diff --git a/.gitignore b/.gitignore
index 5996501..5bdb4cc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -44,6 +44,7 @@ nosetests.xml
 coverage.xml
 *,cover
 .hypothesis/
+.pytest_cache/
 
 # Translations
 *.mo
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 5022499..72a37cd 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,6 +1,15 @@
 Changelog
 =========
 
+.. _v0-3-0:
+
+0.3.0 - 2019-02-24 
+~~~~~~~~~~~~~~~~~~
+
+* Added support for non-default crypto backends
+* Loosened restriction on Cryptography version in requirements.txt and bumped version to 2.5
+* Moved away from custom x448 implementation in favor of OpenSSL implementation (for default backend)   
+
 .. _v0-2-2:
 
 0.2.2 - 2018-03-21
@@ -35,4 +44,4 @@ Changelog
 0.1.1 - 2017-09-12
 ~~~~~~~~~~~~~~~~~~
 
-Initial release.
\ No newline at end of file
+Initial release.
diff --git a/README.md b/README.md
index 67e9bd1..bae17c9 100755
--- a/README.md
+++ b/README.md
@@ -10,10 +10,6 @@ Compatible with revisions 32 and 33.
 
 Master branch contains latest version released. Trunk branch is an active development branch.
 
-### Warning
-This package shall not be used (yet) for production purposes. There was little to none peer review done so far. 
-Use common sense while using - until this package becomes stable.
-
 ## Documentation
 Available on [Read the Docs](https://noiseprotocol.readthedocs.io). For now it provides basic documentation on 
 HandshakeState, CipherState and SymmetricState. Refer to the rest of the README below for more information.
@@ -138,12 +134,12 @@ pytest
 
 ### Todo-list for the project:
 
-- [ ] custom crypto backends
+- [x] add non-default crypto algorithms support, as requested
 - [ ] fallback patterns support
 - [ ] scripts for keypair generation (+ console entry points)
 - [ ] "echo" (noise-c like) example
 - [ ] extensive logging
-- [ ] move away from custom ed448 implementation
+- [x] move away from custom ed448 implementation
 - [ ] implement countermeasures for side-channel attacks
 - [ ] **get peer review of the code**
 
diff --git a/docs/conf.py b/docs/conf.py
index bfc8e94..996cf2a 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -58,9 +58,9 @@ author = 'Piotr Lizonczyk'
 # built documents.
 #
 # The short X.Y version.
-version = '0.2'
+version = '0.3'
 # The full version, including alpha/beta/rc tags.
-release = '0.2.0'
+release = '0.3.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
diff --git a/noise/backends/__init__.py b/noise/backends/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/noise/backends/default/__init__.py b/noise/backends/default/__init__.py
new file mode 100644
index 0000000..bd0305e
--- /dev/null
+++ b/noise/backends/default/__init__.py
@@ -0,0 +1,3 @@
+from .backend import DefaultNoiseBackend
+
+noise_backend = DefaultNoiseBackend()
diff --git a/noise/backends/default/backend.py b/noise/backends/default/backend.py
new file mode 100644
index 0000000..e6bc780
--- /dev/null
+++ b/noise/backends/default/backend.py
@@ -0,0 +1,38 @@
+from noise.backends.default.ciphers import ChaCha20Cipher, AESGCMCipher
+from noise.backends.default.diffie_hellmans import ED25519, ED448
+from noise.backends.default.hashes import hmac_hash, BLAKE2sHash, BLAKE2bHash, SHA256Hash, SHA512Hash
+from noise.backends.default.keypairs import KeyPair25519, KeyPair448
+from noise.backends.noise_backend import NoiseBackend
+
+
+class DefaultNoiseBackend(NoiseBackend):
+    """
+    Contains all the crypto methods endorsed by Noise Protocol specification, using Cryptography as backend
+    """
+
+    def __init__(self):
+        super(DefaultNoiseBackend, self).__init__()
+
+        self.diffie_hellmans = {
+            '25519': ED25519,
+            '448': ED448
+        }
+
+        self.ciphers = {
+            'AESGCM': AESGCMCipher,
+            'ChaChaPoly': ChaCha20Cipher
+        }
+
+        self.hashes = {
+            'BLAKE2s': BLAKE2sHash,
+            'BLAKE2b': BLAKE2bHash,
+            'SHA256': SHA256Hash,
+            'SHA512': SHA512Hash
+        }
+
+        self.keypairs = {
+            '25519': KeyPair25519,
+            '448': KeyPair448
+        }
+
+        self.hmac = hmac_hash
diff --git a/noise/backends/default/ciphers.py b/noise/backends/default/ciphers.py
new file mode 100644
index 0000000..9360125
--- /dev/null
+++ b/noise/backends/default/ciphers.py
@@ -0,0 +1,35 @@
+import abc
+
+from cryptography.hazmat.primitives.ciphers.aead import AESGCM, ChaCha20Poly1305
+
+from noise.functions.cipher import Cipher
+
+
+class CryptographyCipher(Cipher, metaclass=abc.ABCMeta):
+    def encrypt(self, k, n, ad, plaintext):
+        return self.cipher.encrypt(nonce=self.format_nonce(n), data=plaintext, associated_data=ad)
+
+    def decrypt(self, k, n, ad, ciphertext):
+        return self.cipher.decrypt(nonce=self.format_nonce(n), data=ciphertext, associated_data=ad)
+
+    @abc.abstractmethod
+    def format_nonce(self, n):
+        raise NotImplementedError
+
+
+class AESGCMCipher(CryptographyCipher):
+    @property
+    def klass(self):
+        return AESGCM
+
+    def format_nonce(self, n):
+        return b'\x00\x00\x00\x00' + n.to_bytes(length=8, byteorder='big')
+
+
+class ChaCha20Cipher(CryptographyCipher):
+    @property
+    def klass(self):
+        return ChaCha20Poly1305
+
+    def format_nonce(self, n):
+        return b'\x00\x00\x00\x00' + n.to_bytes(length=8, byteorder='little')
diff --git a/noise/backends/default/diffie_hellmans.py b/noise/backends/default/diffie_hellmans.py
new file mode 100644
index 0000000..5ddbc65
--- /dev/null
+++ b/noise/backends/default/diffie_hellmans.py
@@ -0,0 +1,45 @@
+from cryptography.hazmat.primitives.asymmetric import x25519, x448
+
+from noise.backends.default.keypairs import KeyPair25519, KeyPair448
+from noise.exceptions import NoiseValueError
+from noise.functions.dh import DH
+
+
+class ED25519(DH):
+    @property
+    def klass(self):
+        return KeyPair25519
+
+    @property
+    def dhlen(self):
+        return 32
+
+    def generate_keypair(self) -> 'KeyPair':
+        private_key = x25519.X25519PrivateKey.generate()
+        public_key = private_key.public_key()
+        return KeyPair25519(private_key, public_key, public_key.public_bytes())
+
+    def dh(self, private_key, public_key) -> bytes:
+        if not isinstance(private_key, x25519.X25519PrivateKey) or not isinstance(public_key, x25519.X25519PublicKey):
