Criptografia com PyCrypto (linux)

cripto.py

"""Modulo para Criptografar Arquivo."""
# -*- coding:utf-8 -*-

import base64
import zlib
from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP


def gerar_chaves(bits=2048):
    """GenerateRSA.

    Generate an RSA keypair with an exponent of 65537 in PEM format
    param: bits The key length in bits
    Return private key and public key
    """
    new_key = RSA.generate(bits, e=65537)
    public_key = new_key.publickey().exportKey("PEM")
    private_key = new_key.exportKey("PEM")
    return private_key, public_key


def criptografar(plaintext, public_key):
    """Função que criptografa usando uma chave pública."""
    # chunk_size = 256 # Exemplo antigo
    chunk_size = 214
    print('Comprimindo: %d bytes' % (len(plaintext)))
    plaintext = zlib.compress(plaintext)
    print('Criptografando %d bytes' % (len(plaintext)))
    rsakey = RSA.importKey(public_key)
    rsakey = PKCS1_OAEP.new(rsakey)

    encrypted = b""
    offset = 0

    while offset < len(plaintext):
        chunk = plaintext[offset:offset+chunk_size]
        if len(chunk) % chunk_size != 0:
            chunk += b" " * (chunk_size - len(chunk))
        encrypted += rsakey.encrypt(chunk)
        offset += chunk_size

    encrypted = base64.b64encode(encrypted)

    print('Base64 criptografado: %d' % len(encrypted))
    return encrypted


def descriptografar(cripto_text, private):
    """Método para Descriptografar."""
    rsakey = RSA.importKey(private)
    rsakey = PKCS1_OAEP.new(rsakey)

    chunk_size = 256
    offset = 0
    descripto = b''
    encrytado = base64.b64decode(cripto_text)

    while offset < len(encrytado):
        descripto += rsakey.decrypt(encrytado[offset:offset+chunk_size])
        offset += chunk_size

    # agora descompactar as paradas
    plaintext = zlib.decompress(descripto)
    return plaintext


if __name__ == '__main__':
    # Chaves
    privada, publica = gerar_chaves()
    # arquivo = b'Exemplo dois'
    # arquivo = 'Horácio Dias'.encode('utf-8')
    caminho = input('digite o caminho do arquivo:')
    with open(caminho, 'rb') as f:
        arquivo = f.read()
        arquivo_criptografado = criptografar(arquivo, publica)
        print(arquivo_criptografado)
        print(descriptografar(arquivo_criptografado, privada))