bundled-CTR

Getting Started

Implement Environment

Ubuntu 20.04

Prerequisites

We use crypto++ library. You can install the library by following below:

wget https://github.com/weidai11/cryptopp/archive/refs/tags/CRYPTOPP_8_8_0.zip
unzip CRYPTOPP_8_8_0.zip
cd ./cryptopp-CRYPTOPP_8_8_0
make
make test
sudo make install

And you can use the library when you compile your code:

g++ <Your Source Code *.cpp> -Lcryptopp -lcryptopp

Function

Metadata

	vector<byte> metadata_gen(int len)
	vector<byte> metadata_enc(vector<byte> metadata, byte* counter, byte* key, byte* nonce)

For generating metadata, you only need the length of plaintext.

For encrypting metadata, you need metadata generated with metadata_gen function, 8-byte-sized counter value, 16-byte-sized encryption key and 8-byte-sized nonce value. To elaborate, the counter has the most recently used counter value, the key and the nonce are also used when you encrypt main data. When encrypting, you can make initial value with nonce and 8-byte-size array initialized to 0x00.

Encryption/Decryption

	vector<byte> encryption(byte* nonce, byte* counter, string plaintext, byte* key)
	vector<byte> decryption(byte* nonce, vector<byte> bundle, byte* key, vector<byte> metadata)

For encryption data, you need 8-byte-size nonce, 8-byte-size counter, plaintext and 16-byte-sized key. Similarly, nonce, key are used when decrypting ciphertext bundles. One different thing is metadata in encrypted form.

Index Search

	int search_block_index(vector<byte> metadata, int index);
	int search_real_index(vector<byte> metadata, int index);
	int search_counter_block(vector<byte> metadata, int index);

These functions are used when you have the index of plaintext and want to find the index at the ciphertext.

The first input of these functions is metadata wirh decrypted form.

Class

bundled-CTR

	class bundled_CTR
	{
		private:
			vector<byte> main_data;
			vector<byte> meta_data;
			byte key[AES::BLOCKSIZE];
			byte nonce[AES::BLOCKSIZE/2];

		public:

			bundled_CTR(byte* key, byte* nonce);
	
			bundled_CTR(vector<byte> data, vector<byte> meta, byte* key, byte* nonce);

			~bundled_CTR();

			vector<byte> print_data();

			vector<byte> print_meta();

			Modi_info Insertion(string text, int index);

			Modi_info Deletion(int del_len, int index);

			Modi_info Replacement(string text, int index);

			int Fragcheck(vector<int> bundle_list, int range, int num);

			void Defrag();
	};

How to use the class

Download and save crypto.cpp and crypto.h to the folder where you intend to proceed with your project. And add

#include "crypto.h"

in the code file. When you compile your code,

g++ <Your Source Code *.cpp> -lcryptopp

will work.

In your code, you can declare your class like below.

bundled_CTR b(key, nonce);

Also, you can first create your ciphertext with Insertion function.

b.Insert(plaintext, 0);

plaintext is your input data and 0 is the first index.

After that, you can use all modification functions in the class.

b.Insert(text, index);
b.Delete(length, index);
b.Replacement(text, index);

If you want to print your ciphertext, you can use print_data function in the class.

b.print_data();

Test

Users can compile and run test file on your local environment if you install all of the project.

We have two test files: one for comparing execution times based on file sizes and the other for comparing execution times based on the size of data modified at once.

To execute the files, proper text files must be prepared in advance.

Therefore, users need to compile test_file_gen.cpp and execute it first.

When users run the test_file_gen, it creates text files ranging from 10KB to 390KB in 10KB increments with 200KB size text file.

Users must prepare 200KB size text file named 204800.txt with any contents in English.

Each file has "(file size).txt" and the unit of file size is in bytes.

Test1 - Based on file sizes

For Test1, (mode)_test1.cpp files need to be compiled. When running the excutable files, the text files previously created must be in the same folder.

When running the file, users can see the text below:

	What size (KB): 

Then, write the file size in KB.

The excutable file generates a text file which records the execution time of modification function.

Recording file name has the form (mode)_(file size).txt and the unit of file size is in bytes.

Test2 - Based on the size of data modificated at once

For Test2, (mode)_test2.cpp files need to be compiled. In Test2, users only need to put 200KB size file (204800.txt) in the same folder.

When running the file, users can see the text below:

	What size (*10): 

Then, write the modified data size in byte.

The excutable file generates a text file which records the execution time of modification function.

Recording file name has the form (mode)_(file size).txt and the unit of file size is in bytes.