Sample implementation of client-server signing and verification of large files as described in the python rsa package documentation: https://stuvel.eu/python-rsa-doc/usage.html#how-it-usually-works

large_file_rsa_encryption.py

import rsa
import subprocess

# First, initial client-server communication; key pair generation and exchange on the client side
(pubkey, privkey) = rsa.newkeys(512)

###########  server side
INPUT_FILE = "/home/user/path/file"

server_aes_key = rsa.randnum.read_random_bits(128)
msg = "{i} asset encryption"
err_vals = {}
try:
    cmd = "openssl enc -aes-256-cbc -salt -in {i} -out {i}.enc -k {k}".format(i=INPUT_FILE, k=server_aes_key)
    subprocess.run(cmd, shell=True, check=True)
except subprocess.CalledProcessError as e:
    msg += " error occurred.\nReturn code: {rc}\nStderr output of the process: {stderr}"
    err_vals = {"rc": e.returncode, "stderr": e.stderr if e.stderr is not None else ""}
else:
    msg += " was successful"
    encrypted_aes_key = rsa.encrypt(server_aes_key, pubkey)
finally:
    print(msg.format(i=INPUT_FILE, **err_vals))
# Then serve the encrypted_aes_key and AES-encrypted INPUT_FILE to the client



########### client side
# Retrieve the encrypted_aes_key and AES-encrypted INPUT_FILE
import rsa
import subprocess

client_aes_key = rsa.decrypt(encrypted_aes_key, privkey)
# assert client_aes_key == server_aes_key

msg = "{i} asset decryption"
err_vals = {}
try:
    cmd = "openssl enc -aes-256-cbc -d -salt -in {i}.enc -out {i}.dc -k {k}".format(i=INPUT_FILE, k=client_aes_key)
    subprocess.run(cmd, shell=True, check=True)
except subprocess.CalledProcessError as e:
    msg += " error occurred.\nReturn code: {rc}\nStderr output of the process: {stderr}"
    err_vals = {"rc": e.returncode, "stderr": e.stderr if e.stderr is not None else ""}
else:
    msg += " was successful"
finally:
    print(msg.format(i=INPUT_FILE, **err_vals))