Vortrag_22-9.2005

Cryptography &
Java Internet Security
1
Goals of Network Security
2
Basic Cryptographic Concepts
3
Java Security Concepts & Applets
4
Java Cryptographic Architecture (JCE) &
Java Cryptographic Extension (JCE)
5
An example: what students have to do ...
1 Goals of Network Security
Security is multilateral !
•
Confidentiality
– symmetric encoding systems (bilateral)
– asymmetric encoding systems (multilateral)
– special protocols: S-HTTP, SSL, ...
•
Integrity
– message digests, digital signatures (multilateral)
– Message Autentification Code (MAC)
•
Availability
– diversified networks
•
Commitment / attribute somebody something (requisition of services)
– digital signatures (multilateral)
Literature
•
Simon Singh
The Code Book . The Science of Secrecy from Ancient Egypt to Quantum
Cryptography
Fourth Estate, London, 1999
in german:
Geheime Botschaften. Die Kunst der Verschlüsselung von der Antike bis zum
Internet.
dtv, München 2001
Basics
Cryptology = Cryptography + Crypto analysis
Secret communication
Cryptography
Transposition
Substitution
Steganography
2 Basic Cryptographic Concepts
•
crypto system
•
cryptographically secure message digest (SHA-1, MD5, ...)
•
cryptographic cipher: encryption & decryption
– symmetric encryption (DES, IDEA, ...)
– asymmetric encryption (public key) (RSA, ElGamal, ...)
•
certificate (X.509 standard)
•
digital signatures: signing and verifying (DSA, RSA, ...)
Crypto system
M : plaintext space
C : ciphertext space
K : key space
M : plaintext message
C : ciphertext message
K : key
E = Encrypt
D = Decrypt
E(M )=C
E:M× KC
D(C )=M
D:C× KM
DK (EK (M) ) = M
|
M  M
Message Digest = one way hash function
w = h (x)
Example: w = bx (mod m)
Message Authentification Code (MAC) = hash function with secure key
w = h (x, k)
Random number
symmetric encryption
k = secure key
Key
generator
k
ciphertext
plaintext
x
encrypt
C(x)
plaintext
decrypt
x
B
A
asymmetric encryption
s = private key
Key
generator
t = public key
ciphertext
plaintext
x
decrypt
A
C(x)
plaintext
encrypt
B
x
Diffie-Hellman key exchange
Public: g= 4, p=11
A
Private key
x A= 3
B
Private key
xB= 4
Public key
yA= g xA mod p
= 4 3 mod 11
= 64 mod 11 = 9
Public key
yB= g xB mod p
= 44 mod 11
= 256 mod 11 = 3
Session key
K = yB xA mod p = 33 mod 11 = 5
K = yA xB mod p = 94 mod 11 = 5
X.509 Certificate
version
serial number
Algorithm identifier
Issuer (name of CA)
Period of validity
Subject (user name)
Public key
Signature (CA)
Random number
symmetric authentification
k = secure key
Key
generator
k
Text with authentific.
text
x
Generate
MAC
x, MAC
Text, testresult
test
MAC
x, {true | false}
B
A
asymmetric authentication
(signature system)
s = private key (sign)
Key
generator
t = public key (verify)
text
x
Text with signature
sign
A
x, sig(x)
verify
B
Text with signatur
+ testresult
x,sig(x),
{true | false}
3 Java: Security Concept & Applets
How an applet works
and how it looks like
A security manager in the JVM controls access
•
Java 1.0 Security Model
– “Sandbox Model“ :
no permission to access local resources (client)
•
Java 1.1 Security Model
– signed applets introduced : full access to local resources
– unsigned applets run in the sandbox
•
Java 1.2 Security Model
Trouble: there are differences between
appletviewer , Netscape, Microsoft IE in Java 1.1 and Java 1.2
Java 1.0 Security Model
Java 1.1 Security Model
Java 1.2 Security Model
4 Java Cryptographic Architecture (JCA) &
Java Cryptographic Extension (JCE)
•
•
Design principle: Provider - Algorithm - Concept
Classes:
SUN
MD5
SHA1
MessageDigest
X
RSA
DSA
Signature
Identity
Signer
MessageDigest
Signature
Key
KeyPair
KeyPairGenerator
KeyGenerator
SecureRamdom
KeyStore
Certificate
X509Certificate
Cipher
5 An example: what students have to do ...
•
•
Task description for students
steps:
1 give an applet rights to write a file belegis.dat on client
2 generate a keypair and a self signed certificate (X.509) ; store the keypair in a
keystore file and export certificate to a file
3 write a Java-application that produces a MD5-Message Digest of file
belegis.dat
4 write another Java-application that reads and signs the Java source code of step 3,
concatenate the source with the signature and encrypt the result (symmetric
cryptography). Deserialize a given session key for this purpose.
