Pseudo-Random Encryption

This script provides Python functions for symmetric encryption and decryption using pseudo-random number generation.

By default, the script takes in a message to encrypt and prints 2 lines of python code to stdout, which when executed will give back the original message. e.g. python main.py ishaan outputs the following

from random import randrange, seed; seed('5822100138856949'); m = 'b\x04v\x1b\x16\x05\x03\x00a\x00\x0e@4P'
print(''.join((chr(randrange(128)^ord(c))for c in m if not randrange(2))),end='')

The script also offers modularity, allowing each function to be used independently as needed.

The key in this encryption system is a tuple of 3 values: seed, size_multiplier and char_range. They are interpreted as:

• seed: main seed value for encryption, passed to python's random library as is.
• size_multiplier: size multiplier for encrypted message. i.e. $\frac{\text{length of encrypted message}}{\text{length of original message}} \approx \text{size multiplier}$
• char_range: unicode character range for each char of encrypted message. Does not impose any limitation on character range of original message.

Usage

Try: python main.py -h for help message and usage instructions.

usage: Pseudo-Random Encryptor [-h] [--hex] [--file] [--decrypt] [--values-only] [--seed SEED] [--size SIZE] [--char-range CHAR_RANGE]
                               [--output OUTPUT] [--garbage GARBAGE]
                               arg
positional arguments:
arg                   The text to be encrypted, or the path of the file if -f flag is set.
options:
-h, --help            show this help message and exit
--hex, -x             [default:False] Indicates that the encrypted message is to be hex encoded. (or the message is to be decoded from
hex, if -d is set)
--file, -f            [default:False] Indicate that the given argument is a file path insead of string.
--decrypt, -d         [default:False] Indicate that the message is to be decrypted, not encrypted.
--values-only, -vo    [default:False] Give key values and encrypted message only, not the entire code (Ignored if -d flag is set).
--seed SEED, -s SEED  [default:random] The seed for encrypting/decrypting. Passed to random library as seed.
--size SIZE, -z SIZE  [default:2] Approximately equal to len(encrypted) / len(original).
--char-range CHAR_RANGE, -r CHAR_RANGE
[default:128] Unicode character range of the encrypted message (Does not limit the original message).
--output OUTPUT, -o OUTPUT
[default:stdout] Specify a text file where the output code/values will be saved.
--garbage GARBAGE, -g GARBAGE
[default:random] Seed for garbage values which randomize encrypted text.

Functionality

Encrypting a Message

The encrypt function takes a message and encrypts it based on specified parameters, including:

• Seed: Main key for encryption, passed to the random library as a seed.
• Size Multiplier: Factor determining the size of the encrypted message.
• Character Range: Unicode character range of the encrypted message.
• Garbage Seed: Seed for randomizing the output.
• Hex Encoding: Indicates whether the output should be hex encoded.

Decrypting an Encrypted Message

The decrypt function decrypts an encrypted message based on given parameters, including:

• Seed: Main key for decryption, passed to the random library as a seed.
• Size Multiplier: Factor determining the size of the original message.
• Character Range: Unicode character range of the encrypted message.

Generating Python Code for Decryption

The give_code function generates Python code to decrypt a message based on specified parameters, including:

• Seed: Main key for decryption, passed to the random library as a seed.
• Size Multiplier: Factor determining the size of the original message.
• Character Range: Unicode character range of the encrypted message.
• Hex Encoding: Indicates whether the encrypted message is hex encoded.

Generating Key Values for Decryption

The give_values function generates a formatted string containing encrypted message and key values for decryption, including:

• Seed: Main key for decryption, passed to the random library as a seed.
• Size Multiplier: Factor determining the size of the original message.
• Character Range: Unicode character range of the encrypted message.
• Hex Encoding: Indicates whether the output message is hex encoded.

Input Handling

The get_input function sets up an argument parser and returns parsed arguments in dictionary form.

Main Functionality

The run function serves as the main entry point, handling the encryption, decryption, and output functionalities based on user inputs and parameters.

Examples

1. With no flags

$ python main.py message

from random import randrange, seed; seed('13234983975254888'); m = '2LA2\x01D\x1e\x0eQ8y\x1eB\x1d+r>\x16'
print(''.join((chr(randrange(128)^ord(c))for c in m if not randrange(2))),end='')

2. Get only the encoded message and key values

$ python main.py message --values-only

message:        "\x17\rk#\\/\r\x1b\x01$)\x1fC='("
seed:           '5008982697256702'
size seed:      2
char range:     128
hex encoded:    False

3. Write to an output file

$ python main.py "secret message" -o output.py
$ python output.py

secret message

4. Read from file

$ python main.py -f input.txt -o output.py
$ python output.py > decoded.txt
$ diff decoded.txt input.txt

# no diff

5. Specify a size multiplier

$ python main.py "secret" --seed 0 --size 5 -vo -g 0

message:        'U2N5|^0\x0e>\x1cO\x03\x1cjM@\x1d|ddf+\\'
seed:           '0'
size seed:      5
char range:     128
hex encoded:    False

$ python main.py "secret" --seed 0 --size 1 -vo -g 0

message:        'g9su\x057'
seed:           '0'
size seed:      1
char range:     128
hex encoded:    False

6. Specifying garbage seed

$ python main.py "secret" --seed 0 -vo -g 0

message:        '-2$ud\x12&\x1a'
seed:           '0'
size seed:      2
char range:     128
hex encoded:    False

$ python main.py "secret" --seed 0 -vo -g 1

message:        '\x1e2Bud\x12&\x1a'
seed:           '0'
size seed:      2
char range:     128
hex encoded:    False

7. Decrypting an Encrypted Message

message:        '}/xf\x01-'
seed:           '0'
size seed:      1
char range:     128
hex encoded:    False

$ python main.py -d '}/xf\x01-' -s 0 -z 1

ishaan

8. Using hex values

$ python main.py 'ishaan' -vo -s 0 -z 1 -x

message:        '7D2F7866012D'
seed:           '0'
size seed:      1
char range:     128
hex encoded:    True

$ python main.py -d '7D2F7866012D' -vo -s 0 -z 1 -x

ishaan

9. Customizing character range

$ python main.py "secret" --seed 0 --char-range 1024 -vo

message:        'ͱɾϧâ]ͱɿ̃'
seed:           '0'
size seed:      2
char range:     1024
hex encoded:    False

10. Decrypting a file

$ python main.py -d /path/to/file.enc -vo -s 0 -z 1 -o /path/to/file.dec
$ cat /path/to/file.dec

super secret text in file