TU Wien:Verteilte Systeme UE (Rausch)/Gesammelte Test MC-Fragen

Info

Das sind alle MC-Fragen, die ich im informatik-forum so gefunden habe. Formatierung ist noch recht unschön, aber mal ein Anfang. Würde mich freuen, wenn ihr sie erweitert, jedoch bitte nur mit neue Fragen ;).

27.01.2023 - 4

Frage 1

In RMI for bootstrapping purposes you have to register with the RMI registry ...

• ☐ True
• ☒ False

Frage 2

In asymmetric cryptography, which key is used to decrypt a message?

• ☐ The sender's private key.
• ☒ The receiver's private key.
• ☐ The sender's public key.
• ☒ The receiver's public key.
• ☐ The shared secret key.

Frage 3

If an object is an instance of java.rmi.server.UnicastRemoteObject then it also implements java.io.Serializable.

• ☒ True
• ☐ False

Frage 4

Asymmetric cryptography: To make sure only the intended receiver can decrypt a message, it has to be encrypted with the sender's private key.

• ☐ True
• ☒ False

Frage 5

In asymmetric cryptography, which key is used to encrypt a message?

• ☐ The sender's private key.
• ☐ The receiver's private key.
• ☐ The sender's public key.
• ☒ The receiver's public key.
• ☐ The shared secret key.

Frage 6

A stub in RMI is the component responsible for:

• ☐ True
• ☒ False

Frage 7

Mark the correct answers concerning TCP and UDP Sockets in Java:

• ☒ True
• ☐ False

Frage 8

When a synchronized method is called in Java, a lock is obtained on:

• ☒ The object (this)
• ☐ The method
• ☐ The class
• The variables used in the method

Frage 9

Symmetric encryption techniques make us of key pairs (public and private key) to encrypt and decrypt messages:

• ☐ True
• ☒ False

Frage 10 (falsch)

Mark the correct answer(s) concerning concurrency and synchronization in Java:

Wählen Sie eine oder mehrere Antworten:

• ☒ If a java.util.HashMap is accessed only by retrieving it from a getter method, the HashMap can be made thread-safe by writing the synchronized keyword in front of that getter method.
• ☐ A java.util.HashMap may throw a ConcurrentModificationException even with perfectly proper synchronization.
• ☐ If a class is defined as synchronized (e.g., public synchronized class Foo) then all methods of this class are automatically thread safe.
• ☒ Adding the synchronized modifier to the method signature is effectively equivalent to enclosing the body of the method with a synchronized(this) {...} block.

Frage 11

Which statement(s) regarding security hold true:

• ☒ Data integrity refers to the fact that data must be reliable and accurate over its entire lifecycle.
• ☒ Data encryption is a common method of ensuring confidentiality.
• ☐ Data encryption is a common method of ensuring integrity.
• ☒ Confidentiality concerns with protecting sensitive information from disclosure to unauthorized parties.

Frage 12

Which statements about the startsecure handshake protocol implemented in Lab 2 are correct?

• ☒ Its purpose is to be guard against replay attacks (a once valid transmission is fraudulently repeated or delayed).
• ☐ During the handshake, the sender uses the receiver's private key for encryption.
• ☒ The initial handshake (encrypted via RSA) is used to safely exchange the AES key.

27.01.2023 - 3

Insgesamt 20 Fragen. Habe nur richtige Fragen geposted. LG Big Schnozer

Frage 1

Which statement(s) hold true regarding cryptography:

• ☐ Asymmetric cryptography is significantly faster than symmetric cryptography.
• ☐ If possible, asymmetric cryptography should always be preferred over symmetric cryptography.
• ☒ Asymmetric cryptography can be either used for encryption or signing.
• ☒ The exchange of a common key bears a potential risk for symmetric cryptography.

Frage 2

Mark the correct answers regarding data and multithreading:

• ☒ If a Java program with multiple threads runs on a single processor (CPU), the operations of all concurrent threads are executed sequentially. The execution order of these operations is non-deterministic.
• ☐ The JVM automatically performs synchronization where multiple threads try to manipulate data.
• ☐ Objects that are passed into other threads are automatically passed as deep copies to ensure thread safety.
• ☒ The programmer has to ensure that concurrent access to data by multiple threads is synchronized.

