CPT 341 Cryptography Principles Project

CPT 341 Cryptography Principles Project

Windows Form Application – Symmetric Key Encryption

Topics:

Simple Encryption/Decryption, String Manipulation & Conversion, File I/O, Sequential Text File, ComboBox Control, OpenFileDialog() Control, ASCII Character Set, Asc(), Chr(), SubString(), Mod Operator

Develop a Visual Basic Windows Forms application that will ‘encrypt’ (character shift) the characters in a string based on a symmetric key (process known as symmetric-key cryptography). The application must also ‘decrypt’ the message based on the symmetric key used.

Sample Windows Form Controls

General Requirements

• The clear-text message (that will be ‘encrypted’) is to be stored in a text-file.
  • The text-file is to be selected using an OpenFileDialog runtime control object
  • Text-file contents are to be displayed in a Textbox control located on the Windows form (you can also use this textbox to input clear-text characters)
• Keys are contained in a ComboBox control object. Users can select a particular key resulting in alternate cipher-text output
  • Keys are to be a minimum of 4 digits. Each key digit is used for encoding where your program will move to the next digit for every character in the clear-text message.
    • Since there are a limited number of digits in a key, your program must ‘wrap-back’ to the first digit
  • The selected key must be stored in an array
• Using the same key for encryption, decrypt the cipher-text message and display it in a textbox on the Windows Form
• Since only printable characters are used (see table), if the ANSI code becomes larger than 126, you will need to wrap around to the ANSI code 32 (space)
• Use exception handling where needed.
• Add comments throughout your code

Example: Using a sample key of 58912, the output would be as follows:

Clear Character	N	J	I	T		V	B	N	e	T
ASCII Code	78	74	73	84	32	86	66	78	101	84
ASCII Code + Key Value	83	82	82	85	34	91	74	87	102	86
Shifted Character	S	R	R	U	“	[	J	W	f	V

Clear-Text: “NJIT VBNet”

Cipher-Text: “SRRU”[JWfV”

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