Architecture Plan
Android Text Encryption
Tommy Fritz
Nghia Nguyen
Paul Scott
Sara Wells
Introduction
Encryption as an art has existed for centuries, vastly pre-dating the technological adaptations we take for
granted today. Early encryptions were effective, but generally simple and limited by the time required to
manually encrypt, send, and decrypt messages. In today’s society, almost instantaneous encryptions
performed by computers are part of everyday life and make secure shopping, banking, data exchange, and
other activities possible. One popular form of communication, however, generally lacks any sort of
sophisticated encryption – text messages. Many people send delicate information and conduct private
conversations via text with little protection from third parties who might intercept the message or the
storage of their information in phone company records. In order to fill this void and offer customers a
more securely private means of textual communication, Fish Eating Penguin hopes to develop Text
Encryption, an application for Android phones.
Text Encryption will be a third-party application capable of running on any Android system. It will allow
users to send and receive encrypted text messages using the standard SMS text messaging system, and
will only send encrypted data over that system. Without the Text Encryption program and an appropriate
key/password, any intercepted or stored messages will appear unreadable. In this way, we hope to
provide a safe and secure means of transferring private messages between any two Android phones.
This paper details the specification of the Text Encryption system in two main parts: a requirements
section and a use case section. The requirements section lists all currently anticipated functional and nonfunctional requirements. The use case modeling section provides a use case diagram representing the
system and brief and detailed descriptions of each use case. Additionally, the responsibilities of each
team member are addressed.
System Architecture
Class Diagrams
Sequence Diagram
GUI Sketches
Fish Eating Penguin
Tentative Schedule from Nov. 1st to December 6th
Week 1 – Nov 1st to Nov 7th
Architecture, design, and iterative development plan. We are going to finalize a
schedule and confirm the iterative development plan which includes the system
architecture, class diagrams, sequence diagrams, and use cases.
Week 2 – 8th to 14th
This week we put together the GUI and the basic texting functionality. We want to
be able to read texts and have them show up in the appropriate fields, as well as
write texts and such.
Week 3 – 15th to 21
Put together the encryption interfaces and set it up to encrypt but not send, as well
as decrypt but not receive. Make it so we can see encrypted messages and we have
the ability to decrypt them.
Week 4 – 22nd to 28th
Start plugging in the SMS functionality and make it so that texts are able to be sent
over the SMS system, as well as received, and that it functions as SMS texting
system.
Week 5 – 29th to 5th
Validate that it works and tie loose ends, make it prettier, validate functionality by
testing it on real phones and making sure it meets specifications and expectations.
NEEDS
Texting interface GUI
View texts sent/received/from whom
Text entering screen
Encryption interface
Lots of buttons
Texting functionality
Text Storage
Text sending/receiving
Text writing
Encryption/Decryption System
Algorithm
Import message
Encrypt message/decrypt message
Show message to user encrypted and unencrypted
USE CASE
TEXT MESSAGE ENCRYPTION
Description
Actor
Software user (Sender and Receiver)
Precondition
The software interact with the android text message, showing the ENCRYPT and
DECRYPT icon on the top right of the text message window. User must have android
phone and the text message that supports this software.
Postcondition The input should not over 180 characters. English as default languages, using the roman
alphabets.
Functions



Setup default encrypt key and decrypt key
o To save time, the software automatically use default key to encrypt or
decrypt the given message.
Encrypt text with given key
o Sender is asked to input the key, which is used to encrypt the message.
Decrypt text with given key
o Receiver is asked to input the key, which is used to Decrypt the

Note
message.
Install/Uninstall
o Setup or remove the software from the android phone.
If the receiver input a wrong key code, the software still produce the output, however
the output is not correct as the sender’s intention.
Team Member Contributions
Tommy Fritz – Copy and Paster/Class Diagrams, schedule
Paul Scott- System Architecture and Sequence Diagram
Sara Wells- Interface Sketches and intro/cover page
Nghia Nguyen- Use Case Description and Incremental model
References:
http://developer.android.com/reference/android/telephony/SmsManager.html