•
Store in a directory for verification (or send by Email):
– file belegis.dat
(load html-page)
– the self signed certificate
– the message digest
– the chiffretext
(use keytool)
(run program of step 3)
(run program of step 4)
Preparation
•
Make available - applet BelegIS.java
- HTML page BelegIS.html containing this applet
•
generate & make available (serialize) secure session key
•
generate keystore file c:\workstation\IS\mykeystore
to include certificates come from students
Solution
•
•
•
If no permissions are given to applet
give file permissions by policytool
applet writes belegis.dat now
•
generate a keystore file & a key pair
by keytool, export certificate (step 2)
•
java source code (step 3)
•
java source code (step 4)
Response to Solution
Solution‘s Verification
•
register verification time
•
import certificate
•
•
•
•
read keystore file
verify message digest
deserialize session key
decrypt chiffretext and store
temporary
extract certificate
proof validity of certificate
prepare for verifying signature
read signature
verify signature
•
•
•
•
•
import java.security.*;
import java.security.cert.*;
import java.io.*;
public class Beleg01Loes3{
public static void main(String args []){
try {
FileInputStream fi = new FileInputStream("mykeystore");
KeyStore ks = KeyStore.getInstance("JKS","SUN");
char [] passwd1 = {'r','p','l','a','c','d','1'};
ks.load(fi,passwd1);
char [] passwd2 = {'r','p','l','a','c','a','1'};
Key priv = ks.getKey("is_beleg",passwd2);
MessageDigest md = MessageDigest.getInstance("MD5");
FileInputStream fi2 =
new FileInputStream("c:/temp/belegis.dat");
byte xx =(byte)fi2.read();
while(xx != -1){
md.update(xx);
xx =(byte)fi2.read();
}
fi2.close();
System.out.println("------- Datei gelesen -------");
byte [] medi = md.digest();
FileOutputStream mdf = new FileOutputStream("belegis_MD5.dat");
mdf.write(medi);
mdf.close();
System.out.println("---- MD5 geschrieben ----");
System.out.println("---------- ende ----------");
}
catch(Exception e){
System.out.println("error:"+e);
}
}
}
import
import
import
import
import
import
import
import
java.io.*;
java.security.*;
java.security.spec.*;
java.security.interfaces.*;
java.security.cert.*;
javax.crypto.*;
javax.crypto.spec.*;
javax.crypto.interfaces.*;
public class Beleg01Loes4{
public static void main(String args[]){
try{
Provider sunJCE = new com.sun.crypto.provider.SunJCE();
Security.addProvider(sunJCE);
System.out.println("Provider eingetragen");
File f1;
File f2;
if(args.length < 2) {
System.out.println("Usage: java Beleg01Loes4 "+
" <plaintext file> <chiffretext file> ");
System.exit(8);
}
f1 = new File(args[0]);
f2 = new File(args[1]);
FileInputStream fis;
FileOutputStream fos;
FileInputStream kfis;
FileOutputStream kfos;
fis = new FileInputStream(f1);
fos = new FileOutputStream(f2);
CipherInputStream cis;
Cipher desciph = Cipher.getInstance("DES");
System.out.println("Cipher-Objekt erzeugt");
cis = new CipherInputStream(fis, desciph);
SecretKey desKey;
// Lesen und Signieren
FileInputStream fi = new FileInputStream("mykeystore");
KeyStore ks = KeyStore.getInstance("JKS","SUN");
char [] passwd1 = {'r','p','l','a','c','d','1'};
ks.load(fi,passwd1);
char [] passwd2 = {'r','p','l','a','c','a','1'};
Key priv = ks.getKey("bel",passwd2);
Signature dsa = Signature.getInstance("DSA","SUN");
dsa.initSign((PrivateKey)priv);
FileOutputStream mdfo = new FileOutputStream("beleg01_sig.dat");
int siz = (int) f1.length();
int z = 0;
byte x =(byte)fis.read();
while(z < siz){
dsa.update(x);
mdfo.write(x);
z++;
x =(byte)fis.read();
}
byte [] sig = dsa.sign();
fis.close();
