Cryptography

Data Encryption and Decryption Tool

NOMENCLATURE

For ease of use, this tool represents data to be ciphered and encryption keys as sequences of bytes in hexadecimal. Each pair of hexadecimal characters represents a single byte in little-endian order, where the lower byte is on the lower address (left side).

For example, the string 4142434445464748 represents an array of 8 bytes: [65, 66, 67, 68, 69, 70, 71, 72]. A 32-bit integer with the value 1 is represented as: 0100000000, and the hexadecimal number 0x12345678 will be represented as: 78563412.

USAGE

To compile, you need to install boost library:

# Ubuntu
∼/Cryptography> sudo apt-get install libboost-all-dev

# Mac OS
∼/Cryptography> brew install boost

# Windows
∼/Cryptography> choco install boost

Then, follow the command line syntax and options described below:

Terminal Command:

∼/Cryptography> make

To use mypgp, follow the command line syntax and options described below:

Terminal Command:

∼/Cryptography> ./mypgp -h

DESCRIPTION

./mypgp [-xor | -aes | -rsa | -pgp] [-c | -d] [-b] [KEY]

The MESSAGE is read from standard input.

• xor: Perform encryption/decryption using the XOR algorithm.
• aes: Perform encryption/decryption using the AES algorithm.
• rsa: Perform encryption/decryption using the RSA algorithm.
• pgp: Perform encryption/decryption using both the RSA and AES algorithms.
• c: Indicates that the MESSAGE is clear text and should be ciphered.
• d: Indicates that the MESSAGE is ciphered text and should be deciphered.
• b: Block mode. For XOR and AES algorithms, this mode works on one block only. A block is of the same size as the key. It means the message must be of the same length as the key. MESSAGE and KEY must be of the same size.
• g P Q: For RSA only, generate a public and private key pair from the prime numbers P and Q.

Note

All symmetric algorithms must accept the "-b" option for block mode. In block mode, only one block will be treated. A block is of the same size as the key. The message must be of the same length as the key.

Without the "-b" modifier, your algorithm must work in stream mode, meaning the message to cipher/decipher can be of any length.

EXAMPLES

Here are some usage examples of the mypgp tool:

• Encrypt a message using XOR:

  cat message | ./mypgp -xor -c -b 4142434445464748

• Decrypt a message using AES:

  cat message | ./mypgp -aes -d -b 785634121110

• Generate RSA key pair from prime numbers P and Q:

  cat message | ./mypgp -rsa -g P Q

• Encrypt a message using PGP:

  cat message | ./mypgp -pgp -c -b 4142434445464748

Unit Testing

To run the unit tests, follow the command line syntax and options described below:

Terminal Command:

∼/Cryptography> make test

the output should be:

[ XOR ] test 1.0 passed,   ciphered : 1e001e154f53120c000910
[ XOR ] test 1.5 passed, deciphered : 68656c6c6f20776f726c64
...
Tests passed successfully!

[ AES ] test 1.0 passed,   ciphered : 0449b86c61084ddf8f7756e27454acc8
[ AES ] test 1.5 passed, deciphered : c2416f4796f06574
...
Tests passed successfully!

[ RSA ] test 1.0 passed, ciphered:dc0bd7367d04e5a9e9e14467ff38de0625b3cfa5aabbe86def48bfc93e97aab713d70abf83d263a6dd6570c6d297cc44bad2e0dd2cf7b4c3e0a9749d68ca11a8
[ RSA ] test 1.5 passed.
...
Tests passed successfully!

[ PGP ] test 1.0 passed, ciphered:2518577e4c5b43f39200c83d8a388387e65cfad2bca86b6400a6b2ec7797babe819004a1005efa34af011147fd994d2d80239a846cff8672025927674661c1456e9838c0daec43e6e71305cf6cfa6b7b
[ PGP ] test 1.5 passed.
...
Tests passed successfully!

Cleaning up...
Eliminado: test/ciphered
Eliminado: test/deciphered
Eliminado: test/message

Note: Replace the example keys and input data with your actual data when using the tool.