/EnigmaPhp

Primary LanguagePHP

Enigma

Story

Hackerman, we need your help. We intercepted correspondence between "the bad guys". We need an app able to both decrypt and encrypt files using ROT13 cipher, Morse code and Rail-fence cipher.

What are you going to learn?

You'll have to:

  • OOP in PHP
  • how to think in algorithms,
  • handle edge cases and exceptions,
  • read from files,
  • use multidimensional arrays.

Tasks

  1. In Enigma we use ArgsParser class to encapsulate passed parameters. Finish implementation of ArgsParser.

    • Data is extracted from the given string array
    • Fields in ArgsParser are NULL if no value was provided

  2. Implement the CipherFactory class with a factory method that provides Cipher implementations. It must work for all ciphers (ROT13, Rail-fence and Morse code).

    • Method isCipherAvailable() returns true if passed name of a supported cipher, false otherwise
    • Method getCipherForArgs() returns proper Cipher instance. If not possible, or invalid key for specific cipher was provided, EnigmaException is thrown

  3. Implement execution engine in Enigma that interprets and executes meaningful commands and displays messages for all cases

    • App prints help menu when passed no arguments, or when the first one is '-h'
    • Providing mode different than '-h', '-e', or '-d' leads to EnigmaException
    • Providing too few arguments leads to EnigmaException. Notice that using '-h' doesn't need any further arguments
    • Providing a not supported cipher name leads to EnigmaException
    • Providing non-existent file path leads to EnigmaException
    • All EnigmaExceptions are caught and their messages are printed to the standard output
    • Method handleCipherOperation() encrypts/decrypts file content using the cipher provided by CipherFactory, and prints the result

  4. Implement ROT13 cipher encrypt and decrypt methods. Upper case letters should appear AFTER lower case ones (see examples below). Create functions encryptLetter(char) and decryptLetter(char) that will do the mapping of single characters. Methods encrypt(String) and decrypt(String) will map entire texts. Examples:

encryptLetter('a') -> 'n'
encryptLetter('l') -> 'y'
encryptLetter('m') -> 'z'
encryptLetter('n') -> 'A'
encryptLetter('o') -> 'B'
decryptLetter('C') -> 'p'
decryptLetter('D') -> 'q'
- All alphabetic characters are encrypted
- All alphabetic characters are decrypted
- Non-alphabetic characters are unchanged
  1. Implement Morse code encryption and decryption. Implementation must support 26 English letters A through Z and Arabic numerals 0 to 9. Convert spaces into word separators ('/'). Every other symbol has to be omitted.
encode("Hello, World!") -> ".... . .-.. .-.. --- / .-- --- .-. .-.. -.."
decode(".... . .-.. .-.. --- / .-- --- .-. .-.. -..") -> "HELLO WORLD"
- Message gets encrypted into Morse code using word separators
- Non-alphanumeric characters are omitted from the encrypted message
- Message gets decrypted using uppercase letters
  1. Implement Rail-fence cipher encryption and decryption. Encrypted message should contain all non alphanumeric characters, letters must stay the same (don't change the case)
encrypt("Hello World!") -> "Horel ol!lWd" // key = 3
decrypt("Horel ol!lWd") -> "Hello World!"
- Message gets encrypted
- Letter cases are unchanged
- Message gets decrypted

General requirements

None

Background materials