
}catch (Exception ex) {
Ex.printstacktrace ();
}

}
*/

}

MD5 Encryption:

Package com;

Import Java.security.MessageDigest;

public class Md5 {

Public final static String MD5 (string s) {
Char hexdigits[]={' 0 ', ' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ', ' 6 ', ' 7 ', ' 8 ', ' 9 ', ' A ', ' B ', ' C ', ' D ', ' E ', ' F '};
try {
byte[] Btinput = S.getbytes ();
MessageDigest mdinst = messagedigest.getinstance ("MD5");
Mdinst.update (Btinput);
byte[] MD = Mdinst.digest ();
int j = Md.length;
Char str[] = new CHAR[J * 2];
int k = 0;
for (int i = 0; i < J; i++) {
byte byte0 = md[i];
str[k++] = hexdigits[byte0 >>> 4 & 0xf];
str[k++] = hexdigits[byte0 & 0xf];
}
return new String (str);
} catch (Exception e) {
E.printstacktrace ();
return null;
}
}
public static void Main (string[] args) {
TODO auto-generated Method Stub
System.out.println (MD5.MD5 ("20121221ASFASFASFA"));
System.out.println (MD5.MD5 ("????"));
}

}

Java implementations of several cryptographic algorithms include MD5, RSA, SHA256