+            raise NoiseValueError('Invalid keys! Must be x25519.X25519PrivateKey and x25519.X25519PublicKey instances')
+        return private_key.exchange(public_key)
+
+
+class ED448(DH):
+    @property
+    def klass(self):
+        return KeyPair448
+
+    @property
+    def dhlen(self):
+        return 56
+
+    def generate_keypair(self) -> 'KeyPair':
+        private_key = x448.X448PrivateKey.generate()
+        public_key = private_key.public_key()
+        return KeyPair448(private_key, public_key, public_key.public_bytes())
+
+    def dh(self, private_key, public_key) -> bytes:
+        if not isinstance(private_key, x448.X448PrivateKey) or not isinstance(public_key, x448.X448PublicKey):
+            raise NoiseValueError('Invalid keys! Must be x448.X448PrivateKey and x448.X448PublicKey instances')
+        return private_key.exchange(public_key)
diff --git a/noise/backends/default/hashes.py b/noise/backends/default/hashes.py
new file mode 100644
index 0000000..4fae13c
--- /dev/null
+++ b/noise/backends/default/hashes.py
@@ -0,0 +1,80 @@
+import abc
+from functools import partial
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.hmac import HMAC
+
+from noise.functions.hash import Hash
+
+cryptography_backend = default_backend()
+
+
+class CryptographyHash(Hash, metaclass=abc.ABCMeta):
+    def hash(self, data):
+        digest = hashes.Hash(self.fn(), cryptography_backend)
+        digest.update(data)
+        return digest.finalize()
+
+
+class SHA256Hash(CryptographyHash):
+    @property
+    def fn(self):
+        return hashes.SHA256
+
+    @property
+    def hashlen(self):
+        return 32
+
+    @property
+    def blocklen(self):
+        return 64
+
+
+class SHA512Hash(CryptographyHash):
+    @property
+    def fn(self):
+        return hashes.SHA512
+
+    @property
+    def hashlen(self):
+        return 64
+
+    @property
+    def blocklen(self):
+        return 128
+
+
+class BLAKE2sHash(CryptographyHash):
+    @property
+    def fn(self):
+        return partial(hashes.BLAKE2s, digest_size=self.hashlen)
+
+    @property
+    def hashlen(self):
+        return 32
+
+    @property
+    def blocklen(self):
+        return 64
+
+
+class BLAKE2bHash(CryptographyHash):
+    @property
+    def fn(self):
+        return partial(hashes.BLAKE2b, digest_size=self.hashlen)
+
+    @property
+    def hashlen(self):
+        return 64
+
+    @property
+    def blocklen(self):
+        return 128
+
+
+def hmac_hash(key, data, algorithm):
+    # Applies HMAC using the HASH() function.
+    hmac = HMAC(key=key, algorithm=algorithm(), backend=cryptography_backend)
+    hmac.update(data=data)
+    return hmac.finalize()
diff --git a/noise/backends/default/keypairs.py b/noise/backends/default/keypairs.py
new file mode 100644
index 0000000..5e74ddf
--- /dev/null
+++ b/noise/backends/default/keypairs.py
@@ -0,0 +1,39 @@
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric import x25519, x448
+
+from noise.exceptions import NoiseValueError
+from noise.functions.keypair import KeyPair
+
+
+class KeyPair25519(KeyPair):
+    @classmethod
+    def from_private_bytes(cls, private_bytes):
+        if len(private_bytes) != 32:
+            raise NoiseValueError('Invalid length of private_bytes! Should be 32')
+        private = x25519.X25519PrivateKey.from_private_bytes(private_bytes)
+        public = private.public_key()
+        return cls(private=private, public=public, public_bytes=public.public_bytes(encoding=serialization.Encoding.Raw, format=serialization.PublicFormat.Raw))
+
+    @classmethod
+    def from_public_bytes(cls, public_bytes):
+        if len(public_bytes) != 32:
+            raise NoiseValueError('Invalid length of public_bytes! Should be 32')
+        public = x25519.X25519PublicKey.from_public_bytes(public_bytes)
+        return cls(public=public, public_bytes=public.public_bytes(encoding=serialization.Encoding.Raw, format=serialization.PublicFormat.Raw))
+
+
+class KeyPair448(KeyPair):
+    @classmethod
+    def from_private_bytes(cls, private_bytes):
+        if len(private_bytes) != 56:
+            raise NoiseValueError('Invalid length of private_bytes! Should be 56')
+        private = x448.X448PrivateKey.from_private_bytes(private_bytes)
+        public = private.public_key()
+        return cls(private=private, public=public, public_bytes=public.public_bytes(encoding=serialization.Encoding.Raw, format=serialization.PublicFormat.Raw))
+
+    @classmethod
+    def from_public_bytes(cls, public_bytes):
+        if len(public_bytes) != 56:
+            raise NoiseValueError('Invalid length of private_bytes! Should be 56')
+        public = x448.X448PublicKey.from_public_bytes(public_bytes)
+        return cls(public=public, public_bytes=public.public_bytes(encoding=serialization.Encoding.Raw, format=serialization.PublicFormat.Raw))
diff --git a/noise/backends/experimental/__init__.py b/noise/backends/experimental/__init__.py
new file mode 100644
index 0000000..08f0344
--- /dev/null
+++ b/noise/backends/experimental/__init__.py
@@ -0,0 +1,3 @@
+from noise.backends.experimental.backend import ExperimentalNoiseBackend
+
+noise_backend = ExperimentalNoiseBackend()
diff --git a/noise/backends/experimental/backend.py b/noise/backends/experimental/backend.py
new file mode 100644
index 0000000..e065b5f
--- /dev/null
+++ b/noise/backends/experimental/backend.py
@@ -0,0 +1,8 @@
+from noise.backends.default import DefaultNoiseBackend
+
+
+class ExperimentalNoiseBackend(DefaultNoiseBackend):
+    """
+    Contains all the default crypto methods, but also methods not directly endorsed by Noise Protocol specification
+    """
+    pass
diff --git a/noise/backends/noise_backend.py b/noise/backends/noise_backend.py
new file mode 100644
index 0000000..d172036
--- /dev/null
+++ b/noise/backends/noise_backend.py
@@ -0,0 +1,64 @@
+from noise.exceptions import NoiseProtocolNameError
+from noise.functions.hash import hkdf
+from noise.patterns import (PatternN, PatternK, PatternX, PatternNN, PatternKN, PatternNK, PatternKK, PatternNX,
+                            PatternKX, PatternXN, PatternIN, PatternXK, PatternIK, PatternXX, PatternIX)
+
+
+class NoiseBackend:
+    """
+    Base for creating backends.
+    Implementing classes must define supported crypto methods in appropriate dict (diffie_hellmans, ciphers, etc.)
+    HMAC function must be defined as well.
+
+    Dicts use convention for keys - they must match the string that occurs in Noise Protocol name.