Frage 3

Which statements about Java RMI are correct?

• ☒ It is an API to hide network communication from the programmer.
• ☒ It allows programs running in different Java Virtual Machines to communicate.
• ☐ It is the object-oriented equivalent of TCP.
• ☐ It simplifies data exchange between programs written in different languages.

Frage 4

Which procedure is used to establish a TCP connection?

• ☐ Request/response messaging
• ☐ Two-way handshake
• ☐ TCP does not require connection establishment
• ☒ Three-way handshake

Frage 5

Which statements about symmetric key encryption are correct?

• ☐ RSA is an example of symmetric encryption.
• ☒ AES is an example of symmetric encryption.
• ☒ The same key is used for encryption and decryption.

Frage 6

In order to establish a connection with a server socket, is it required to manually specify the local port number of the Java client socket?

• ☐ Yes, the local port has to be specified upon creation of the client socket.
• ☒ No, the underlying platform will choose a free port at random.
• ☐ No, the client socket will automatically negotiate a port number with the server socket via the handshake protocol.

Frage 7

Which statements about Base64 encoding are correct?

• ☐ Base64 is a hash-based encoding scheme.
• ☐ Base64 encoded messages are less vulnerable to man-in-the-middle attacks.
• ☒ Encoding messages with Base64 increases their data size.
• ☒ Base64 encoding is necessary to send binary data over plain text channels.

Frage 8

Asymmetric cryptography: To make sure only the intended receiver can decrypt a message, it has to be encrypted with the receiver's public key.

• ☒ Wahr
• ☐ Falsch

Frage 9

Which properties does the DMTP (DSLab Message Transfer Protocol) protocol have?

• ☐ Binary
• ☒ Plain-text
• ☐ Asynchronous
• ☒ Synchronous

Frage 10

Which types of objects can be passed as parameters to a method defined by an RMI remote object (suppose both client and server have access to the same code).

• ☒ Any primitive data type.
• ☐ Any object that does not use other complex types (like collections).
• ☒ Any fully serializable object.
• ☐ Any object that only has primitive members.
• ☒ References to other remote objects.

Frage 11

To generate a Hash-based message authentication code (HMAC) one needs:

• ☒ A shared secret key.
• ☐ A public and private key.
• ☐ Only an appropriate hash function.

Frage 12

Imagine you want to execute Java code in a new Thread. One possibility is to write a class MyExecutable that implements the interface java.lang.Executable and to create a new Thread that executes the code in MyExecutable.

• ☐ Wahr
• ☒ Falsch

Frage 13

Which statements about UDP are correct?

• ☐ UDP re-transmits lost packages.
• ☒ UDP is a connectionless protocol.
• ☐ UDP guarantees that packets are received in the order they were sent.
• ☒ UDP is useful when the loss of individual packets is unimportant.

27.01.2023 - 2

Frage 2

Which statement(s) hold true for Message Authentication Codes (MAC):

• ☐ A message is encrypted with a shared key before sending and the resulting ciphertext is transferred alongside with the original message.
• ☐ A message is encrypted and hashed before sending and the resulting hash is transferred alongside with the original message.
• ☒ A message and a shared secret are hashed before sending and the resulting hash is transferred alongside with the original message.
• ☐ A message and the public key of the authenticated receiver are hashed before sending and the resulting hash is transferred alongside with the original message.

Frage 4

Assume a remote interface MyRemoteA and another remote interface MyRemoteB that declares a method with the signature void foo(MyRemoteA a) throws RemoteException;. Is the method signature of foo a valid signature for an RMI remote method?

• ☒ True
• ☐ False

Frage 5

Which properties does the DMTP (DSLab Message Transfer Protocol) protocol have?

• ☐ Binary
• ☒ Plain-text
• ☐ Asynchronous
• ☒ Synchronous

Frage 6

Which statements about symmetric key encryption are correct?

• ☐ RSA is an example of symmetric encryption.
• ☒ AES is an example of symmetric encryption.
• ☒ The same key is used for encryption and decryption.

Frage 7

Asymmetric cryptography: To make sure only the intended receiver can decrypt a message, it has to be encrypted with the receiver's public key.

• ☒ True
• ☐ False

Frage 9

Which statements about Java RMI are correct?

