diff --git a/.travis.yml b/.travis.yml
index df43175c3..c47988be8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,7 +23,7 @@ before_install:
   - if [ -n "$SOLC_VERSION" ]; then sudo apt-get install -y tree unzip; fi
 install:
   - if [ -n "$SOLC_VERSION" ]; then /.$TRAVIS_BUILD_DIR/.travis/install_solc.sh; fi
-  - travis_retry pip install setuptools --upgrade
+  - travis_retry pip install pip setuptools --upgrade
   - travis_retry pip install tox
   - travis_retry pip install coverage
   - travis_retry pip install flake8
diff --git a/README.md b/README.md
index 037bbe8a2..15091d989 100644
--- a/README.md
+++ b/README.md
@@ -160,7 +160,7 @@ Contains the Transaction class, with the following methods and values:
 
 ### ethereum.tools.keys
 
-Creates encrypted private key storaes
+Creates encrypted private key storages
 
 * `decode_keystore_json(jsondata, password)` - returns the private key from an encrypted keystore object. NOTE: if you are loading from a file, the most convenient way to do this is `import json; key = decode_keystore_json(json.load(open('filename.json')), 'password')`
 * `make_keystore_json(key, pw, kdf='pbkdf2', cipher='aes-128-ctr')` - creates an encrypted keystore object for the key. Keeping `kdf` and `cipher` at their default values is recommended.
diff --git a/dev_requirements.txt b/dev_requirements.txt
index 8bd463833..5d6a78a0d 100644
--- a/dev_requirements.txt
+++ b/dev_requirements.txt
@@ -3,4 +3,5 @@ coveralls
 pytest>=2.9.0
 pytest-catchlog==1.2.2
 pytest-timeout==1.0.0
+py-ecc
 https://github.com/ethereum/serpent/tarball/develop
diff --git a/ethereum/pow/chain.py b/ethereum/pow/chain.py
index 5db89f281..6afb2eb3a 100644
--- a/ethereum/pow/chain.py
+++ b/ethereum/pow/chain.py
@@ -365,8 +365,8 @@ def add_block(self, block):
         self.add_child(block)
         self.db.put('head_hash', self.head_hash)
         self.db.put(block.hash, rlp.encode(block))
-        self.db.put(b'changed:'+block.hash, b''.join(list(changed.keys())))
-        log.debug('Saved %d address change logs' % len(changed.keys()))
+        self.db.put(b'changed:'+block.hash, b''.join([k.encode() if isinstance(k, str) else k for k in list(changed.keys())]))
+        print('Saved %d address change logs' % len(changed.keys()))
         self.db.put(b'deletes:'+block.hash, b''.join(deletes))
         log.debug('Saved %d trie node deletes for block %d (%s)' % (len(deletes), block.number, utils.encode_hex(block.hash)))
         # Delete old junk data
diff --git a/ethereum/tools/_solidity.py b/ethereum/tools/_solidity.py
index 8eb47f055..b1b1d979c 100644
--- a/ethereum/tools/_solidity.py
+++ b/ethereum/tools/_solidity.py
@@ -165,6 +165,13 @@ def solidity_names(code):  # pylint: disable=too-many-branches
                 if result:
                     names.append(('contract', result.groups()[0]))
 
+            if char == 'i' and code[pos: pos + 9] == 'interface':
+                result = re.match('^interface[^_$a-zA-Z]+([_$a-zA-Z][_$a-zA-Z0-9]*)', code[pos:])
+
+                if result:
+                    names.append(('contract', result.groups()[0]))
+
+
             if char == 'l' and code[pos: pos + 7] == 'library':
                 result = re.match('^library[^_$a-zA-Z]+([_$a-zA-Z][_$a-zA-Z0-9]*)', code[pos:])
 
diff --git a/ethereum/tools/keys.py b/ethereum/tools/keys.py
index d9b46232a..e9520c0f5 100644
--- a/ethereum/tools/keys.py
+++ b/ethereum/tools/keys.py
@@ -1,6 +1,6 @@
 import os
-import pbkdf2
 import sys
+from hashlib import pbkdf2_hmac
 
 from rlp.utils import decode_hex
 from ethereum.utils import encode_hex
@@ -43,9 +43,8 @@
 }
 
 PBKDF2_CONSTANTS = {
-    "prf": "hmac-sha256",
     "dklen": 32,
-    "c": 262144
+    "rounds": 262144
 }
 
