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https://github.com/markqvist/Reticulum.git
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Handle AES-256 compatibility in Identity
This commit is contained in:
Mark Qvist
parent
3cbcbec942
commit
437da99d63
2 changed files with 63 additions and 61 deletions
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@ -37,7 +37,8 @@ from RNS.Cryptography import AES
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from RNS.Cryptography.AES import AES_128_CBC
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from RNS.Cryptography.AES import AES_256_CBC
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# import RNS # TODO: Remove
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# TODO: Remove after migration
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import RNS
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class Token():
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"""
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@ -66,23 +67,11 @@ class Token():
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self._signing_key = key[:16]
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self._encryption_key = key[16:]
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####################################################################
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self.mode_legacy = AES_128_CBC # TODO: Remove after migration
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self._signing_key_128 = key[:16] # TODO: Remove after migration
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self._encryption_key_128 = key[16:] # TODO: Remove after migration
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####################################################################
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elif len(key) == 64:
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self.mode = AES_256_CBC
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self._signing_key = key[:32]
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self._encryption_key = key[32:]
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####################################################################
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self.mode_legacy = AES_128_CBC # TODO: Remove after migration
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self._signing_key_128 = key[:16] # TODO: Remove after migration
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self._encryption_key_128 = key[16:32] # TODO: Remove after migration
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####################################################################
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else: raise ValueError("Token key must be 128 or 256 bits, not "+str(len(key)*8))
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else: raise TypeError(f"Invalid token mode: {mode}")
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@ -93,11 +82,8 @@ class Token():
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else:
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received_hmac = token[-32:]
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expected_hmac = HMAC.new(self._signing_key, token[:-32]).digest()
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expected_hmac_128 = HMAC.new(self._signing_key_128, token[:-32]).digest() # TODO: Remove after migration
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# TODO: Reset after migration
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# if received_hmac == expected_hmac: return True
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if received_hmac == expected_hmac or received_hmac == expected_hmac_128: return True
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if received_hmac == expected_hmac: return True
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else: return False
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@ -105,6 +91,7 @@ class Token():
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if not isinstance(data, bytes): raise TypeError("Token plaintext input must be bytes")
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iv = os.urandom(16)
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# RNS.log(f"Encrypting with {self.mode}") # TODO: Remove
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ciphertext = self.mode.encrypt(
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plaintext = PKCS7.pad(data),
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key = self._encryption_key,
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@ -116,6 +103,7 @@ class Token():
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def decrypt(self, token = None):
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# RNS.log(f"Trying decryption with {self.mode}") # TODO: Remove
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if not isinstance(token, bytes): raise TypeError("Token must be bytes")
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if not self.verify_hmac(token): raise ValueError("Token HMAC was invalid")
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@ -123,30 +111,14 @@ class Token():
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ciphertext = token[16:-32]
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try:
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try:
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# RNS.log(f"Trying decryption with {self.mode}", RNS.LOG_DEBUG) # TODO: Remove
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plaintext = PKCS7.unpad(
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self.mode.decrypt(
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ciphertext = ciphertext,
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key = self._encryption_key,
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iv = iv))
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plaintext = PKCS7.unpad(
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self.mode.decrypt(
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ciphertext = ciphertext,
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key = self._encryption_key,
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iv = iv))
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# RNS.log(f"Decrypted packet with {self.mode}", RNS.LOG_DEBUG) # TODO: Remove
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return plaintext
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# TODO: Remove after migration ############################
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except Exception as e:
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# RNS.log(f"{self.mode} decryption failed", RNS.LOG_DEBUG) # TODO: Remove
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# RNS.log(f"Trying decryption with {self.mode_legacy}", RNS.LOG_DEBUG) # TODO: Remove
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plaintext = PKCS7.unpad(
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self.mode_legacy.decrypt(
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ciphertext = ciphertext,
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key = self._encryption_key_128,
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iv = iv))
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# RNS.log(f"Decrypted packet with {self.mode_legacy}", RNS.LOG_DEBUG) # TODO: Remove
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return plaintext
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###########################################################
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# RNS.log(f"Decrypted packet with {self.mode}") # TODO: Remove
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return plaintext
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except Exception as e:
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RNS.trace_exception(e) # TODO: Remove after migration
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@ -79,13 +79,16 @@ class Identity:
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HASHLENGTH = 256 # In bits
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SIGLENGTH = KEYSIZE # In bits
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NAME_HASH_LENGTH = 80
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TRUNCATED_HASHLENGTH = RNS.Reticulum.TRUNCATED_HASHLENGTH
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NAME_HASH_LENGTH = 80
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TRUNCATED_HASHLENGTH = RNS.Reticulum.TRUNCATED_HASHLENGTH
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"""
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Constant specifying the truncated hash length (in bits) used by Reticulum
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for addressable hashes and other purposes. Non-configurable.