+    """
+    def __init__(self):
+        self.patterns = {
+            'N': PatternN,
+            'K': PatternK,
+            'X': PatternX,
+            'NN': PatternNN,
+            'KN': PatternKN,
+            'NK': PatternNK,
+            'KK': PatternKK,
+            'NX': PatternNX,
+            'KX': PatternKX,
+            'XN': PatternXN,
+            'IN': PatternIN,
+            'XK': PatternXK,
+            'IK': PatternIK,
+            'XX': PatternXX,
+            'IX': PatternIX,
+        }
+
+        self.diffie_hellmans = {}
+        self.ciphers = {}
+        self.hashes = {}
+        self.keypairs = {}
+        self.hmac = None
+
+        self.hkdf = hkdf
+
+    @property
+    def methods(self):
+        return {
+            'pattern': self.patterns,
+            'dh': self.diffie_hellmans,
+            'cipher': self.ciphers,
+            'hash': self.hashes,
+            'keypair': self.keypairs
+        }
+
+    def map_protocol_name_to_crypto(self, unpacked_name):
+        mappings = {}
+        # Validate if we know everything that Noise Protocol is supposed to use and map appropriate functions
+        for method, map_dict in self.methods.items():
+            looked_up_func = getattr(unpacked_name, method)
+            func = map_dict.get(looked_up_func)
+            if not func:
+                raise NoiseProtocolNameError('Unknown {} in Noise Protocol name, given {}, known {}'.format(
+                                             method, looked_up_func, " ".join(map_dict)))
+            mappings[method] = func
+
+        return mappings
+
diff --git a/noise/connection.py b/noise/connection.py
index 3f5dd58..3e64c7f 100644
--- a/noise/connection.py
+++ b/noise/connection.py
@@ -3,6 +3,7 @@ from typing import Union, List
 
 from cryptography.exceptions import InvalidTag
 
+from noise.backends.default import noise_backend
 from noise.constants import MAX_MESSAGE_LEN
 from noise.exceptions import NoisePSKError, NoiseValueError, NoiseHandshakeError, NoiseInvalidMessage
 from .noise_protocol import NoiseProtocol
@@ -21,6 +22,7 @@ _keypairs = {Keypair.STATIC: 's', Keypair.REMOTE_STATIC: 'rs',
 
 class NoiseConnection(object):
     def __init__(self):
+        self.backend = None
         self.noise_protocol = None
         self.protocol_name = None
         self.handshake_finished = False
@@ -28,14 +30,14 @@ class NoiseConnection(object):
         self._next_fn = None
 
     @classmethod
-    def from_name(cls, name: Union[str, bytes]):
+    def from_name(cls, name: Union[str, bytes], backend=noise_backend):
         instance = cls()
         # Forgiving passing string. Bytes are good too, anything else will fail inside NoiseProtocol
         try:
             instance.protocol_name = name.encode('ascii') if isinstance(name, str) else name
         except ValueError:
             raise NoiseValueError('If passing string as protocol name, it must contain only ASCII characters')
-        instance.noise_protocol = NoiseProtocol(protocol_name=name)
+        instance.noise_protocol = NoiseProtocol(protocol_name=name, backend=backend)
         return instance
 
     def set_psks(self, psk: Union[bytes, str] = None, psks: List[Union[str, bytes]] = None):
@@ -74,21 +76,21 @@ class NoiseConnection(object):
 
     def set_keypair_from_private_bytes(self, keypair: Keypair, private_bytes: bytes):
         self.noise_protocol.keypairs[_keypairs[keypair]] = \
-            self.noise_protocol.dh_fn.keypair_cls.from_private_bytes(private_bytes)
+            self.noise_protocol.dh_fn.klass.from_private_bytes(private_bytes)
 
     def set_keypair_from_public_bytes(self, keypair: Keypair, private_bytes: bytes):
         self.noise_protocol.keypairs[_keypairs[keypair]] = \
-            self.noise_protocol.dh_fn.keypair_cls.from_public_bytes(private_bytes)
+            self.noise_protocol.dh_fn.klass.from_public_bytes(private_bytes)
 
     def set_keypair_from_private_path(self, keypair: Keypair, path: str):
         with open(path, 'rb') as fd:
             self.noise_protocol.keypairs[_keypairs[keypair]] = \
-                self.noise_protocol.dh_fn.keypair_cls.from_private_bytes(fd.read())
+                self.noise_protocol.dh_fn.klass.from_private_bytes(fd.read())
 
     def set_keypair_from_public_path(self, keypair: Keypair, path: str):
         with open(path, 'rb') as fd:
             self.noise_protocol.keypairs[_keypairs[keypair]] = \
-                self.noise_protocol.dh_fn.keypair_cls.from_public_bytes(fd.read())
+                self.noise_protocol.dh_fn.klass.from_public_bytes(fd.read())
 
     def start_handshake(self):
         self.noise_protocol.validate()
diff --git a/noise/crypto.py b/noise/crypto.py
deleted file mode 100644
index c47f522..0000000
--- a/noise/crypto.py
+++ /dev/null
@@ -1,110 +0,0 @@
-DHLEN = 56
-P = 2 ** 448 - 2 ** 224 - 1
-A24 = 39081
-
-
-class X448(object):
-    # Based on RFC 7748 and heavily relying on it - https://tools.ietf.org/html/rfc7748#section-5
-    # Modified mostly to fulfill python3 changes
-    # Almost surely unsafe from side-channel attacks.