 
@@ -96,9 +95,8 @@ def mk_pbkdf2_params():
 
 
 def pbkdf2_hash(val, params):
-    assert params["prf"] == "hmac-sha256"
-    return pbkdf2.PBKDF2(val, decode_hex(params["salt"]), params["c"],
-                         SHA256).read(params["dklen"])
+    return pbkdf2_hmac('sha256', val, decode_hex(params["salt"]),
+                       params["rounds"], params["dklen"])
 
 
 kdfs = {
diff --git a/ethereum/tools/tester.py b/ethereum/tools/tester.py
index 8edea6c37..02791a43e 100644
--- a/ethereum/tools/tester.py
+++ b/ethereum/tools/tester.py
@@ -157,7 +157,7 @@ def __init__(self, alloc=base_alloc, env=None, genesis=None):
 
     def direct_tx(self, transaction):
         self.last_tx = transaction
-        if self.last_sender and privtoaddr(self.last_sender) != transaction.sender:
+        if self.last_sender is not None and privtoaddr(self.last_sender) != transaction.sender:
             self.last_sender = None
         success, output = apply_transaction(self.head_state, transaction)
         self.block.transactions.append(transaction)
diff --git a/ethereum/utils.py b/ethereum/utils.py
index c54e4dd52..e82ab0c53 100644
--- a/ethereum/utils.py
+++ b/ethereum/utils.py
@@ -13,11 +13,11 @@
 
 
 try:
-    import secp256k1
+    import coincurve
 except ImportError:
     import warnings
-    warnings.warn('could not import secp256k1', ImportWarning)
-    secp256k1 = None
+    warnings.warn('could not import coincurve', ImportWarning)
+    coincurve = None
 
 big_endian_to_int = lambda x: big_endian_int.deserialize(str_to_bytes(x).lstrip(b'\x00'))
 int_to_big_endian = lambda x: big_endian_int.serialize(x)
@@ -85,22 +85,15 @@ def bytes_to_int(value):
 
 
 def ecrecover_to_pub(rawhash, v, r, s):
-    if secp256k1 and hasattr(secp256k1, "PublicKey"):
-        # Legendre symbol check; the secp256k1 library does not seem to do this
-        pk = secp256k1.PublicKey(flags=secp256k1.ALL_FLAGS)
-        xc = r * r * r + 7
-        assert pow(xc, (SECP256K1P - 1) // 2, SECP256K1P) == 1
+    if coincurve and hasattr(coincurve, "PublicKey"):
         try:
-            pk.public_key = pk.ecdsa_recover(
+            pk = coincurve.PublicKey.from_signature_and_message(
+                zpad(utils.bytearray_to_bytestr(int_to_32bytearray(r)), 32) + zpad(utils.bytearray_to_bytestr(int_to_32bytearray(s)), 32) +
+                utils.ascii_chr(v - 27),
                 rawhash,
-                pk.ecdsa_recoverable_deserialize(
-                    zpad(bytearray_to_bytestr(int_to_32bytearray(r)), 32) +
-                    zpad(bytearray_to_bytestr(int_to_32bytearray(s)), 32),
-                    v - 27
-                ),
-                raw=True
+                hasher=None,
             )
-            pub = pk.serialize(compressed=False)[1:]
+            pub = pk.format(compressed=False)[1:]
         except:
             pub = b"\x00" * 64
     else:
@@ -111,12 +104,9 @@ def ecrecover_to_pub(rawhash, v, r, s):
 
 
 def ecsign(rawhash, key):
-    if secp256k1 and hasattr(secp256k1, 'PrivateKey'):
-        pk = secp256k1.PrivateKey(key, raw=True)
-        signature = pk.ecdsa_recoverable_serialize(
-            pk.ecdsa_sign_recoverable(rawhash, raw=True)
-        )
-        signature = signature[0] + bytearray_to_bytestr([signature[1]])
+    if coincurve and hasattr(coincurve, 'PrivateKey'):
+        pk = coincurve.PrivateKey(key)
+        signature = pk.sign_recoverable(msghash, hasher=None)
         v = safe_ord(signature[64]) + 27
         r = big_endian_to_int(signature[0:32])
         s = big_endian_to_int(signature[32:64])
diff --git a/requirements.txt b/requirements.txt
index 5c22c1798..539243791 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,8 +1,9 @@
 pysha3>=1.0.1
 PyYAML
 repoze.lru
-pbkdf2
 scrypt
 py_ecc
 rlp>=0.4.7
 https://github.com/ethereum/ethash/tarball/master
+pycryptodome==3.4.6
+coincurve>=5.0.1
diff --git a/setup.py b/setup.py
index 2c07d55a9..c2b1c6220 100644
--- a/setup.py
+++ b/setup.py
@@ -41,7 +41,7 @@
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
     ],
 )