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Cryptography & Java Internet Security 1Goals of Network Security 2Basic Cryptographic Concepts 3Java Security Concepts & Applets 4Java Cryptographic Architecture.

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Presentation on theme: "Cryptography & Java Internet Security 1Goals of Network Security 2Basic Cryptographic Concepts 3Java Security Concepts & Applets 4Java Cryptographic Architecture."— Presentation transcript:

1 Cryptography & Java Internet Security 1Goals of Network Security 2Basic Cryptographic Concepts 3Java Security Concepts & Applets 4Java Cryptographic Architecture (JCE) & Java Cryptographic Extension (JCE) 5An example: what students have to do...

2 1 Goals of Network Security 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) Security is multilateral !

3 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

4 Basics Cryptology = Cryptography + Crypto analysis Secret communication CryptographySteganography TranspositionSubstitution

5 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,...)

6 Crypto system M : plaintext space C : ciphertext space K : key space M : plaintext message C : ciphertext message K : key E : M × K C D : C × K M E ( M ) = C D ( C ) = M D K (E K ( M ) ) = M | M M E = Encrypt D = Decrypt

7 Message Digest = one way hash function w = h (x) Example: w = b x (mod m) Message Authentification Code (MAC) = hash function with secure key w = h (x, k)

8 symmetric encryption asymmetric encryption encryptdecrypt A B plaintext ciphertext Key generator k = secure key xxC(x) Random number k decryptencrypt A B plaintext ciphertext Key generator s = private key xxC(x) t = public key

9 Diffie-Hellman key exchange Public: g= 4, p=11 B Private key x B = 4 Public key y B = g x B mod p = 4 4 mod 11 = 256 mod 11 = 3 K = y A xB mod p = 9 4 mod 11 = 5 A Private key x A = 3 Public key y A = g x A mod p = 4 3 mod 11 = 64 mod 11 = 9 Session key K = y B xA mod p = 3 3 mod 11 = 5


11 X.509 Certificate version serial number Algorithm identifier Issuer (name of CA) Period of validity Subject (user name) Public key Signature (CA)

12 symmetric authentification asymmetric authentication (signature system) Generate MAC test MAC A B textText, testresult Text with authentific. Key generator k = secure key x, {true | false}xx, MAC Random number k signverify A B text Text with signatur + testresult Text with signature Key generator s = private key (sign) x,sig(x), {true | false} xx, sig(x) t = public key (verify)

13 3 Java: Security Concept & Applets 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 A security manager in the JVM controls access How an applet works and how it looks like

14 Java 1.0 Security Model

15 Java 1.1 Security Model

16 Java 1.2 Security Model

17 4 Java Cryptographic Architecture (JCA) & Java Cryptographic Extension (JCE) Design principle: Provider - Algorithm - Concept Classes: Identity Signer MessageDigest Signature Key KeyPair KeyPairGenerator KeyGenerator SecureRamdom KeyStore Certificate X509Certificate Cipher SUNMD5MessageDigest SHA1 XRSASignature DSA

18 5 An example: what students have to do... Task description for studentsTask description steps: 1give an applet rights to write a file belegis.dat on client 2generate a keypair and a self signed certificate (X.509) ; store the keypair in a keystore file and export certificate to a file 3write a Java-application that produces a MD5-Message Digest of file belegis.dat 4write 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 ): –file belegis.dat (load html-page) –the self signed certificate(use keytool) –the message digest(run program of step 3) –the chiffretext (run program of step 4)

19 Preparation Make available - applet - 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

20 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) Solutions 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 ResponseResponse to Solution

21 import*; import*; import*; 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); while(xx != -1){ md.update(xx); xx =(byte); } fi2.close(); System.out.println(" Datei gelesen ");

22 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); }

23 import*; import*; import*; import*; import*; import javax.crypto.*; import javax.crypto.spec.*; import 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 "+ " "); System.exit(8); } f1 = new File(args[0]); f2 = new File(args[1]);

24 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);

25 FileOutputStream mdfo = new FileOutputStream("beleg01_sig.dat"); int siz = (int) f1.length(); int z = 0; byte x =(byte); while(z < siz){ dsa.update(x); mdfo.write(x); z++; x =(byte); } 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 ");

26 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 =; while(i != -1){ fos.write(b,0,i); i =; } fos.close(); System.out.println("Dateien lesen/schreiben beendet"); } catch(Exception e){ System.err.println("Error:"+ e); }

27 import*; import*; import*; import java.util.*; import 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);

28 // 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());

29 // 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);

30 // 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}; int i = 0; org[i]=(byte); while (org[i]!=-1){ md.update(org[i]); i=i+1; org[i]=(byte); } 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); while (j<15){ j=j+1; dig[j] = (byte); } fimd.close();

31 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");

32 // 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 =; while (iii != -1){ fos.write(ba,0,iii); iii =; } fos.close(); fis.close(); System.out.println("-- Dechiffrierung erfolgreich"); // öffentlichen Schlüssel aus Certif. extrahieren cl = ( ks.getCertificate(args[0]); PublicKey pub = cl.getPublicKey(); System.out.println("-- oeffentlicher Schluessel extrahiert");

33 // 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);

34 // Zwischendatei belegis_zwi.dat lesen File gesamtFile = new File("belegis_zwi.dat"); int sizef = (int)gesamtFile.length(); fis = new FileInputStream(gesamtFile); byte b = (byte); sizef--; byte c = (byte); sizef--; byte d = (byte); while ((d != -1)&&((b !='S')||(c != 'I')||(d !='G'))){ sizef--; dsa.update(b); b=c; c=d; d=(byte); } sizef--;

35 // Signatur lesen System.out.println("Laenge der Signatur: "+sizef); byte [] sig = new byte[sizef]; int ii = 0; byte s = (byte); while (ii < sizef){ sig[ii] = s; ii++; s = (byte); } 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); }






41 import java.applet.Applet; import java.awt.*; import java.awt.event.*; import*; import 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);

42 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); }

43 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){ } }

44 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()); }

45 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; }

46 public void hanoiinit(){ List a = new List(); a = a.cons(vo1); for (int j=0;j

47 public void move(List a, List b){ MyJPanel x = popvis((VisObject); validate(); pushvis((VisObject),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(; // cyan this.add(new Scheibe(i)); }

48 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(; } class VisObject { public int i; public JPanel jP; public VisObject(int n, JPanel p){ i=n; jP=p; }

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