File Encryptor is a program that converts a file into an unreadable and incomprehensible file by using symmetric encryption, so that the secret in the file is undoubtedly cryptic and only the user with the key is able to decrypt and access the content of the file. This program operates on the Command Line Interface (CLI), and you can review the commands provided under Program Usage.
- Fork the repository at https://github.com/somanithpreap/file-encryptor
- Clone the repo
git clone https://github.com/<github_username>/file-encryptor
- Make sure you have a C/C++ compiler and a code editor of your preference installed on your local machine. Check out https://www.mingw-w64.org/downloads/ for downloading compiler and header files. Compile the project using the following commands:
make- compiles both the main program and the test programs
make build- compiles the main program
make test- compiles the test programs
make clean-t- delete the test programs
make clean- delete all binary files
bin/file-encryptor -k <key> -e/-d [-r] <file_1/folder_1> <file_2/folder_2> ... <file_n/folder_n>
-k, --key Specify the key for the encryption and decryption process
-e, --encrypt Set the program to encrypt files
-d, --decrypt Set the program to decrypt files
-r, --recurse Process all file(s) and subfolder(s) in the specified folder(s)
-h, --help Display this help menu
- File structure
/
|
+--- bin/
| [compiled binaries are stored here]
|
+--- src/
| |
| +--- aes.cpp
| +--- aes.h
| +--- file-handler.cpp
| +--- file-handler.h
| +--- main.cpp
| +--- utils.cpp
| +--- utils.h
|
+--- test/
| |
| +--- s-test.cpp
| +--- m-test.cpp
|
+--- LICENSE
+--- Makefile
+--- README.md
- File Handler
bool is_program_file(fs::path path);This is a utility function used in the file handling process to avoid processing the program itself.
void scan_directory(fs::path dir_path, vector<fs::path> &files, bool recurse);Used for scanning a directory and adding it to a path vector.
void process_file(const fs::path &file_path, char op_type, uint8 k_len, uint8 *key);Perform the specified operation (encryption/decryption) on the file specified using the AES. This process will create a temporary file to store the processed data, and replace the original file.
3. The State
class State {
private:
uint8 state[4][4];
public:
State();
State(uint8 in[16]);
void update(uint8 in[16]);
uint8 get_byte(uint8 row_i, uint8 col_i);
void get_word(uint8 index, uint8 holder[4]);
void get_state(uint8 holder[4][4]);
void set_byte(uint8 row_i, uint8 col_i, uint8 value);
void serialize(uint8 holder[16]);
void print();
void add_round_key(uint8 (*round_keys)[4], uint8 round);
void sub_bytes(bool inverse);
void shift_rows(bool inverse);
void mix_columns(bool inverse);
~State(){};
};This class is responsible for taking the bytes imported by file-handler and arranging them into a 4 * 4 array of bytes called "State." Creating "state" is evolved by various methods, as shown in the code snippet. For more information, check aes.cpp to see the usage of each function.
- Key Expansion Algorithm
void key_expansion(uint8 k_len, uint8 *key, uint8 (*holder)[4]);This function takes the format length of the key, which could be either 16, 24, or 32 bytes, the actual key for encryption or decryption, and a holder array to store the round keys. It's resulting in more unique keys (the number of keys is based on the length of the key, which could be either 11 round keys, 13 round keys, or 15 round keys). The holder variable should be uint8 round_keys[28 + k_len][4];. For more information, check the comments in aes.cpp.
- AES Algorithm
class AES {
private:
uint8 rounds;
State state;
public:
AES(uint8 k_len);
void encrypt(uint8 data[16], uint8 holder[16],
uint8 (*round_key)[4]);
void decrypt(uint8 data[16], uint8 holder[16],
uint8 (*round_key)[4]);
~AES(){};
};This class is responsible for the implementation of the AES algorithm, both for encryption and decryption. It uses the data from the state and round keys from round_key and applies methods to the data and key. After all the processing, it is stored in "holder," which is a holder variable for the encrypted (when the "encrypt" function is used) or the decrypted (when the "decrypt" function is used) data. For more information, check aes.cpp.
-
src/main.cpp
This program uses CLI (Command Line Interface) for interaction between the user and the machine. We admit that it is not user-friendly, but It Has To Be This Way due to time constraints. For command line and usage, checkout Program Usage. -
Constant Variables in src/aes.h
They are constant values written to be used in the methods to which they belong. Listen, THEY MUST NOT BE TAMPERED BY ANYONE! in order to make the program run as it should. - SBOX and InvSBOX (Substitution Box and Inverse Substitution Box) are used in the sub_byte() function.
- MIXCOL_MATRIX and InvMIXCOL_MATRIX are used in the mix_columns() function.
- Rcon (Round Constant) is used in the key_expansion() function. -
src/utils.cpp
The functions here are utilities for developers to manipulate bytes, check for errors, etc.
- ERROR() function is for displaying an error message and ending the program if it is not running as expected.
- CHECK_NULL_PTR() function is for checking if a pointer given is a NULL pointer. If it does, it displays an error message.
- display_buffer() function is for displaying a 16-byte buffer.
- l_rotate_word() function is for shifting bytes to the left based on the input. It takes a 4-byte array and a number to determine how far you want to shift a byte.
- r_rotate_word() function is for shifting bytes to the right based on the input. It takes a 4-byte array and a number to determine how far you want to shift a byte.
The program consists of three main parts:
+--------------------------------------+
| +------------------+ |
| | CLI Handler | |
| +------------------+ |
| | |
| V |
| +--------------------+ |
| +~~~~~>| File Handler API |~~~~~~+ |
| | +--------------------+ | |
| | | |
| | +----------------------------+ | |
| +~~| Encryption Algorithm API |<~+ |
| +----------------------------+ |
+--------------------------------------+
- Fork the Project
- Create your Feature Branch
git checkout -b feature/AmazingFeature
- Commit your Changes
git commit -m 'Add some AmazingFeature'
- Push to the Branch
git push origin feature/AmazingFeature
- Open a Pull Request
Distributed under the MIT License. See LICENSE for more information.
somanithpreap - [email protected]
SoksophalSORN - [email protected]
menghorngkao - [email protected]
Project Link: https://github.com/somanithpreap/file-encryptor
-
Contributors
=> Project Manager: https://github.com/somanithpreap
=> Contributor : https://github.com/menghorngkao
=> Contributor : https://github.com/SoksophalSORN -
C/C++ Programming Language
This project utilizes C/C++ for its core functionality. Special thanks to the C and C++ communities for their robust programming languages and support. -
National Institute of Standards and Technologies
National Institute of Standards and Technology (2001) Advanced Encryption Standard (AES). (Department of Commerce, Washington, D.C.), Federal Information Processing Standards Publication (FIPS) NIST FIPS 197-upd1, updated May 9, 2023. https://doi.org/10.6028/NIST.FIPS.197-upd