from nacl.encoding import Base64Encoder
from nacl.signing import SigningKey
# Generate a new random signing key
signing_key = SigningKey.generate()
# Sign a message with the signing key
signed_b64 = signing_key.sign(b"Attack at Dawn", encoder=Base64Encoder)
# Obtain the verify key for a given signing key
verify_key = signing_key.verify_key
# Serialize the verify key to send it to a third party
verify_key_b64 = verify_key.encode(encoder=Base64Encoder)

from nacl.encoding import Base64Encoder
from nacl.signing import VerifyKey
# Create a VerifyKey object from a base64 serialized public key
verify_key = VerifyKey(verify_key_b64, encoder=Base64Encoder)
# Check the validity of a message's signature
# The message and the signature can either be passed together, or
# separately if the signature is decoded to raw bytes.
# These are equivalent:
verify_key.verify(signed_b64, encoder=Base64Encoder)
signature_bytes = Base64Encoder.decode(signed_b64.signature)
verify_key.verify(signed_b64.message, signature_bytes,
                  encoder=Base64Encoder)
# Alter the signed message text
forged = signed_b64[:-1] + bytes([int(signed_b64[-1]) ^ 1])
# Will raise nacl.exceptions.BadSignatureError, since the signature check
# is failing
verify_key.verify(forged)

Traceback (most recent call last):
 ...
nacl.exceptions.BadSignatureError: Signature was forged or corrupt