System.out.println("------- Datei gelesen und signiert -------");
mdfo.write((byte)'S');
mdfo.write((byte)'I');
mdfo.write((byte)'G');
System.out.println("------- SIG geschrieben -------");
mdfo.write(sig);
mdfo.close();
System.out.println("------- signierte Datei geschrieben -------");
f1 = new File("beleg01_sig.dat");
fis = new FileInputStream(f1);
cis = new CipherInputStream(fis, desciph);
kfis = new FileInputStream(
"i:/prakt/fritzsch/Sicherheit/chiffkey.dat");
ObjectInputStream keyin =
new ObjectInputStream(kfis);
desKey = (SecretKey)keyin.readObject();
System.out.println("Key deserialisiert");
desciph.init(Cipher.ENCRYPT_MODE,desKey);
byte [] b = new byte [8];
int i = cis.read(b);
while(i != -1){
fos.write(b,0,i);
i = cis.read(b);
}
fos.close();
System.out.println("Dateien lesen/schreiben beendet");
}
catch(Exception e){
System.err.println("Error:"+ e);
}
}
}
import
import
import
import
import
java.security.*;
java.security.cert.*;
java.io.*;
java.util.*;
javax.crypto.*;
public class Beleg01PruefS{
public static void main(String args []){
// Arbeitsverzeichnis: htw4711
// Aufruf:
java Beleg01PruefS htw4711
try {
// Zeitpunkt der Ueberpruefung registrieren ------------System.out.println("Beleg geprueft:");
System.out.println((new Date()).toLocaleString());
// Provider SunJCE eintragen ---------------------------Provider sunJCE = new com.sun.crypto.provider.SunJCE();
Security.addProvider(sunJCE);
// Certificate löschen (auch wenn nicht vorhanden )---------String command1 = "keytool -delete " +
" -alias " + args[0] +
" -keystore i:/Prakt/fritzsch/Sicherheit/mykeystore“ +
" -storepass rplacd1";
System.out.println("-- invoke: ");
System.out.println("
" + command1);
Runtime rt1 = Runtime.getRuntime();
Process p1 = rt1.exec(command1);
p1.waitFor();
System.out.println("
... beendet mit RC="+ p1.exitValue());
// Certificate importieren ----------------------------------System.out.println("-- Zertifikat importieren ");
String command = "keytool -import "+
" -alias " + args[0] +
" -file "+ args[0] + ".cer"+
//" -keystore c:/workstation/IS/mykeystore"+
" -keystore i:/Prakt/fritzsch/Sicherheit/mykeystore"+
" -storepass rplacd1";
System.out.println("-- invoke: ");
System.out.println("
" + command);
Runtime rt = Runtime.getRuntime();
Process p = rt.exec(command);
String ss = "y\n";
p.getOutputStream().write(ss.getBytes());
p.getOutputStream().close();
p.waitFor();
System.out.println("
... beendet mit RC="+ p.exitValue());
// Keystore-Datei lesen -----------------------------------KeyStore ks = KeyStore.getInstance("JKS","SUN");
char [] passwd1 = {'r','p','l','a','c','d','1'};
FileInputStream fi =
new FileInputStream(
"i:/Prakt/fritzsch/Sicherheit/mykeystore");
ks.load(fi,passwd1);
// Message-Digest prüfen ----------------------------------MessageDigest md = MessageDigest.getInstance("MD5");
FileInputStream fius =
new FileInputStream("belegis.dat");
byte [] org = {1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,
1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,
1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,
1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,
1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,1};
int i = 0;
org[i]=(byte)fius.read();
while (org[i]!=-1){
md.update(org[i]);
i=i+1;
org[i]=(byte)fius.read();
}
fius.close();
FileInputStream fimd = new FileInputStream("belegis_MD5.dat");
byte [] dig = {1,1,1,1,5,1,1,1,1,5,1,1,1,1,5,1,0};
int j = 0;
dig[j] = (byte)fimd.read();
while (j<15){
j=j+1;
dig[j] = (byte)fimd.read();
}
fimd.close();
byte [] medi =md.digest();
boolean vergleich=true;