• ☒ It allows programs running in different Java Virtual Machines to communicate.
• ☐ It is the object-oriented equivalent of TCP.
• ☒ It is an API to hide network communication from the programmer.
• ☐ It simplifies data exchange between programs written in different languages.

Frage 10

What type of service does TCP provide? Tick all that apply.

• ☒ reliable
• ☐ unreliable
• ☒ connection-oriented
• ☐ connection-less

Frage 11

Which types of exceptions can be used in the throws clause of remote object methods in RMI?

• ☐ Only exceptions that extend from java.rmi.RemoteException.
• ☒ Any exception that extends java.lang.Exception.
• ☐ Only exceptions that extend from java.lang.RuntimeException.
• ☐ RMI does not support custom exceptions.

Frage 12

Consider the following code that reads from a network socket:

           BufferedReader reader = new BufferedReader(...);
           try {
               String line = reader.readLine();
               System.out.println(line);
           } catch(InterruptedException e) {
               System.out.println("interrupted");
           }

Suppose the underlying socket is waiting on new data, but the executing thread is interrupted usingThread.interrupt(), what happens?

• ☒ Nothing, readLine() continues to block.
• ☐ null is printed to System.out and the method exits.
• ☐ interrupted is printed to System.out and the method exits.

Frage 13

What happens when the shutdown method of java.util.concurrent.ExecutorService is called?

• ☐ All threads submitted to the executor are terminated.
• ☐ The thread running the executor is terminated.
• ☒ The executor stops accepting new submit requests.
• ☐ The method blocks until all threads submitted to the executor have finished.

Frage 14

Asymmetric cryptography: The only way to encrypt a message is to use the public key, while the private key can only be used for decryption.

• ☒ False
• ☐ True

Frage 15

Which statement(s) hold true regarding cryptography:

• ☐ Asymmetric cryptography is significantly faster than symmetric cryptography.
• ☐ If possible, asymmetric cryptography should always be preferred over symmetric cryptography.
• ☒ Asymmetric cryptography can be either used for encryption or signing.
• ☒ The exchange of a common key bears a potential risk for symmetric cryptography.

Frage 16

• ☒ Any primitive data type.
• ☐ Any object that does not use other complex types (like collections).
• ☒ Any fully serializable object.
• ☐ Any object that only has primitive members.
• ☒ References to other remote objects.

Frage 17

What are the benefits of using Base64 encoding?

• ☐ The security is enhanced as the data is additionally encrypted with Base64.
• ☒ It is possible to transmit any kind of data as a text string.
• ☐ The data throughput is increased because of the higher bit-rate of Base64.
• ☒ Control characters are converted to printable ASCII characters.

Frage 18

If a method with the signature synchronized void doWork() {...} is accessed by two different threads on the same object instance, only one of the threads can execute at a time.

• ☒ True
• ☐ False

Frage 19

To establish a bidirectional communication between a server and a client through Java sockets, how many sockets and streams do you need at least on each side?

• ☒ 1 socket, 1 output stream and 1 input stream on each side (2 sockets, 4 streams in total on both sides).
• ☐ 2 sockets per side, each with 1 output stream and 1 input stream (4 sockets, 8 streams in total on both sides).
• ☐ 1 socket with 1 output stream plus 1 socket with 1 input stream, on each side (4 sockets, 4 streams in total on both sides).

Frage 20

If two hosts are communicating via UDP, both sides have to use the same port number for the UDP communication.

• ☒ False
• ☐ True

27.01.2023 - 1

Es kamen ähnliche Fragen wie im Vorjahr, hier sind weitere Fragen, die noch gestellt worden sind:

Frage 1

If a method with the signature synchronized void doWork() {...} is accessed by two different threads on the same object instance, only one of the threads can execute at a time.

• ☒ Wahr
• ☐ Falsch

Frage 2

When a synchronized method is called in Java, a lock is obtained on:

• ☒ The object (this)
• ☐ The method
• ☐ The class
• ☐ The variables used in the method

Frage 3

RSA is an example of a symmetric encryption protocol.

• ☐ Wahr
• ☒ Falsch

Frage 4

To generate a Hash-based message authentication code (HMAC) one needs:

• ☒ A shared secret key
• ☐ A public and private key
• ☐ Only an appropriate hash function.

