diff --git a/ss2011/it-sicherheit/Uebungen/RSA_Exercise_4373.java b/ss2011/it-sicherheit/Uebungen/RSA_Exercise_4373.java
new file mode 100644
index 00000000..7b9f31e3
--- /dev/null
+++ b/ss2011/it-sicherheit/Uebungen/RSA_Exercise_4373.java
@@ -0,0 +1,121 @@
+package src;
+import java.security.InvalidKeyException;
+import java.security.Key;
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.NoSuchAlgorithmException;
+import java.security.NoSuchProviderException;
+import java.security.PrivateKey;
+import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+
+import javax.crypto.Cipher;
+
+public class RSA_Exercise_4373 extends RSA_Basics implements RSA_ExerciseInterface{
+
+	private static String text="first exercise";
+	
+	private Key privatekey;
+	private Key publickey;
+	
+	
+	public Key getPrivate() {
+		return privatekey;
+	}
+	
+	public Key getPublic() {
+		return publickey;
+	}
+	
+	public void generateRSAKeypair() {
+		// Get a KeyPair Generator
+		KeyPairGenerator gen;
+		try {	gen = KeyPairGenerator.getInstance("RSA");}
+		catch (NoSuchAlgorithmException e) { 
+			//This should not be the case ;-)
+			privatekey 	= null;
+			publickey 	= null;
+			return;}
+		
+		//set to 1024bit
+		gen.initialize(1024);
+
+		//Generate the Pair
+		KeyPair keypair = gen.genKeyPair();
+
+		//Assign class vars
+		privatekey = keypair.getPrivate();
+		publickey  = keypair.getPublic();
+	}
+	
+	public String sign(String value, Key key) throws Exception
+	{
+		// Instance
+		Signature signature = Signature.getInstance("SHA1withRSA");
+		
+		signature.initSign((PrivateKey) key);		
+		signature.update(value.getBytes());		
+		return asHex(signature.sign());	
+	}
+	
+	public boolean verify(String value,String sigtoverify, Key key) throws NoSuchAlgorithmException, NoSuchProviderException, InvalidKeyException, SignatureException
+	{
+		// Instance
+		Signature signature = Signature.getInstance("SHA1withRSA");
+		
+		signature.initVerify((PublicKey) key);
+		signature.update(value.getBytes());
+		return signature.verify(asByteArray(sigtoverify));
+	}
+	
+	public String encrypt(String value, Key key) throws Exception
+	{
+		// Instance
+		Cipher cip = Cipher.getInstance("RSA");
+	
+		// Set mode + finalize
+		cip.init(Cipher.ENCRYPT_MODE, key);
+		return asHex(cip.doFinal(value.getBytes()));
+	}
+	
+	public String decrypt(String value, Key key) throws Exception
+	{
+		// Instance
+		Cipher cip = Cipher.getInstance("RSA");
+		
+		// Set mode + finalize
+		cip.init(Cipher.DECRYPT_MODE, key);
+		return new String(cip.doFinal(asByteArray(value)));
+	}
+	
+	
+	public static void main(String[] args) throws Exception
+	{
+		String output="";
+		
+		//Generate Instance
+		RSA_Exercise_4373 rsa=new RSA_Exercise_4373();
+		
+		//Generate new Keypair
+		rsa.generateRSAKeypair();
+		
+		String studid="4373"; //Please change me to your own four last digits of the student id
+		
+		//Signature Checks
+		output="Signature of "+text+" is:"+rsa.sign(studid+text,rsa.getPrivate())+"\n";
+		output+="The signature of "+text+" is :"+rsa.verify(studid+text, rsa.sign(studid+text,rsa.getPrivate()), rsa.getPublic())+"\n";
+		
+		output+="Ciphertext:" +rsa.encrypt(studid+text,rsa.getPublic())+"\n";
+		output+="Decrypted Text:"+rsa.decrypt(rsa.encrypt(studid+text,rsa.getPublic()),rsa.getPrivate())+"\n";
+		
+		System.out.println(output);
+		
+		// Write current Public and Private key for solution hand-in
+		writeData(rsa.getClass().getName(), rsa.getPrivate(), rsa.getPublic(),output);
+		
+	}
+	
+	
+	
+}
diff --git a/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_log b/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_log
new file mode 100644
index 00000000..8f1341f6
--- /dev/null
+++ b/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_log
@@ -0,0 +1,4 @@
+Signature of first exercise is:d2d9785e7c16021399a69f92f1066ff6f805ade1df0df15b31a4532fad491330110d24bfe55e95a646d3b83fcce838d747057ceb71d798fdc7d967ae972983c0d759f1742a5147a0afa6e66d4eeaa11a325df695af0139c32cb20fb166a379560d4e8e8a71b3ab113462770ccc94af12dd421e7e1fbf8aaffb6ab27e836172d0
+The signature of first exercise is :true
+Ciphertext:2db35f58e239adef275ceeaeb17917b1a64e1ae4787a446cf3c681125656f454e86b2d1cc982a804b723b56cc6d6b507b9020099b447ec70b6cd424051e719869351283b61ac35b23dc4a0ee4900f6280ab0368fe263ce32dde1ca269d6079605f88f44d0b55631fc98333e044e209a7b3c8e6ddec6fd239f2d59ad9ead01b1e
+Decrypted Text:4373first exercise
diff --git a/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_priv b/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_priv
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diff --git a/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_pub b/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_pub
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index 00000000..40331d16
Binary files /dev/null and b/ss2011/it-sicherheit/Uebungen/src.RSA_Exercise_4373_pub differ