-    # Should be replaced with safer implementation (most likely one from OpenSSL and/or pyca/Cryptography)
-    @staticmethod
-    def decode_little_endian(b):
-        assert len(b) == DHLEN
-        return sum([b[i] << 8 * i for i in range(DHLEN)])
-
-    @staticmethod
-    def decode_u_coordinate(u):
-        u[-1] &= (1 << 56) - 1
-        return X448.decode_little_endian(u)
-
-    @staticmethod
-    def encode_u_coordinate(u):
-        return bytes([(u >> 8 * i) & 255 for i in range(DHLEN)])
-
-    @staticmethod
-    def decode_scalar448(k):
-        k = [b for b in k]
-        k[0] &= 252
-        k[55] |= 128
-        return X448.decode_little_endian(k)
-
-    @staticmethod
-    def cswap(swap, x2, x3):
-        dummy = (swap * (x2 - x3)) % P
-        x2 = (x2 - dummy) % P
-        x3 = (x3 + dummy) % P
-        return x2, x3
-
-    @staticmethod
-    def x448(k, u):
-        x1 = u
-        x2 = 1
-        z2 = 0
-        x3 = u
-        z3 = 1
-        swap = 0
-
-        for t in range(448-1, -1, -1):
-            k_t = (k >> t) & 1
-            swap ^= k_t
-            x2, x3 = X448.cswap(swap, x2, x3)
-            z2, z3 = X448.cswap(swap, z2, z3)
-            swap = k_t
-
-            a = (x2 + z2) % P
-            aa = (a * a) % P
-            b = (x2 - z2) % P
-            bb = (b * b) % P
-            e = (aa - bb) % P
-            c = (x3 + z3) % P
-            d = (x3 - z3) % P
-            da = (d * a) % P
-            cb = (c * b) % P
-            x3 = pow((da + cb) % P, 2, P)
-            z3 = (x1 * pow((da - cb) % P, 2, P)) % P
-            x2 = (aa * bb) % P
-            z2 = (e * ((aa + (A24 * e) % P) % P)) % P
-
-        x2, x3 = X448.cswap(swap, x2, x3)
-        z2, z3 = X448.cswap(swap, z2, z3)
-
-        return (x2 * pow(z2, P - 2, P)) % P
-
-    @staticmethod
-    def mul(n, p):
-        return X448.encode_u_coordinate(X448.x448(X448.decode_scalar448(n), X448.decode_little_endian(p)))
-
-    @staticmethod
-    def mul_5(n):
-        return X448.encode_u_coordinate(X448.x448(X448.decode_scalar448(n), 5))
-
-
-# Self-test
-# Test vectors taken from RFC 7748 section 5.2 and 6.2
-scalar1 = bytes.fromhex(
-    '203d494428b8399352665ddca42f9de8fef600908e0d461cb021f8c538345dd77c3e4806e25f46d3315c44e0a5b4371282dd2c8d5be3095f')
-u1 = bytes.fromhex(
-    '0fbcc2f993cd56d3305b0b7d9e55d4c1a8fb5dbb52f8e9a1e9b6201b165d015894e56c4d3570bee52fe205e28a78b91cdfbde71ce8d157db')
-assert X448.mul(scalar1, u1) == bytes.fromhex(
-    '884a02576239ff7a2f2f63b2db6a9ff37047ac13568e1e30fe63c4a7ad1b3ee3a5700df34321d62077e63633c575c1c954514e99da7c179d')
-
-scalar2 = bytes.fromhex(
-    '3d262fddf9ec8e88495266fea19a34d28882acef045104d0d1aae121700a779c984c24f8cdd78fbff44943eba368f54b29259a4f1c600ad3')
-u2 = bytes.fromhex(
-    '06fce640fa3487bfda5f6cf2d5263f8aad88334cbd07437f020f08f9814dc031ddbdc38c19c6da2583fa5429db94ada18aa7a7fb4ef8a086')
-assert X448.mul(scalar2, u2) == bytes.fromhex(
-    'ce3e4ff95a60dc6697da1db1d85e6afbdf79b50a2412d7546d5f239fe14fbaadeb445fc66a01b0779d98223961111e21766282f73dd96b6f')
-
-alice_priv = bytes.fromhex(
-    '9a8f4925d1519f5775cf46b04b5800d4ee9ee8bae8bc5565d498c28dd9c9baf574a9419744897391006382a6f127ab1d9ac2d8c0a598726b')
-alice_pub = bytes.fromhex(
-    '9b08f7cc31b7e3e67d22d5aea121074a273bd2b83de09c63faa73d2c22c5d9bbc836647241d953d40c5b12da88120d53177f80e532c41fa0')
-bob_priv = bytes.fromhex(
-    '1c306a7ac2a0e2e0990b294470cba339e6453772b075811d8fad0d1d6927c120bb5ee8972b0d3e21374c9c921b09d1b0366f10b65173992d')
-bob_pub = bytes.fromhex(
-    '3eb7a829b0cd20f5bcfc0b599b6feccf6da4627107bdb0d4f345b43027d8b972fc3e34fb4232a13ca706dcb57aec3dae07bdc1c67bf33609')
-assert alice_pub == X448.mul_5(alice_priv)
-assert bob_pub == X448.mul_5(bob_priv)
-assert X448.mul(alice_priv, bob_pub) == X448.mul(bob_priv, alice_pub) == bytes.fromhex(
-    '07fff4181ac6cc95ec1c16a94a0f74d12da232ce40a77552281d282bb60c0b56fd2464c335543936521c24403085d59a449a5037514a879d')
diff --git a/noise/functions.py b/noise/functions.py
deleted file mode 100644
index 72e48a2..0000000
--- a/noise/functions.py
+++ /dev/null
@@ -1,251 +0,0 @@
-import abc
-import warnings
-from functools import partial
-import os
-
-from cryptography.hazmat.backends import default_backend
-from cryptography.hazmat.primitives import hashes
-from cryptography.hazmat.primitives.asymmetric import x25519
-from cryptography.hazmat.primitives.ciphers.aead import AESGCM, ChaCha20Poly1305
-from cryptography.hazmat.primitives.hmac import HMAC
-from noise.constants import MAX_NONCE
-from noise.exceptions import NoiseValueError
-from .crypto import X448
-
-backend = default_backend()
-
-
-class DH(object):
-    def __init__(self, method):
-        if method == 'ed25519':
-            self.method = method
-            self.dhlen = 32
-            self.keypair_cls = KeyPair25519
-            self.generate_keypair = self._25519_generate_keypair
-            self.dh = self._25519_dh
-        elif method == 'ed448':
-            self.method = method
-            self.dhlen = 56
-            self.keypair_cls = KeyPair448
-            self.generate_keypair = self._448_generate_keypair
-            self.dh = self._448_dh
-        else:
-            raise NotImplementedError('DH method: {}'.format(method))
-
-    def _25519_generate_keypair(self) -> '_KeyPair':
-        private_key = x25519.X25519PrivateKey.generate()
-        public_key = private_key.public_key()
-        return KeyPair25519(private_key, public_key, public_key.public_bytes())
-
-    def _25519_dh(self, private_key: 'x25519.X25519PrivateKey', public_key: 'x25519.X25519PublicKey') -> bytes:
-        if not isinstance(private_key, x25519.X25519PrivateKey) or not isinstance(public_key, x25519.X25519PublicKey):
-            raise NoiseValueError('Invalid keys! Must be x25519.X25519PrivateKey and x25519.X25519PublicKey instances')
-        return private_key.exchange(public_key)
-
-    def _448_generate_keypair(self) -> '_KeyPair':
-        return KeyPair448.new()
-
-    def _448_dh(self, private_key: bytes, public_key: bytes) -> bytes:
-        if len(private_key) != self.dhlen or len(public_key) != self.dhlen:
-            raise NoiseValueError('Invalid length of keys! Should be {}'.format(self.dhlen))
-        return X448.mul(private_key, public_key)
-
-
-class Cipher(object):
-    def __init__(self, method):
-        if method == 'AESGCM':
-            self._cipher = AESGCM
-            self.encrypt = self._aesgcm_encrypt
-            self.decrypt = self._aesgcm_decrypt
-            self.rekey = self._default_rekey
-        elif method == 'ChaCha20':