Frage 5

What happens when the shutdown method of java.util.concurrent.ExecutorService is called?

• ☐ All threads submitted to the executor are terminated.
• ☐ The thread running the executor is terminated.
• ☐ The executor stops accepting new submit requests.
• ☐ The method blocks until all threads submitted to the executor have finished.

Frage 6

Which statements about Java RMI are correct?

• ☒ It allows programs running in different Java Virtual Machines to communicate.
• ☐ It is the object-oriented equivalent of TCP.
• ☒ It is an API to hide network communication form the programmer.
• ☐ It simplifies data exchange between programs written in different languages.

Frage 7In asymmetric cryptography, which key is used to decrypt a message?

• ☐ The sender's private key.
• ☒ The receiver's private key.
• ☐ The sender's public key.
• ☐ The receiver's public key.
• ☐ The shared secret key.

Frage 8

Which types of exceptions can be used in the throws clause of remote object methods in RMI?

• ☐ Only exceptions that extend from java.rmi.RemoteException .
• ☐ Any exception that extends java.lang.Exception .
• ☐ Only exceptions that extend from java.lang.RuntimeException .
• ☐ RMI does not support custom exceptions.

Frage 9

Consider the following code that reads from a network socket:

 BufferedReader reader = new BufferedReader(...);

while(!Thread.interrupted()) {

    String line = reader.readLine();

    System.out.println(line);

}

Suppose the underlying socket is waiting on new data, but the executing thread is interrupted using Thread.interrupt(), what happens?

• ☐ null is printed on System.out and then the loop terminates.
• ☒ Nothing, readLine() continues to bock.
• ☐ An InterruptedException is thrown and the method exits.

Frage 10

Consider the following code that reads from a network socket:

 BufferedReader reader = new BufferedReader(...);

try{

    String line = reader.readLine();

    System.out.println(line);

} catch(InterruptedException e) {

    System.out.println("interrupted");

}

Suppose the underlying socket is waiting on new data, but the executing thread is interrupted using Thread.interrupt(), what happens?

• ☐ null is printed on System.out and the method exits.
• ☒ Nothing, readLine() continues to bock.
• ☒ interrputed is printed to System.out and the method exits.

Frage 11

Invocations to remote objects via RMI are thread safe.

• ☐ Wahr
• ☒ Falsch

Frage 12

Which procedure is used to establish a TCP connection?

• ☐ Request/response messaging
• ☐ Two-way handshake
• ☒ Three-way handshake
• ☐TCP does not require connection establishment

Frage 13

What is true about the challenge-respones authentication protocol (as used in the Lab):

• ☒ Its purpose is to be safe against reply attacks (a once valid transmission is fraudulently repeated or delayed).
• ☐ During the handshake, the sender uses the receiver's private key for encryption.
• ☒ The initial handshake (encrypted via RSA) is used to safely exchange the AES keys.

Frage 14

Assume a remote interface o MyRemoteA and another remote interface MyRemoteB that declares a method with the signature void foo(MyRemoteA a) throws RemoteException; . Is the method signature of foo a valid signature for an RMI remote method?

• ☒ Wahr
• ☐ Falsch

Frage 15

Which statement(s) hold true for Message Authentication Codes (MAC):

• ☐ A message is encrypted with a shared key before sending and the resulting ciphertext is transferred alongside with the original message.
• ☐ A message is encrypted and hashed before sending and the resulting hash is transferrred alongside with the original message.
• ☒ A message and a shared secret are hashed before sending and the resulting hash is transferred alongside with the original message.
• ☐ A message and the public key of the authenticated receiver are hashed before sending and the resulting hash is transferred alongside with the original message.

Frage 16

Asymmetric cryptography: The only way to encrypt a message is to use the pubic key, while the private key can only be used for decryption.

• ☐ Wahr
• ☒ Falsch

Frage 17

Java RMi communication is encrypted

• ☐ Wahr
• ☒ Falsch

Frage 18

To establish a bidirectional communication between a server and a client through Java sockets, how many sockets and streams do you need at least on each side?

