RSA Private / Public key pair with openssl & Python

rsa_openssl_for_python.md

RSA Private / Pubic key pair

To generate a private / public RSA key pair, you can either use openssl, like so:

$ openssl genrsa -out private.pem 4096  
$ openssl rsa -in private.pem -outform PEM -pubout -out public.pem  

Or, you can use the following python script:

from cryptography.hazmat.backends import default_backend  
from cryptography.hazmat.primitives import serialization  
from cryptography.hazmat.primitives.asymmetric import rsa  
  
  
# save file helper  
def save_file(filename, content):  
   f = open(filename, "wb")  
   f.write(content) f.close()  
  
  
# generate private key & write to disk  
private_key = rsa.generate_private_key(  
    public_exponent=65537,  
    key_size=4096,  
    backend=default_backend()  
)  
pem = private_key.private_bytes(  
    encoding=serialization.Encoding.PEM,  
    format=serialization.PrivateFormat.PKCS8,  
    encryption_algorithm=serialization.NoEncryption()  
)  
save_file("private.pem", pem)  
  
# generate public key  
public_key = private_key.public_key()  
pem = public_key.public_bytes(  
    encoding=serialization.Encoding.PEM,  
    format=serialization.PublicFormat.SubjectPublicKeyInfo  
)  
save_file("public.pem", pem)