for (int k = 0; k<16; k++)
if(dig[k]!=medi[k])
vergleich=false;
System.out.println("-- Vergleich Message Digest:" + vergleich);
// Sitzungsschlüssel deserialisieren -----------------------FileInputStream kfis = new FileInputStream(
"i:/Prakt/fritzsch/Sicherheit/chiffkey.dat");
ObjectInputStream keyin = new ObjectInputStream(kfis);
SecretKey desKey=(SecretKey)keyin.readObject();
System.out.println("-- Sitzungsschluessel deserialisiert");
// Datei chiffretext.dat dechiffrieren und ----------------// in belegis_zwi.dat ablegen
FileInputStream fis = new FileInputStream("chiffretext.dat");
FileOutputStream fos =
new FileOutputStream("belegis_zwi.dat");
CipherInputStream cis;
Cipher desciph = Cipher.getInstance("DES/ECB/PKCS5Padding");
cis = new CipherInputStream(fis,desciph);
desciph.init(Cipher.DECRYPT_MODE,desKey);
byte [] ba = new byte [1];
int iii = cis.read(ba);
while (iii != -1){
fos.write(ba,0,iii);
iii = cis.read(ba);
}
fos.close();
fis.close();
System.out.println("-- Dechiffrierung erfolgreich");
// öffentlichen Schlüssel aus Certif. extrahieren ----------java.security.cert.X509Certificate cl =
(java.security.cert.X509Certificate) ks.getCertificate(args[0]);
PublicKey pub = cl.getPublicKey();
System.out.println("-- oeffentlicher Schluessel extrahiert");
// Gültigkeitsdauer des Zertifikates überprüfen -------------Date bef = cl.getNotBefore();
Date aft = cl.getNotAfter();
System.out.println("-- Zertifikat ist gueltig");
System.out.println("
vom: " + bef.toLocaleString());
System.out.println("
bis: " + aft.toLocaleString());
// Signatur-Objekt zum Prüfen initialisieren ----------------Signature dsa = Signature.getInstance("DSA");
dsa.initVerify(pub);
// Zwischendatei belegis_zwi.dat lesen ----------------------File gesamtFile = new File("belegis_zwi.dat");
int sizef = (int)gesamtFile.length();
fis = new FileInputStream(gesamtFile);
byte b = (byte)fis.read();
sizef--;
byte c = (byte)fis.read();
sizef--;
byte d = (byte)fis.read();
while ((d != -1)&&((b !='S')||(c != 'I')||(d !='G'))){
sizef--;
dsa.update(b);
b=c;
c=d;
d=(byte)fis.read();
}
sizef--;
// Signatur lesen -----------------------------------------System.out.println("Laenge der Signatur: "+sizef);
byte [] sig = new byte[sizef];
int ii = 0;
byte s = (byte)fis.read();
while (ii < sizef){
sig[ii] = s;
ii++;
s = (byte)fis.read();
}
fis.close();
System.out.println("-- Signatur gelesen");
// Signatur pruefen ----------------------------------------boolean verifies = dsa.verify(sig);
System.out.println("-- Signatur verifiziert:"+verifies);
System.out.println("-- Ende");
}
catch(Exception e){
System.out.println("error:"+e);
}
}
}
import
import
import
import
import
java.applet.Applet;
java.awt.*;
java.awt.event.*;
java.io.*;
javax.swing.*;
import List;
public class HanoiVisual extends JApplet implements ActionListener{
JPanel jPanel0= new JPanel();
JPanel jPanel1= new JPanel();
JPanel jPanel2 = new JPanel();
JPanel jPanel3 = new JPanel();
JPanel jPanel4 = new JPanel();
JButton popbutton = new JButton("pop");
JButton pushbutton = new JButton("push");
JButton emptybutton = new JButton("emptyStack");
JButton runbutton = new JButton("run");
JButton stopbutton = new JButton("stop");
JPanel buttonPanel = new JPanel();
VisObject vo1 = new VisObject(0, jPanel1);
VisObject vo2 = new VisObject(0, jPanel2);
VisObject vo3 = new VisObject(0, jPanel3);
public void init(){
try{
UIManager.setLookAndFeel(
UIManager.getCrossPlatformLookAndFeelClassName());
Container contentPane= getContentPane();
contentPane.setBackground(Color.white);
jPanel0.setBorder(BorderFactory.createEtchedBorder());