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"""
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DERIVED_KEY_LENGTH = 512//8
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DERIVED_KEY_LENGTH_LEGACY = 256//8
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# Storage
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known_destinations = {}
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known_ratchets = {}
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@ -544,8 +547,6 @@ class Identity:
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RNS.log("The contained exception was: "+str(e))
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def __init__(self,create_keys=True):
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self.derived_key_length = 64
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# Initialize keys to none
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self.prv = None
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self.prv_bytes = None
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@ -678,8 +679,20 @@ class Identity:
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shared_key = ephemeral_key.exchange(target_public_key)
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# TODO: Reset after migration
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# derived_key = RNS.Cryptography.hkdf(
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# length=Identity.DERIVED_KEY_LENGTH,
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# derive_from=shared_key,
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# salt=self.get_salt(),
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# context=self.get_context(),
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# )
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# Use legacy derived key length (AES-128) during migration by
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# default. This allows AES-256 capable instances on RNS 0.9.5
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# to still communicate with older versions. This migration
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# handling will be removed in RNS 0.9.6.
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derived_key = RNS.Cryptography.hkdf(
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length=self.derived_key_length,
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length=Identity.DERIVED_KEY_LENGTH_LEGACY,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context(),
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@ -702,6 +715,37 @@ class Identity:
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:returns: Plaintext as *bytes*, or *None* if decryption fails.
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:raises: *KeyError* if the instance does not hold a private key.
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"""
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# This handles decryption during migration to AES-256 where
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# older instances may still use AES-128. If decryption fails
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# initially, AES-128 will be attempted as a fallback mode.
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# This handler will be removed in RNS 0.9.6.
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def migration_decrypt(shared_key, ciphertext):
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try:
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derived_key = RNS.Cryptography.hkdf(
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length=Identity.DERIVED_KEY_LENGTH,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context())
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token = Token(derived_key)
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plaintext = token.decrypt(ciphertext)
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# TODO: Remove after migration
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# If decryption fails, try legacy decryption mode
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except Exception as e:
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RNS.log("Decryption failed, attempting legacy mode fallback", RNS.LOG_DEBUG)
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derived_key = RNS.Cryptography.hkdf(
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length=Identity.DERIVED_KEY_LENGTH_LEGACY,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context())
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token = Token(derived_key)
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plaintext = token.decrypt(ciphertext)
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return plaintext
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if self.prv != None:
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if len(ciphertext_token) > Identity.KEYSIZE//8//2:
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plaintext = None
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@ -716,15 +760,8 @@ class Identity:
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ratchet_prv = X25519PrivateKey.from_private_bytes(ratchet)
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ratchet_id = Identity._get_ratchet_id(ratchet_prv.public_key().public_bytes())
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shared_key = ratchet_prv.exchange(peer_pub)
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derived_key = RNS.Cryptography.hkdf(
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length=self.derived_key_length,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context(),
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)
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plaintext = migration_decrypt(shared_key, ciphertext)
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token = Token(derived_key)
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plaintext = token.decrypt(ciphertext)
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if ratchet_id_receiver:
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ratchet_id_receiver.latest_ratchet_id = ratchet_id
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@ -741,15 +778,8 @@ class Identity:
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if plaintext == None:
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shared_key = self.prv.exchange(peer_pub)
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derived_key = RNS.Cryptography.hkdf(
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length=self.derived_key_length,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context(),
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)
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plaintext = migration_decrypt(shared_key, ciphertext)
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token = Token(derived_key)
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plaintext = token.decrypt(ciphertext)
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if ratchet_id_receiver:
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ratchet_id_receiver.latest_ratchet_id = None
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