• ☒ 1 socket, 1 output stream and 1 input stream on each side (2 sockets, 4 streams in total on both sides).
• ☐ 2 sockets per side, with 1 output stream and 1 input stream (4 sockets, 8 streams in total on both sides).
• ☐ 1 socket with 1 ouput stream plus 1 socket with 1 input stream, on each side (4 sockets, 4 streams in total on both sides).

Frage 19

Which procedure is used to establish a UDP connection?

• ☐ Request/response messaging
• ☐ Two-way handshake
• ☐ Three-way handshake
• ☒ UDP does not require connection establishment

28.01.2022

Frage 1

Which statements about UDP are correct?

• ☐ It is the object-oriented equivalent of remote procedure call (RPC).
• ☐ It relies on the publish/subscribe messaging pattern.
• ☐ It simplifies the coordination of multi-threaded programs.
• ☒ It simplifies data exchange between Java programs.

Frage 2

Which statements about Java RMI are correct?

• ☒ It is the object-oriented equivalent of remote procedure call (RPC).
• ☐ It relies on the publish/subscribe messaging pattern.
• ☐ It simplifies the coordination of multi-threaded programs.
• ☒ It simplifies data exchange between Java programs.

Frage 3

Which types of connections does java.net.ServerSocket accept?

• ☐ UDP connections.
• ☒ TCP connections.
• ☐ TCP and UDP connections.

Frage 4

What are valid methods to enable a thread-safe for-each loop iteration over a List myList1? Hint: consider the case that a second thread attempts to add an item to myList1 while the loop is still active.

• ☐ Creating a thread-safe wrapper with Collections.synchronizedList(myList1).
• ☐ There is no need for synchronization. An iteration is only a series of read-accesses.
• ☒ Creating a synchronized block that uses myList1 as lock-object.

Frage 5

Which statements about Base64 encoding are correct?

• ☐ Base64 adds a layer of security.
• ☒ Base64 translates binary data to ASCII printable characters.
• ☐ Base64 is necessary to send binary data over TCP channels.
• ☒ Base64 encoded channels exhibit higher network traffic.

Frage 6

Similar to java.net.Socket, the input/output streams of java.net.DatagramSocket have to be closed.

• ☐ Wahr
• ☒ Falsch

Frage 7

Which statement(s) hold true for Message Authentication Codes (MAC):

• ☐ A message is encrypted with a shared key before sending and the resulting ciphertext is transferred alongside with the original message.
• ☐ A message is encrypted and hashed before sending and the resulting hash is transferred alongside with the original message.
• ☒ A message and a shared secret are hashed before sending and the resulting hash is transferred alongside with the original message.
• ☐ A message and the public key of the authenticated receiver are hashed before sending and the resulting hash is transferred alongside with the original message.

Frage 8

Which of these code snippets are valid ways of implementing a thread-safe, consistent, and atomic in-memory ID generator? Wählen Sie eine oder mehrere Antworten:

• ☐ A:

class IdGenerator {
    int id = 0;

    int next() {
    id = id + 1;
    return id;
    }
}

• ☐ B:

class IdGenerator {
    int id = 0;

    int next() {
    return ++id;
    }
}

• ☒ C:

class IdGenerator {
    AtomicInteger id = new AtomicInteger();

    int next() {
    return id.incrementAndGet();
    }
}

• ☒ D:

class IdGenerator {
    int id = 0;

    int synchronized next() {
    return ++id;
    }
}

Frage 9

Which statement(s) hold true regarding cryptography:

• ☐ Asymmetric cryptography is significantly faster than symmetric cryptography.
• ☐ If possible, asymmetric cryptography should always be preferred over symmetric cryptography.
• ☒ Asymmetric cryptography can be either used for encryption or signing.
• ☒ The exchange of a common key bears a potential risk for symmetric cryptography.

Frage 10

Java RMI communication is encrypted.

• ☐ Wahr
• ☒ Falsch

Frage 11

Which statements about symmetric key encryption are correct?

• ☐ RSA is an example of symmetric encryption.
• ☒ AES is an example of symmetric encryption.
• ☒ The same key is used for encryption and decryption.

Frage 12

What happens when the close() method of a ServerSocket is called?

• ☐ All socket connections that were accepted by the ServerSocket are closed.
• ☒ The ServerSocket stops listening to new connection requests.
• ☐ The connected clients receive an exception that the ServerSocket was closed.