-            self._cipher = ChaCha20Poly1305
-            self.encrypt = self._chacha20_encrypt
-            self.decrypt = self._chacha20_decrypt
-            self.rekey = self._default_rekey
-        else:
-            raise NotImplementedError('Cipher method: {}'.format(method))
-        self.cipher = None
-
-    def _aesgcm_encrypt(self, k, n, ad, plaintext):
-        return self.cipher.encrypt(nonce=self._aesgcm_nonce(n), data=plaintext, associated_data=ad)
-
-    def _aesgcm_decrypt(self, k, n, ad, ciphertext):
-        return self.cipher.decrypt(nonce=self._aesgcm_nonce(n), data=ciphertext, associated_data=ad)
-
-    def _aesgcm_nonce(self, n):
-        return b'\x00\x00\x00\x00' + n.to_bytes(length=8, byteorder='big')
-
-    def _chacha20_encrypt(self, k, n, ad, plaintext):
-        return self.cipher.encrypt(nonce=self._chacha20_nonce(n), data=plaintext, associated_data=ad)
-
-    def _chacha20_decrypt(self, k, n, ad, ciphertext):
-        return self.cipher.decrypt(nonce=self._chacha20_nonce(n), data=ciphertext, associated_data=ad)
-
-    def _chacha20_nonce(self, n):
-        return b'\x00\x00\x00\x00' + n.to_bytes(length=8, byteorder='little')
-
-    def _default_rekey(self, k):
-        return self.encrypt(k, MAX_NONCE, b'', b'\x00' * 32)[:32]
-
-    def initialize(self, key):
-        self.cipher = self._cipher(key)
-
-
-class Hash(object):
-    def __init__(self, method):
-        if method == 'SHA256':
-            self.hashlen = 32
-            self.blocklen = 64
-            self.hash = self._hash_sha256
-            self.fn = hashes.SHA256
-        elif method == 'SHA512':
-            self.hashlen = 64
-            self.blocklen = 128
-            self.hash = self._hash_sha512
-            self.fn = hashes.SHA512
-        elif method == 'BLAKE2s':
-            self.hashlen = 32
-            self.blocklen = 64
-            self.hash = self._hash_blake2s
-            self.fn = partial(hashes.BLAKE2s, digest_size=self.hashlen)
-        elif method == 'BLAKE2b':
-            self.hashlen = 64
-            self.blocklen = 128
-            self.hash = self._hash_blake2b
-            self.fn = partial(hashes.BLAKE2b, digest_size=self.hashlen)
-        else:
-            raise NotImplementedError('Hash method: {}'.format(method))
-
-    def _hash_sha256(self, data):
-        digest = hashes.Hash(hashes.SHA256(), backend)
-        digest.update(data)
-        return digest.finalize()
-
-    def _hash_sha512(self, data):
-        digest = hashes.Hash(hashes.SHA512(), backend)
-        digest.update(data)
-        return digest.finalize()
-
-    def _hash_blake2s(self, data):
-        digest = hashes.Hash(hashes.BLAKE2s(digest_size=self.hashlen), backend)
-        digest.update(data)
-        return digest.finalize()
-
-    def _hash_blake2b(self, data):
-        digest = hashes.Hash(hashes.BLAKE2b(digest_size=self.hashlen), backend)
-        digest.update(data)
-        return digest.finalize()
-
-
-class _KeyPair(object):
-    __metaclass__ = abc.ABCMeta
-
-    def __init__(self, private=None, public=None, public_bytes=None):
-        self.private = private
-        self.public = public
-        self.public_bytes = public_bytes
-
-    @classmethod
-    @abc.abstractmethod
-    def from_private_bytes(cls, private_bytes):
-        raise NotImplementedError
-
-    @classmethod
-    @abc.abstractmethod
-    def from_public_bytes(cls, public_bytes):
-        raise NotImplementedError
-
-
-class KeyPair25519(_KeyPair):
-    @classmethod
-    def from_private_bytes(cls, private_bytes):
-        if len(private_bytes) != 32:
-            raise NoiseValueError('Invalid length of private_bytes! Should be 32')
-        private = x25519.X25519PrivateKey.from_private_bytes(private_bytes)
-        public = private.public_key()
-        return cls(private=private, public=public, public_bytes=public.public_bytes())
-
-    @classmethod
-    def from_public_bytes(cls, public_bytes):
-        if len(public_bytes) != 32:
-            raise NoiseValueError('Invalid length of public_bytes! Should be 32')
-        public = x25519.X25519PublicKey.from_public_bytes(public_bytes)
-        return cls(public=public, public_bytes=public.public_bytes())
-
-
-class KeyPair448(_KeyPair):
-    def __init__(self, *args, **kwargs):
-        super(KeyPair448, self).__init__(*args, **kwargs)
-        warnings.warn('This implementation of ed448 is likely to be very insecure! USE ONLY FOR TESTING!')
-
-    @classmethod
-    def from_private_bytes(cls, private_bytes):
-        if len(private_bytes) != 56:
-            raise NoiseValueError('Invalid length of private_bytes! Should be 56')
-        private = private_bytes
-        public = X448.mul_5(private)
-        return cls(private=private, public=public, public_bytes=public)
-
-    @classmethod
-    def from_public_bytes(cls, public_bytes):
-        if len(public_bytes) != 56:
-            raise NoiseValueError('Invalid length of private_bytes! Should be 56')
-        return cls(public=public_bytes, public_bytes=public_bytes)
-
-    @classmethod
-    def new(cls):
-        private = os.urandom(56)
-        public = X448.mul_5(private)
-        return cls(private=private, public=public, public_bytes=public)
-
-
-dh_map = {
-    '25519': DH('ed25519'),
-    '448': DH('ed448')
-}
-
-cipher_map = {
-    'AESGCM': partial(Cipher, 'AESGCM'),
-    'ChaChaPoly': partial(Cipher, 'ChaCha20')
-}
-
-hash_map = {
-    'BLAKE2s': Hash('BLAKE2s'),
-    'BLAKE2b': Hash('BLAKE2b'),
-    'SHA256': Hash('SHA256'),
-    'SHA512': Hash('SHA512')
-}
-
-keypair_map = {
-    '25519': KeyPair25519,
-    '448': KeyPair448
-}
-
-
-def hmac_hash(key, data, algorithm):
-    # Applies HMAC using the HASH() function.
-    hmac = HMAC(key=key, algorithm=algorithm(), backend=backend)
-    hmac.update(data=data)
-    return hmac.finalize()
-
-
-def hkdf(chaining_key, input_key_material, num_outputs, hmac_hash_fn):
-    # Sets temp_key = HMAC-HASH(chaining_key, input_key_material).
-    temp_key = hmac_hash_fn(chaining_key, input_key_material)
-
-    # Sets output1 = HMAC-HASH(temp_key, byte(0x01)).
-    output1 = hmac_hash_fn(temp_key, b'\x01')
-
-    # Sets output2 = HMAC-HASH(temp_key, output1 || byte(0x02)).
-    output2 = hmac_hash_fn(temp_key, output1 + b'\x02')
-
-    # If num_outputs == 2 then returns the pair (output1, output2).
-    if num_outputs == 2:
-        return output1, output2
-
-    # Sets output3 = HMAC-HASH(temp_key, output2 || byte(0x03)).
-    output3 = hmac_hash_fn(temp_key, output2 + b'\x03')
-
-    # Returns the triple (output1, output2, output3).
