From b8d70f34d349a3b4c05bd3d43754826bc9718e7f Mon Sep 17 00:00:00 2001
From: diminator <dimi.dejonghe@gmail.com>
Date: Tue, 21 Mar 2017 15:26:57 +0100
Subject: [PATCH] keypair from secret

---
 bigchaindb/common/crypto.py | 48 ++++++++++++++++++++++++++++++++++---
 tests/common/test_crypto.py | 13 ++++++++++
 2 files changed, 58 insertions(+), 3 deletions(-)
 create mode 100644 tests/common/test_crypto.py

diff --git a/bigchaindb/common/crypto.py b/bigchaindb/common/crypto.py
index 99663fe9..9bced92a 100644
--- a/bigchaindb/common/crypto.py
+++ b/bigchaindb/common/crypto.py
@@ -1,10 +1,10 @@
 # Separate all crypto code so that we can easily test several implementations
 from collections import namedtuple
 
+import nacl.signing
 import sha3
 from cryptoconditions import crypto
 
-
 CryptoKeypair = namedtuple('CryptoKeypair', ('private_key', 'public_key'))
 
 
@@ -13,8 +13,46 @@ def hash_data(data):
     return sha3.sha3_256(data.encode()).hexdigest()
 
 
-def generate_key_pair():
+class Ed25519SigningKeyFromHash(crypto.Ed25519SigningKey):
+
+    def __init__(self, key, encoding='base58'):
+        super().__init__(key, encoding=encoding)
+
+    @classmethod
+    def generate(cls, hash_bytes):
+        return cls(nacl.signing.SigningKey(hash_bytes).encode(encoder=crypto.Base58Encoder))
+
+
+def ed25519_generate_key_pair_from_secret(secret):
+    """
+    Generate a new key pair.
+
+    Args:
+        secret (:class:`string`): A secret that serves as a seed
+
+    Returns:
+        A tuple of (private_key, public_key) encoded in base58.
+    """
+
+    # if you want to do this correctly, use a key derivation function!
+    if not isinstance(secret, bytes):
+        secret = secret.encode()
+
+    hash_bytes = sha3.keccak_256(secret).digest()
+    sk = Ed25519SigningKeyFromHash.generate(hash_bytes=hash_bytes)
+    # Private key
+    private_value_base58 = sk.encode(encoding='base58')
+
+    # Public key
+    public_value_compressed_base58 = sk.get_verifying_key().encode(encoding='base58')
+
+    return private_value_base58, public_value_compressed_base58
+
+
+def generate_key_pair(secret=None):
     """Generates a cryptographic key pair.
+    Args:
+        secret (:class:`string`): A secret that serves as a seed
 
     Returns:
         :class:`~bigchaindb.common.crypto.CryptoKeypair`: A
@@ -23,9 +61,13 @@ def generate_key_pair():
         :attr:`~bigchaindb.common.crypto.CryptoKeypair.public_key`.
 
     """
+    if secret:
+        keypair_raw = ed25519_generate_key_pair_from_secret(secret)
+    else:
+        keypair_raw = crypto.ed25519_generate_key_pair()
     # TODO FOR CC: Adjust interface so that this function becomes unnecessary
     return CryptoKeypair(
-        *(k.decode() for k in crypto.ed25519_generate_key_pair()))
+        *(k.decode() for k in keypair_raw))
 
 
 PrivateKey = crypto.Ed25519SigningKey
diff --git a/tests/common/test_crypto.py b/tests/common/test_crypto.py
new file mode 100644
index 00000000..a594e3b8
--- /dev/null
+++ b/tests/common/test_crypto.py
@@ -0,0 +1,13 @@
+
+
+def test_crypto_keypair():
+    from bigchaindb.common.crypto import generate_key_pair
+
+    secret = 'much secret'
+    keypair = generate_key_pair(secret=secret)
+
+    assert len(keypair.public_key) == len(generate_key_pair().public_key)
+    # TODO: 43 !== 44 -> need to check why
+    # assert len(keypair.private_key) == len(generate_key_pair().private_key)
+    assert keypair.public_key == generate_key_pair(secret).public_key
+    assert keypair.private_key == generate_key_pair(secret).private_key