Frage 13

Asymmetric cryptography: The only way to encrypt a message is to use the public key, while the private key can only be used for decryption.

• ☐ Wahr
• ☒ Falsch

Frage 14

Which statements about TCP are correct?

• ☒ TCP automatically re-transmits lost packages.
• ☐ TCP is a connectionless protocol.
• ☒ TCP guarantees that packets are received in the order they were sent.
• ☐ TCP is useful when the loss of individual packets is unimportant.

Frage 15

Which types of objects can be passed as parameters to a method defined by an RMI remote object (suppose both client and server have access to the same code).

• ☒ Any primitive data type.
• ☐ Any object that does not use other complex types (like collections).
• ☒ Any fully serializable object.
• ☐ Any object that only has primitive members.
• ☒ References to other remote objects.

Frage 16

Consider the following class:

 class Worker {

    void synchronized foo() { /* ... */ }

    void synchronized bar() { /* ... */ }

}

Suppose two threads T1 and T2 call the same object Worker worker = new Worker(), but T1 calls worker.foo() and T2 calls worker.bar(). What happens?

• ☒ T1 has to wait for T2 to finish.
• ☐ T1 and T2 execute in parallel.

Frage 17

Which properties does the DMTP (DSLab Message Transfer Protocol) protocol have?

• ☐ Binary
• ☒ Plain-text
• ☐ Asynchronous
• ☒ Synchronous

Frage 18

Which properties does the DMAP (DSLab Message Access Protocol) protocol have?

• ☐ Stateless
• ☒ Plain-text
• ☒ Stateful
• ☐ Binary

Frage 19

How can you make an object which implements java.rmi.Remote remotely accessible through RMI?

• ☒ I let its class extend java.rmi.remote.UnicastRemoteObject.
• ☐ It is already remotely accessible, because of the implemented java.rmi.Remote interface.
• ☒ I use the static exportObject method of java.rmi.remote.UnicastRemoteObject.
• ☐ It is sufficient to bind the object in the RMI Registry.

Frage 20

In order to establish a connection with a server socket, is it required to manually specify the local port number of the Java client socket?

• ☐ Yes, the local port has to be specified upon creation of the client socket.
• ☒ No, the underlying platform will choose a free port at random.
• ☐ No, the client socket will automatically negotiate a port number with the server socket via the handshake protocol.

23.01.2020

Es waren ziemlich viele neue Fragen.

• Kann ein TCP und UDP Server mit dem gleichen Port gestartet werden?
• TCP ist
  • reliable
  • unreliable
  • connection-oriented
  • connection-less
• DMAP ist
  • stateless
  • statefull
  • ...
  • ...
• Frage bzgl. Kosten rekursive vs. iterative name resolution
• RMI STUB ist verantwortlich für
  • client-side-communication
  • server-side-communication
• Base64 ist
  • hash-basiert
  • ...
  • ...
  • ...

21.01.2015

Die Fragen, die unten stehen, decken ziemlich alles ab, was heuer gekommen ist.

• Objekte die Remote implementieren werden bei RMI via call by value, elementare Typen und Objekte die Serializable implementieren via call by reference übertragen. - Falsch, genau umgekehrt.

• Wenn man eine eigene Klasse MyExecutable hat kann man diese in einem Thread ausführen wenn sie das Executable-Interface implementiert. - Falsch, es gibt kein Executable Interface

22.01.2014

• Muss ein DatagramSocket wie ein normales Socket mit close() geschlossen werden? -> Ja

