def decrypt_str(self, content, key, salt):
# content contains the gcm tag and salt_explicit in plaintext
salt_explicit, gcm_tag = struct.unpack_from('!q16s', content)
cipher = Cipher(algorithms.AES(key),
modes.GCM(initialization_vector=self._bulid_iv(salt, salt_explicit), tag=gcm_tag),
backend=default_backend()
).decryptor()
return cipher.update(content[24:]) + cipher.finalize()
def encrypt_str(self, content, key, salt, salt_explicit):
# return the encrypted content prepended with the
# gcm tag and salt_explicit
cipher = Cipher(algorithms.AES(key),
modes.GCM(initialization_vector=self._bulid_iv(salt, salt_explicit)),
backend=default_backend()
).encryptor()
ciphertext = cipher.update(content) + cipher.finalize()
return struct.pack('!q16s', salt_explicit, cipher.tag) + ciphertext
def generate_session_keys(self, shared_secret):
hkdf = HKDFExpand(algorithm=hashes.SHA256(), backend=default_backend(), length=40, info="key_generation")
key = hkdf.derive(shared_secret)
kf = key[:16]
kb = key[16:32]
sf = key[32:36]
sb = key[36:40]
return [kf, kb, sf, sb, 1, 1]
def decrypt_str(self, content, key, salt):
# content contains the gcm tag and salt_explicit in plaintext
salt_explicit, gcm_tag = struct.unpack_from('!q16s', content)
cipher = Cipher(algorithms.AES(key),
modes.GCM(initialization_vector=self._bulid_iv(
salt, salt_explicit),
tag=gcm_tag),
backend=default_backend()).decryptor()
return cipher.update(content[24:]) + cipher.finalize()
def encrypt_str(self, content, key, salt, salt_explicit):
# return the encrypted content prepended with the
# gcm tag and salt_explicit
cipher = Cipher(algorithms.AES(key),
modes.GCM(initialization_vector=self._bulid_iv(salt, salt_explicit)),
backend=default_backend()
).encryptor()
ciphertext = cipher.update(content) + cipher.finalize()
return struct.pack('!q16s', salt_explicit, cipher.tag) + ciphertext
def generate_session_keys(self, shared_secret):
hkdf = HKDFExpand(algorithm=hashes.SHA256(), backend=default_backend(), length=40, info="key_generation")
key = hkdf.derive(shared_secret)
kf = key[:16]
kb = key[16:32]
sf = key[32:36]
sb = key[36:40]
return [kf, kb, sf, sb, 1, 1]