Encoder

This is a simple tool that is able to encode plaintext to an obfuscated string, and decode an obfuscated string into plaintext. The cipher matches the specifications laid out in Encoder (New) V1.pdf.

Structure

The main OffsetCipher class implements the Cipher interface, including its interface methods. This is done intentionally for polymorphism and code reusability. It also adheres to the Strategy design pattern.

Logic

• The basis of the cipher is that the given offset is converted into its index notation within the reference table.
• This tool generates Mapper dictionaries for the respective strings based on the given offset.
• Finally, the Mapper(s) are used in conjunction with stringbuilders to encode or decode the given text.

OffsetCipher

• Designed to be modular
  • Allow user to set their own custom reference table (using instanced setReferenceTable())
• Performs logical checks before carrying out processes.
  • i.e whether the first character/offset is a valid offset within the reference table.
• Applies a simple Modulo strategy to wrap around the reference table where necessary.

JUnit Tests

• There are three tests in total.
• Two are designed in emulation of the examples provided in Encoder (New) V1.pdf (namely, using the strings "HELLO WORLD" and the letters B and F, respectively).
• The third test is a robustness test whereby it loops x times, generates a new random string each time, and asserts the correct return value each time.
  • How many times it runs can be adjusted using the testRounds variable in the @BeforeAll setup() method.