23.01.2013

• Im Zuge des TCP Verbindungsaufbaues zweier Endpunkte wird ein 3-Wege-Handshake gemacht. Richtig
• Ein Objekt wird remotely Accessible, wenn... (richtig ist: entweder erben von UnicastRemoteObjekt oder auf das Objekt müsste UnicastRemoteObject.exportObject(Remote obj, int port) angewandt werden.)
• Wird eine Nachricht über UDP versandt, dann verwenden Sender und Empfänger denselben Port. Richtig (edit 20150126 - es muss nicht der gleiche sein, kann aber)
• Kommunizieren (senden und erhalten) Client und Server miteinander via TCP, dann gibt es pro Partei:
  • 1 Socket und 2 Streams (Richtig)
  • 2 Sockets und 4 Streams
  • 1 ServerSocket, einen Socket und 8 Streams
• Beim Aufruf einer entfernten Methode wird ein Argument übertragen:
  • Sofern das Argument ein primitiver Datentyp ist, dann wird es copy be refernce übertragen. Falsch (s. [1] Abschnitt "Passing Objects in RMI")
• Es gibt eine remotly Accessible function, die eine Datenstruktur (Container) enthält. 2 Caller rufen zur selben Zeit die Funktion auf. Caller1 iteriert lesend über die Datenstruktur, während Caller2 noch ein Element an die Datenstruktur dranhängt: Damit es zu keinen Synchronizationsproblemen kommt, muss:
  • die Funktion in einen synchronized{} Block getan werden (Richtig)
  • ...
  • ...
• Bei asymmetrischer Verschlüsselung sendet der Sender die Nachricht verschlüsselt mittels des public key des Empfängers. Richtig
• Wird auf den ServerSocket die methode close() angewandt ( --> servSocket.close() ), dann:
  • Führt dies automatisch bei mit dem ServerSocket verbundenen Sockets zu socket.close();
  • Führt dies automatisch bei mit dem ServerSocket verbundenen Sockets zu einer SocketException
  • ... Die bereits offenen Sockets bleiben offen (Richtig)
• 2 Funktionen (functionA und functionB) sind remotly accessible: In diesem Zusammenhang sind folgende 2 Interfaces implementiert: FunctionAInterface und FunctionBInterface. Ist es sinnvoll, dass die Methodendeklaration von functionA folgendermaßen ausschaut? functionA(FunctionBInterface fBi)
  • Ja, es ist sinnvoll.
  • Nein, es ist nicht sinnvoll.
    • Mein Tipp: An Callback Funktionen denken, ich vermute, dann ist so eine Methodendeklaration sinnvoll.

• Wieviel Sockets und Streams braucht man, um eine bidirektionale Verbindung zu machen (glaube explizit TCP) 2 Sockets, 4 Streams
• Welche sind zulässige Ansätze, um beim Iterieren über eine synchronisierte Datenstruktur threadsafe zu sein.

24.01.2012

• ein prozess kann mehrere threads haben, aber immer mindestens einen - Richtig
• socket implementierungen können in unterschiedlichen programmiersprachen erfolgen - Richtig
• rmi implementierungen können in unterschiedlichen programmiersprachen erfolgen - Falsch (bei der frage bin ich mir nicht sicher, darüber wurde viel diskutiert)
• corba implementierungen können in unterschiedlichen programmiersprachen erfolgen - Richtig
• udp bietet eine sichere datenübertragung - Falsch
• socket ist punkt zu punkt - Richtig
• thread kann runnable implementiert werden - Richtig
• Symmetrische Verschlüsselung nutzt PKI - Falsch
• Lokale Objekte werden serialisiert und Referenzobjekte per Stubs übergeben - Richtig
• Ein Stub ist ein lokales Objekt was die Verbindung zum RemoteObject oder so darstellt - Richtig
• Einen eigens ausgeführten Programmteil krieg ich wenn ich von Thread ableite - Richtig
• RMI kümmert sich um synchronisierung - Falsch
• Ist RMI per se Threadsafe ist. - Falsch
• Kann man java.bla.Thread extenden um als Thread zu agieren? - Richtig
• Verwendet man bei einem asymmetrischen Kryptosystem Public- und Privatekey? - Richtig
• Verwendet man Challange Response zum authentifizieren von Kommunikationspartnern? - Richtig
• TCP ist bidirektional --> ja

20.01.2011

• RMI Port nummer -> 1099
• RSA n x q natürliche zahlen verwendet
• ob sleep n try/catch braucht - ja wegen interruptex.
• ob rsa hybrid ist -> Falsch, verwendet nur asynchrone Verschlüsselung
• rsa Schlüssel mit 2 natürlichen Zahlen
• Bei der RSA-Frage stand afair auch noch dabei, dass n = p * q dann als symmetrischer Schlüssel verwendet wird, was imo falsch ist.

20.01.2010

• UDP ist verbindsicher => FALSCH
• socket ist punkt zu punkt => RICHTIG
• thread kann runnable implementiert werden => RICHTIG