-    return output1, output2, output3
diff --git a/noise/functions/__init__.py b/noise/functions/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/noise/functions/cipher.py b/noise/functions/cipher.py
new file mode 100644
index 0000000..823410a
--- /dev/null
+++ b/noise/functions/cipher.py
@@ -0,0 +1,27 @@
+import abc
+
+from noise.constants import MAX_NONCE
+
+
+class Cipher(metaclass=abc.ABCMeta):
+    def __init__(self):
+        self.cipher = None
+
+    @property
+    @abc.abstractmethod
+    def klass(self):
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def encrypt(self, k, n, ad, plaintext):
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def decrypt(self, k, n, ad, ciphertext):
+        raise NotImplementedError
+
+    def rekey(self, k):
+        return self.encrypt(k, MAX_NONCE, b'', b'\x00' * 32)[:32]
+
+    def initialize(self, key):
+        self.cipher = self.klass(key)
diff --git a/noise/functions/dh.py b/noise/functions/dh.py
new file mode 100644
index 0000000..6b98639
--- /dev/null
+++ b/noise/functions/dh.py
@@ -0,0 +1,21 @@
+import abc
+
+
+class DH(metaclass=abc.ABCMeta):
+    @property
+    @abc.abstractmethod
+    def klass(self):
+        raise NotImplementedError
+
+    @property
+    @abc.abstractmethod
+    def dhlen(self):
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def generate_keypair(self) -> 'KeyPair':
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def dh(self, private_key, public_key) -> bytes:
+        raise NotImplementedError
diff --git a/noise/functions/hash.py b/noise/functions/hash.py
new file mode 100644
index 0000000..76c533c
--- /dev/null
+++ b/noise/functions/hash.py
@@ -0,0 +1,43 @@
+import abc
+
+
+class Hash(metaclass=abc.ABCMeta):
+    @property
+    @abc.abstractmethod
+    def fn(self):
+        raise NotImplementedError
+
+    @property
+    @abc.abstractmethod
+    def hashlen(self):
+        raise NotImplementedError
+
+    @property
+    @abc.abstractmethod
+    def blocklen(self):
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def hash(self, data):
+        raise NotImplementedError
+
+
+def hkdf(chaining_key, input_key_material, num_outputs, hmac_hash_fn):
+    # Sets temp_key = HMAC-HASH(chaining_key, input_key_material).
+    temp_key = hmac_hash_fn(chaining_key, input_key_material)
+
+    # Sets output1 = HMAC-HASH(temp_key, byte(0x01)).
+    output1 = hmac_hash_fn(temp_key, b'\x01')
+
+    # Sets output2 = HMAC-HASH(temp_key, output1 || byte(0x02)).
+    output2 = hmac_hash_fn(temp_key, output1 + b'\x02')
+
+    # If num_outputs == 2 then returns the pair (output1, output2).
+    if num_outputs == 2:
+        return output1, output2
+
+    # Sets output3 = HMAC-HASH(temp_key, output2 || byte(0x03)).
+    output3 = hmac_hash_fn(temp_key, output2 + b'\x03')
+
+    # Returns the triple (output1, output2, output3).
+    return output1, output2, output3
\ No newline at end of file
diff --git a/noise/functions/keypair.py b/noise/functions/keypair.py
new file mode 100644
index 0000000..fa18ff4
--- /dev/null
+++ b/noise/functions/keypair.py
@@ -0,0 +1,18 @@
+import abc
+
+
+class KeyPair(metaclass=abc.ABCMeta):
+    def __init__(self, private=None, public=None, public_bytes=None):
+        self.private = private
+        self.public = public
+        self.public_bytes = public_bytes
+
+    @classmethod
+    @abc.abstractmethod
+    def from_private_bytes(cls, private_bytes):
+        raise NotImplementedError
+
+    @classmethod
+    @abc.abstractmethod
+    def from_public_bytes(cls, public_bytes):
+        raise NotImplementedError
diff --git a/noise/functions/patterns.py b/noise/functions/patterns.py
new file mode 100644
index 0000000..b8c4613
--- /dev/null
+++ b/noise/functions/patterns.py
@@ -0,0 +1,78 @@
+from typing import List
+
+from noise.constants import TOKEN_PSK
+
+
+class Pattern(object):
+    """
+    TODO document
+    """
+    def __init__(self):
+        # As per specification, if both parties have pre-messages, the initiator is listed first. To reduce complexity,
+        # pre_messages shall be a list of two lists:
+        # the first for the initiator's pre-messages, the second for the responder
+        self.pre_messages = [
+            [],
+            []
+        ]
+
+        # List of lists of valid tokens, alternating between tokens for initiator and responder
+        self.tokens = []
+
+        self.name = ''
+        self.one_way = False
+        self.psk_count = 0
+
+    def has_pre_messages(self):
+        return any(map(lambda x: len(x) > 0, self.pre_messages))
+
+    def get_initiator_pre_messages(self) -> list:
+        return self.pre_messages[0].copy()
+
+    def get_responder_pre_messages(self) -> list:
+        return self.pre_messages[1].copy()
+
+    def apply_pattern_modifiers(self, modifiers: List[str]) -> None:
+        # Applies given pattern modifiers to self.tokens of the Pattern instance.
+        for modifier in modifiers:
+            if modifier.startswith('psk'):
+                try:
+                    index = int(modifier.replace('psk', '', 1))
+                except ValueError:
+                    raise ValueError('Improper psk modifier {}'.format(modifier))
+
+                if index // 2 > len(self.tokens):
+                    raise ValueError('Modifier {} cannot be applied - pattern has not enough messages'.format(modifier))
+
+                # Add TOKEN_PSK in the correct place in the correct message
+                if index == 0:  # if 0, insert at the beginning of first message
+                    self.tokens[0].insert(0, TOKEN_PSK)
+                else:  # if bigger than zero, append at the end of first, second etc.
