A Cloud Storage System

A cloud storage system that allows a user (through her client application) to store data on a remote server such that confidentiality of the data stored on the server is guaranteed even if the server is untrusted: data stored on the server is encrypted using a symmetric key known only to the client.

More specifically, data is stored (encrypted with the symmetric key of a user) on the server along with a label and a counter (a version number). When data is to be stored under some label, a new (higher) counter is chosen and the data is stored under the label and the new counter; old data is still preserved (under smaller counters). Different users can have data repositories on one server. These repositories are strictly separated. The system can be used to securely store any kind of data. A user may use our cloud storage system, for example, to store her passwords remotely on a server such that she has access to them on different devices.

Communication between a client and a server is secured and authenticated using functionalities for public-key encryption and digital signatures. Moreover, the functionality for nonce generation is essential to prevent replay attacks (when the client and the server run a sub-protocol to synchronize counter values for labels).

Dependencies

• Java JDK (tested with both openjdk-7 and oraclejdk-8)
• Java Cryptography Extension (only needed for oraclejdk)
• Bouncy Castle Cryptographic API (tested with bcprov-jdk15on-147.jar)
• JavaParser (tested with javaparser-1.0.8.jar)
• SQLJet (tested with sqljet-1.1.10.jar)
• SQLilte (tested with sqlite-jdbc-3.21.0.jar)
• JUnit (tested with junit-4.8.2.jar)
• Apache Ant (tested with ant-1.8.4.jar)
• Beans Binding (tested with beansbinding-1.2.1.jar)
• Miglayout Swing (tested with miglayout-swing-5.0.jar)

Usage

From a Linux + GNOME environment,

./run

downloads the libraries, compiles the classes, and run all the apps (including the GUI). The user ID of the only registered user is 101.

make clean

to delete the local files in the temp directory and the binary files.

Example

Run the following commands from the bin-folder of the compiled project:

java -cp ".:../lib/*" funct.pki.PKIServerApp

java -cp ".:../lib/*" cloudStorage.app.ServerRegisterApp
java -cp ".:../lib/*" cloudStorage.app.ServerApp

java -cp ".:../lib/*" cloudStorage.app.UserRegisterApp 101

java -cp ".:../lib/*" cloudStorage.app.ClientStoreApp 101 pwd PasswordIwantToStore
java -cp ".:../lib/*" cloudStorage.app.ClientRetrieveApp 101 pwd

java -cp ".:../lib/*" cloudStorage.app.UserGUI

java -cp ".:../lib/*" cloudStorage.app.DeleteLocalFiles

Runnable classes

1. Run class funct.pki.PKIServerApp

   To start the public key infrastructure which is needed for registration and lookup of public and verification keys. The PKIServer stores the registered keys at %TEMP%PKI_server.db (to delete registered keys, you will have to delete this file).

2. Run class cloudStorage.app.ServerRegisterApp

   The server registration process. Server registers its keys at the Public-Key Infrastructure and stores the serialized keys in the folder %TEMP%/CloudStorage/server.info

3. Run class cloudStorage.app.ServerApp

   The server app processing the client requests (store, retrieve or provide last counter).

4. Run class cloudStorage.app.UserRegisterApp <user_id [int]>

   This client registration process for the user with that <user_id>. It registers her keys at the Public-Key Infrastucture and stores the serialized keys in the folder %TEMP%/CloudStorage/user$(user_id).info

5. Run class cloudStorage.app.ClientStoreApp <user_id [int]> <label [String]> <msg [String]>

   To allow a user to store a message on the server under a specific label.

6. Run class cloudStorage.app.ClientRetrieveApp <user_id [int]> <label [String]>

   To allow an user to retrieve the message stored on the server under the specific label, by command line interface.

7. Run class cloudStorage.app.UserGUI

   The client user interface which allows an user to store and retrieve message from the server.

8. Run class cloudStorage.app.DeleteLocalFiles

   To delete the local files created which are stored in the folder %TEMP%/CloudStorage and %TEMP%/PKIServer.db