import nacl.utils
from nacl.public import PrivateKey, Box

# Generate Bob's private key, which must be kept secret
skbob = PrivateKey.generate()

# Bob's public key can be given to anyone wishing to send
#   Bob an encrypted message
pkbob = skbob.public_key

# Alice does the same and then Alice and Bob exchange public keys
skalice = PrivateKey.generate()
pkalice = skalice.public_key

# Bob wishes to send Alice an encrypted message so Bob must make a Box with
#   his private key and Alice's public key
bob_box = Box(skbob, pkalice)

# This is our message to send, it must be a bytestring as Box will treat it
#   as just a binary blob of data.
input = input("what message would like to send to alice? \n")
message = bytes(input, 'utf-8')
print("encrypting message to:")
# Encrypt our message, it will be exactly 40 bytes longer than the
#   original message as it stores authentication information and the
#   nonce alongside it.
encrypted = bob_box.encrypt(message)

print(encrypted)
# Alice creates a second box with her private key to decrypt the message
alice_box = Box(skalice, pkbob)

# Decrypt our message, an exception will be raised if the encryption was
#   tampered with or there was otherwise an error.
plaintext = alice_box.decrypt(encrypted)
# get rid of bytestring notation and such
print("decrypting message to:")
print((plaintext.decode('utf-8')))