+                    self.tokens[index - 1].append(TOKEN_PSK)
+                self.psk_count += 1
+
+            elif modifier == 'fallback':
+                raise NotImplementedError  # TODO implement
+
+            else:
+                raise ValueError('Unknown pattern modifier {}'.format(modifier))
+
+    def get_required_keypairs(self, initiator: bool) -> list:
+        required = []
+        if initiator:
+            if self.name[0] in ('K', 'X', 'I'):
+                required.append('s')
+            if self.one_way or self.name[1] == 'K':
+                required.append('rs')
+        else:
+            if self.name[0] == 'K':
+                required.append('rs')
+            if self.one_way or self.name[1] in ['K', 'X']:
+                required.append('s')
+        return required
+
+
+class OneWayPattern(Pattern):
+    def __init__(self):
+        super(OneWayPattern, self).__init__()
+        self.one_way = True
diff --git a/noise/noise_protocol.py b/noise/noise_protocol.py
index c3ad8da..3eb065e 100644
--- a/noise/noise_protocol.py
+++ b/noise/noise_protocol.py
@@ -5,48 +5,37 @@ from typing import Tuple
 from noise.exceptions import NoiseProtocolNameError, NoisePSKError, NoiseValidationError
 from noise.state import HandshakeState
 from .constants import MAX_PROTOCOL_NAME_LEN, Empty
-from .functions import dh_map, cipher_map, hash_map, keypair_map, hmac_hash, hkdf
-from .patterns import patterns_map
 
 
 class NoiseProtocol(object):
     """
     TODO: Document
     """
-    methods = {
-        'pattern': patterns_map,
-        'dh': dh_map,
-        'cipher': cipher_map,
-        'hash': hash_map,
-        'keypair': keypair_map
-    }
-
-    def __init__(self, protocol_name: bytes):
-        if not isinstance(protocol_name, bytes):
-            raise NoiseProtocolNameError('Protocol name has to be of type "bytes" not {}'.format(type(protocol_name)))
-        if len(protocol_name) > MAX_PROTOCOL_NAME_LEN:
-            raise NoiseProtocolNameError('Protocol name too long, has to be at most '
-                                         '{} chars long'.format(MAX_PROTOCOL_NAME_LEN))
-
+    def __init__(self, protocol_name: bytes, backend: 'NoiseBackend'):
         self.name = protocol_name
-        mappings, pattern_modifiers = self._parse_protocol_name()
+        self.backend = backend
+        unpacked_name = UnpackedName.from_protocol_name(self.name)
+        mappings = self.backend.map_protocol_name_to_crypto(unpacked_name)
 
         # A valid Pattern instance (see Section 7 of specification (rev 32))
         self.pattern = mappings['pattern']()
-        self.pattern_modifiers = pattern_modifiers
+        self.pattern_modifiers = unpacked_name.pattern_modifiers
         if self.pattern_modifiers:
-            self.pattern.apply_pattern_modifiers(pattern_modifiers)
+            self.pattern.apply_pattern_modifiers(self.pattern_modifiers)
 
         # Handle PSK handshake options
         self.psks = None
         self.is_psk_handshake = any([modifier.startswith('psk') for modifier in self.pattern_modifiers])
 
-        self.dh_fn = mappings['dh']
-        self.cipher_fn = mappings['cipher']
-        self.hash_fn = mappings['hash']
-        self.keypair_fn = mappings['keypair']
-        self.hmac = partial(hmac_hash, algorithm=self.hash_fn.fn)
-        self.hkdf = partial(hkdf, hmac_hash_fn=self.hmac)
+        # Preinitialized
+        self.dh_fn = mappings['dh']()
+        self.hash_fn = mappings['hash']()
+        self.hmac = partial(backend.hmac, algorithm=self.hash_fn.fn)
+        self.hkdf = partial(backend.hkdf, hmac_hash_fn=self.hmac)
+
+        # Initialized where needed
+        self.cipher_class = mappings['cipher']
+        self.keypair_class = mappings['keypair']
 
         self.prologue = None
         self.initiator = None
@@ -60,42 +49,6 @@ class NoiseProtocol(object):
 
         self.keypairs = {'s': None, 'e': None, 'rs': None, 're': None}
 
-    def _parse_protocol_name(self) -> Tuple[dict, list]:
-        unpacked = self.name.decode().split('_')
-        if unpacked[0] != 'Noise':
-            raise NoiseProtocolNameError('Noise Protocol name shall begin with Noise! Provided: {}'.format(self.name))
-
-        # Extract pattern name and pattern modifiers
-        pattern = ''
-        modifiers_str = None
-        for i, char in enumerate(unpacked[1]):
-            if char.isupper():
-                pattern += char
-            else:
-                # End of pattern, now look for modifiers
-                modifiers_str = unpacked[1][i:]  # Will be empty string if it exceeds string size
-                break
-        modifiers = modifiers_str.split('+') if modifiers_str else []
-
-        data = {'pattern': 'Pattern' + pattern,
-                'dh': unpacked[2],
-                'cipher': unpacked[3],
-                'hash': unpacked[4],
-                'keypair': unpacked[2],
-                'pattern_modifiers': modifiers}
-
-        mapped_data = {}
-
-        # Validate if we know everything that Noise Protocol is supposed to use and map appropriate functions
-        for key, map_dict in self.methods.items():
-            func = map_dict.get(data[key])
-            if not func:
-                raise NoiseProtocolNameError('Unknown {} in Noise Protocol name, given {}, known {}'.format(
-                                             key, data[key], " ".join(map_dict)))
-            mapped_data[key] = func
-
-        return mapped_data, modifiers
-
     def handshake_done(self):
         if self.pattern.one_way:
             if self.initiator:
@@ -110,7 +63,7 @@ class NoiseProtocol(object):
         del self.initiator
         del self.dh_fn
         del self.hash_fn
-        del self.keypair_fn
+        del self.keypair_class
 
     def validate(self):
         if self.is_psk_handshake:
@@ -141,3 +94,46 @@ class NoiseProtocol(object):
                 kwargs[keypair] = value
         self.handshake_state = HandshakeState.initialize(self, **kwargs)
         self.symmetric_state = self.handshake_state.symmetric_state
+
+
+class UnpackedName:
+    def __init__(self, pattern, dh, cipher, hash, keypair, pattern_modifiers):
+        self.pattern = pattern
+        self.dh = dh
+        self.cipher = cipher
+        self.hash = hash
+        self.keypair = keypair
+        self.pattern_modifiers = pattern_modifiers
+
+    @classmethod
+    def from_protocol_name(cls, name):
+        if not isinstance(name, bytes):
+            raise NoiseProtocolNameError('Protocol name has to be of type "bytes" not {}'.format(type(name)))
+        if len(name) > MAX_PROTOCOL_NAME_LEN:
+            raise NoiseProtocolNameError('Protocol name too long, has to be at most '
+                                         '{} chars long'.format(MAX_PROTOCOL_NAME_LEN))
+
+        unpacked = name.decode().split('_')
+        if unpacked[0] != 'Noise':
+            raise NoiseProtocolNameError('Noise Protocol name shall begin with Noise! Provided: {}'.format(name))
+
+        # Extract pattern name and pattern modifiers
+        pattern = ''
+        modifiers_str = None
+        for i, char in enumerate(unpacked[1]):
+            if char.isupper():
+                pattern += char
+            else:
+                # End of pattern, now look for modifiers
+                modifiers_str = unpacked[1][i:]  # Will be empty string if it exceeds string size
+                break
+        modifiers = modifiers_str.split('+') if modifiers_str else []
+
+        return cls(
+            pattern=pattern,
+            dh=unpacked[2],
+            cipher=unpacked[3],
+            hash=unpacked[4],
+            keypair=unpacked[2],
+            pattern_modifiers=modifiers
+        )
diff --git a/noise/patterns.py b/noise/patterns.py
index cca285a..e481f77 100644
--- a/noise/patterns.py
+++ b/noise/patterns.py
@@ -1,85 +1,9 @@
-from typing import List
-
-from .constants import TOKEN_E, TOKEN_S, TOKEN_EE, TOKEN_ES, TOKEN_SE, TOKEN_SS, TOKEN_PSK
-
-
-class Pattern(object):
-    """
-    TODO document
-    """
-    def __init__(self):
-        # As per specification, if both parties have pre-messages, the initiator is listed first. To reduce complexity,
-        # pre_messages shall be a list of two lists:
-        # the first for the initiator's pre-messages, the second for the responder
-        self.pre_messages = [
-            [],
-            []
-        ]
-
-        # List of lists of valid tokens, alternating between tokens for initiator and responder
-        self.tokens = []
-
-        self.name = ''
-        self.one_way = False
-        self.psk_count = 0
-
-    def has_pre_messages(self):
-        return any(map(lambda x: len(x) > 0, self.pre_messages))
-
-    def get_initiator_pre_messages(self) -> list:
-        return self.pre_messages[0].copy()
-
-    def get_responder_pre_messages(self) -> list:
-        return self.pre_messages[1].copy()
-
-    def apply_pattern_modifiers(self, modifiers: List[str]) -> None:
-        # Applies given pattern modifiers to self.tokens of the Pattern instance.
