Cryptography report of LIUCrypto

School of Engineering Depar Depar tment tment of Computer Computer and Commu Commu ni cation cation E ngin eer in g  CENG625 –  Cr yptog yptogrr aphy & Advanced Advanced Computer Computer Securi ty  F all 2013-20 2013-2014 14

Supervisor: Dr. Zouhair El-Bazzal

Done by: Ibrahim Wazneh Khadija Zahwe Mohammad Gaith Mohammad Dhainy

January 16, 2014

 Introduction: The

MD5  message-digest

algorithm is a widely used cryptographic hash function producing a

128-bit (16-byte) hash value, typically expressed in text format as a 32 digit hexadecimal number. MD5 has been utilized in a wide variety of cryptographic applications, and is also commonly used to verify data integrity. Thus, we have created our project based on MD5 encryption. The proposed project is centered on a web server connecting two (or more) different clients. Figure 1 shows the main layout of the application consisting of four main buttons: Send , ReadNew, ReadHistory , and Delete all msgs .

 Figure1: Main Layout of the Project 

Use Case: As mentioned before, a web server connects both clients (sender and receiver). The procedure of sending and receiving is illustrated by explaining the functions of the four buttons as follows: “Send” Button: When pressing the “send” button, a new layout is  presented, allowing the user

(where his phone number is already retrieved from the device itself) to enter the destination phone number in the first field (Figure 2), and the message to be encrypted and sent in the other field. Next, the message is encrypted using the MD5 encryption algorithm, using the key = LIUcryptography and initial vector iv = MD5(MD5(iv)).

 Figure 2: Filled Fields to Send a Plaintext

When the “send” button is pressed in the above layout, the message is encrypted as illustrated  before, and then sent as a cipher text where the user is notified as shown in figure 3:

 Figure 3: User Notification of Encrypted Sent Message

Before completing the explanation of the remaining buttons, we would like to clarify the web server characteristics. Our web server consists of a database table saving the features shown in table 1 (example illustrated in figure 4): Table 1: Web Server Features

From

To

Message (Encrypted)

Time

Read

From: contains the phone number of the sender To: contains the phone number of the destination Message: contains the encrypted sent message Time: automated time added by the server itself when a new message is added Read: Boolean column to show whether the message is seen (true) or not seen (false by default)

 Figure 4: Database Web Server

“ReadNew” Button: When pressing the “readNew” button, the client retrieves the new messages

(unread messages) from the web server. Messages are searched based on two fields: To field = client  phone number and Read field = False (message not read). As a result, the messages are shown, as in figure 5, for the client number: 03734475

 Figure 5: New Messages Receieved to Client: 03734475

Then, the user realizes (if pressing the ReadNew button again) that the layout contains no messages (Figure 6). That’s due to the change of flag Seen (Seen field is changed from False after the first press on the button.

 True)

Figure 6: No New Messages for a Second Press

“ReadHistory” Button: After pressing this button, the client retrieves a history of his messages

from the webserver. Such messages are explored based on the field: To = client phone number. Figure 7 shows a simple example of retrieving history of messages for the client who se number: 03734475

 Figure 7: Message's History for Client: 03734475

“ Delete All Msgs “ Button : By pressing this button , all messages that are found in the

ReadHistory table are deleted. Figure 8 shows that all messages that were sent to 96170027249 device are deleted and then return to the main page.

Figure 8: Deleting messages and returning to the main page