jPanel0.setLayout(new GridLayout(1,3,5,10));//3 Spalten
jPanel1.setBorder(BorderFactory.createEtchedBorder());
jPanel1.setLayout(new GridLayout(10,1,5,0));//10 Zeilen
for (int j=0;j<10;j++){
jPanel4= (JPanel)jPanel1.add(new MyJPanelInit(),j);
}
jPanel2.setBorder(BorderFactory.createEtchedBorder());
jPanel2.setLayout(new GridLayout(10,1,5,0));//10 Zeilen
for (int j=0;j<10;j++){
jPanel4= (JPanel)jPanel2.add(new MyJPanelInit(),j);
}
jPanel3.setBorder(BorderFactory.createEtchedBorder());
jPanel3.setLayout(new GridLayout(10,1,5,0));//10 Zeilen
for (int j=0;j<10;j++){
jPanel4= (JPanel)jPanel3.add(new MyJPanelInit(),j);
}
jPanel0.add(jPanel1);
jPanel0.add(jPanel2);
jPanel0.add(jPanel3);
contentPane.add("Center",jPanel0);
pushbutton.addActionListener(this);
buttonPanel.add(pushbutton);
popbutton.addActionListener(this);
buttonPanel.add(popbutton);
emptybutton.addActionListener(this);
buttonPanel.add(emptybutton);
runbutton.addActionListener(this);
buttonPanel.add(runbutton);
stopbutton.addActionListener(this);
buttonPanel.add(stopbutton);
contentPane.add("South",buttonPanel);
validate();
}catch(Exception e){ }
}
public void actionPerformed(ActionEvent evt){
if(evt.getActionCommand().equals("pop")){
MyJPanel y = popvis(vo1);
}
if(evt.getActionCommand().equals("push")){
pushvis(vo1,new MyJPanel(vo1.i+1));
}
if(evt.getActionCommand().equals("emptyStack")){
vo1.i=0;
jPanel1.removeAll();
for (int j=0;j<10;j++){
jPanel4= (JPanel)jPanel1.add(new MyJPanelInit(),j);
}
vo2.i=0;
jPanel2.removeAll();
for (int j=0;j<10;j++){
jPanel4= (JPanel)jPanel2.add(new MyJPanelInit(),j);
}
vo3.i=0;
jPanel3.removeAll();
for (int j=0;j<10;j++){
jPanel4= (JPanel)jPanel3.add(new MyJPanelInit(),j);
}
paint(getGraphics());
}
if(evt.getActionCommand().equals("run")){
hanoiinit();
validate();
}
if(evt.getActionCommand().equals("stop")){
stop();
init();
}
}
public void pushvis(VisObject p,MyJPanel x){
p.i++;
p.jP.remove(10-p.i);
jPanel4= (JPanel)p.jP.add(x,10-p.i);
validate();
paint(getGraphics());
}
public MyJPanel popvis(VisObject p){
MyJPanel x = (MyJPanel)p.jP.getComponent(10-p.i);
p.jP.remove(10-p.i);
jPanel4= (JPanel)p.jP.add(new MyJPanelInit(),10-p.i);
validate();
paint(getGraphics());
p.i--;
return x;
}
public void hanoiinit(){
List a = new List();
a = a.cons(vo1);
for (int j=0;j<vo1.i;j++)
a= a.cons(new Integer(vo1.i-j));
a=a.reverse();
a.princ();
List b = new List();
b = b.cons(vo2);
b.princ();
List c = new List();
c = c.cons(vo3);
c.princ();
hanoi(a,b,c);
}
public void hanoi(List a, List b, List c){
if (a.cdr().cdr().nullp())
move(a, b);
else {
hanoi(a.cdr().cdr().cons(a.car()),c,b);
validate();
move(a, b);
validate();
hanoi(c.append(a.cdr().cdr()),b,(new List()).cons(a.car()));
validate();
}
}
public void move(List a, List b){
MyJPanel x = popvis((VisObject)a.car());
validate();
pushvis((VisObject)b.car(),x);
validate();
try{
Thread.currentThread().sleep(1200);
validate();
}
catch(InterruptedException e){
}
}
public void paint(Graphics g){
getContentPane().paintAll(g);
}
}
class MyJPanel extends JPanel{
public MyJPanel(int i){
super();
this.setBackground(Color.black);
this.add(new Scheibe(i));
}
}
// cyan
class Scheibe extends JPanel{
public Scheibe(int i){
super();
int x = this.getWidth();
this.setBorder(BorderFactory.createEmptyBorder(
0,x+93-10*i,0,x+93-10*i));
this.setBackground(Color.yellow);
this.add(new JLabel(String.valueOf(i)));
}
}
class MyJPanelInit extends JPanel{
public MyJPanelInit(){
super();
this.setBackground(Color.black);
}
}
class VisObject {
public int i;
public JPanel jP;
public VisObject(int n, JPanel p){
i=n;
jP=p;
}
}