-        for modifier in modifiers:
-            if modifier.startswith('psk'):
-                try:
-                    index = int(modifier.replace('psk', '', 1))
-                except ValueError:
-                    raise ValueError('Improper psk modifier {}'.format(modifier))
-
-                if index // 2 > len(self.tokens):
-                    raise ValueError('Modifier {} cannot be applied - pattern has not enough messages'.format(modifier))
-
-                # Add TOKEN_PSK in the correct place in the correct message
-                if index == 0:  # if 0, insert at the beginning of first message
-                    self.tokens[0].insert(0, TOKEN_PSK)
-                else:  # if bigger than zero, append at the end of first, second etc.
-                    self.tokens[index - 1].append(TOKEN_PSK)
-                self.psk_count += 1
-
-            elif modifier == 'fallback':
-                raise NotImplementedError  # TODO implement
-
-            else:
-                raise ValueError('Unknown pattern modifier {}'.format(modifier))
-
-    def get_required_keypairs(self, initiator: bool) -> list:
-        required = []
-        if initiator:
-            if self.name[0] in ('K', 'X', 'I'):
-                required.append('s')
-            if self.one_way or self.name[1] == 'K':
-                required.append('rs')
-        else:
-            if self.name[0] == 'K':
-                required.append('rs')
-            if self.one_way or self.name[1] in ['K', 'X']:
-                required.append('s')
-        return required
+from noise.constants import TOKEN_S, TOKEN_E, TOKEN_ES, TOKEN_SS, TOKEN_EE, TOKEN_SE
+from noise.functions.patterns import OneWayPattern, Pattern
 
 
 # One-way patterns
 
-class OneWayPattern(Pattern):
-    def __init__(self):
-        super(OneWayPattern, self).__init__()
-        self.one_way = True
-
-
 class PatternN(OneWayPattern):
     def __init__(self):
         super(PatternN, self).__init__()
@@ -281,22 +205,3 @@ class PatternIX(Pattern):
             [TOKEN_E, TOKEN_S],
             [TOKEN_E, TOKEN_EE, TOKEN_SE, TOKEN_S, TOKEN_ES]
         ]
-
-
-patterns_map = {
-    'PatternN': PatternN,
-    'PatternK': PatternK,
-    'PatternX': PatternX,
-    'PatternNN': PatternNN,
-    'PatternKN': PatternKN,
-    'PatternNK': PatternNK,
-    'PatternKK': PatternKK,
-    'PatternNX': PatternNX,
-    'PatternKX': PatternKX,
-    'PatternXN': PatternXN,
-    'PatternIN': PatternIN,
-    'PatternXK': PatternXK,
-    'PatternIK': PatternIK,
-    'PatternXX': PatternXX,
-    'PatternIX': PatternIX,
-}
diff --git a/noise/state.py b/noise/state.py
index 63e53b6..312550f 100644
--- a/noise/state.py
+++ b/noise/state.py
@@ -16,7 +16,7 @@ class CipherState(object):
     def __init__(self, noise_protocol):
         self.k = Empty()
         self.n = None
-        self.cipher = noise_protocol.cipher_fn()
+        self.cipher = noise_protocol.cipher_class()
 
     def initialize_key(self, key):
         """
@@ -363,7 +363,7 @@ class HandshakeState(object):
         for token in message_pattern:
             if token == TOKEN_E:
                 # Sets re to the next DHLEN bytes from the message. Calls MixHash(re.public_key).
-                self.re = self.noise_protocol.keypair_fn.from_public_bytes(bytes(message[:dhlen]))
+                self.re = self.noise_protocol.keypair_class.from_public_bytes(bytes(message[:dhlen]))
                 message = message[dhlen:]
                 self.symmetric_state.mix_hash(self.re.public_bytes)
                 if self.noise_protocol.is_psk_handshake:
@@ -378,7 +378,9 @@ class HandshakeState(object):
                 else:
                     temp = bytes(message[:dhlen])
                     message = message[dhlen:]
-                self.rs = self.noise_protocol.keypair_fn.from_public_bytes(self.symmetric_state.decrypt_and_hash(temp))
+                self.rs = self.noise_protocol.keypair_class.from_public_bytes(
+                    self.symmetric_state.decrypt_and_hash(temp)
+                )
 
             elif token == TOKEN_EE:
                 # Calls MixKey(DH(e, re)).
diff --git a/requirements.txt b/requirements.txt
index 20fa3b5..34d60e5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1 +1 @@
-cryptography==2.1.4
+cryptography>=2.5
diff --git a/setup.py b/setup.py
index 0187754..964f35d 100644
--- a/setup.py
+++ b/setup.py
@@ -13,7 +13,7 @@ except (IOError, ImportError):
 
 setup(
     name='noiseprotocol',
-    version='0.2.2',
+    version='0.3.0',
     description='Implementation of Noise Protocol Framework',
     long_description=long_description,
     url='https://github.com/plizonczyk/noiseprotocol',
@@ -35,6 +35,6 @@ setup(
     ],
     keywords='cryptography noiseprotocol noise security',
     packages=find_packages(exclude=['contrib', 'docs', 'tests', 'examples']),
-    install_requires=['cryptography>=2.1.4'],
+    install_requires=['cryptography>=2.5'],
     python_requires='~=3.5',  # we like 3.5, 3.6, and beyond, but not 4.0
 )
diff --git a/tests/test_rev33_compat.py b/tests/test_rev33_compat.py
index 13eeb21..ec070c8 100644
--- a/tests/test_rev33_compat.py
+++ b/tests/test_rev33_compat.py
@@ -1,3 +1,4 @@
+from noise.backends.default import noise_backend
 from noise.noise_protocol import NoiseProtocol
 from noise.state import CipherState, SymmetricState
 
@@ -8,12 +9,14 @@ class TestRevision33Compatibility(object):
             fn = None
 
         noise_name = b"Noise_NN_25519_AESGCM_SHA3/256"
+
+        modified_backend = noise_backend
+        modified_backend.hashes['SHA3/256'] = FakeSHA3_256  # Add callable to hash functions mapping
         modified_class = NoiseProtocol
-        modified_class.methods['hash']['SHA3/256'] = FakeSHA3_256  # Add callable to hash functions mapping
-        modified_class(noise_name)
+        modified_class(noise_name, modified_backend)
 
     def test_cipher_state_set_nonce(self):
-        noise_protocol = NoiseProtocol(b"Noise_NN_25519_AESGCM_SHA256")
+        noise_protocol = NoiseProtocol(b"Noise_NN_25519_AESGCM_SHA256", backend=noise_backend)
         cipher_state = CipherState(noise_protocol)
         cipher_state.initialize_key(b'\x00'*32)
         assert cipher_state.n == 0