Implementing-cryptography-using-python

Chapter 2 ■ Cryptographic Protocols and Perfect Secrecy 45
critical=False,
# Sign the CSR with our private key.
).sign(key, hashes.SHA256(), default_backend())
with open("csr.pem", "wb") as f:
f.write(csr.public_bytes(serialization.Encoding.PEM))
You can use the openssl command to view the CSR, as shown here:
$ openssl req -text -in csr.pem
Certificate Request: Data: Version: 0 (0x0) Subject: C=US, ST=CA,
L=San Francisco, O=Python Cryptography, CN=8gwifi.org Subject Public
Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (2048
bit) Modulus (2048 bit): Encrypted RSA key generated with the code
$ cat /tmp/rsakey.pem -----BEGIN RSA PRIVATE KEY----- Proc-Type:
4,ENCRYPTED DEK-Info: AES-256-CBC,EA2EB61CCC7A2FFD9D83D9D103B74F69
nuslMfQNj17cAdwCKWtWhcXCtOqpk6ii0SmxcuUgJWg5iUujN4p6LYHbWkalUTvi
...... -----END RSA PRIVATE KEY----- Generated CSR in the PEM
format $ cat /tmp/csr.pem -----BEGIN CERTIFICATE REQUEST-----
MIIC0jCCAboCAQAwZTELMAkGA1UEBhMCVVMxCzAJBgNVBAgMAkNBMRYwFAYDVQQH
DA1TYW4gRnJhbmNpc2NvMRwwGgYDVQQKDBNQeXRob24gQ3J5cHRvZ3JhcGh5MRMw
EQYDVQQDDAo4Z3dpZmkub3JnMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKC
..................... -----END CERTIFICATE REQUEST-----
Generating a Self-Signed Certificate
In cryptography and computer security, a self-signed certificate is an identity
certificate that is signed by the same entity whose identity it certifies.
Examine the following Python code. In the example, you will create a selfsigned
certificate named certificate.pem. When generating the self-signed
certificates, the issuer and the signer are the same:
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography import x509
from cryptography.x509.oid import NameOID
from cryptography.hazmat.primitives import hashes
import datetime
# Generate Key (RSA,DSA,EC)
encryptedpass = b"Ilik32Cod3"
key = rsa.generate_private_key( public_exponent=65537, key_size=2048,
backend=default_backend() )