diff --git a/libdevcrypto/AES.cpp b/libdevcrypto/AES.cpp
index 0682adea3..bcfbbbdc0 100644
--- a/libdevcrypto/AES.cpp
+++ b/libdevcrypto/AES.cpp
@@ -34,7 +34,7 @@ struct aes::Aes128Ctr
 	{
 		mode.SetKeyWithIV(_k.data(), sizeof(h128), Nonce::get().data());
 	}
-	CryptoPP::CTR_Mode<CryptoPP::AES>::Encryption mode;
+	CTR_Mode<AES>::Encryption mode;
 };
 
 Stream::Stream(StreamType _t, h128 _ckey):
diff --git a/libdevcrypto/AES.h b/libdevcrypto/AES.h
index 7a1beefe5..af4f781cd 100644
--- a/libdevcrypto/AES.h
+++ b/libdevcrypto/AES.h
@@ -53,6 +53,9 @@ public:
 	virtual size_t streamOut(bytes& o_bytes);
 	
 private:
+	Stream(Stream const&) = delete;
+	Stream& operator=(Stream const&) = delete;
+	
 	h128 m_cSecret;
 	bytes m_text;
 
@@ -74,6 +77,9 @@ public:
 	void adjustInterval(unsigned _interval) { m_macInterval = _interval; };
 	
 private:
+	AuthenticatedStream(AuthenticatedStream const&) = delete;
+	AuthenticatedStream& operator=(AuthenticatedStream const&) = delete;
+	
 	std::atomic<unsigned> m_macInterval;
 	h128 m_macSecret;
 };
diff --git a/libdevcrypto/Common.cpp b/libdevcrypto/Common.cpp
index 9107fe9ca..fa5a544a1 100644
--- a/libdevcrypto/Common.cpp
+++ b/libdevcrypto/Common.cpp
@@ -33,33 +33,33 @@ using namespace dev::crypto;
 
 static Secp256k1 s_secp256k1;
 
-Public dev::toPublic(Secret _secret)
+Public dev::toPublic(Secret const& _secret)
 {
 	Public p;
 	s_secp256k1.toPublic(_secret, p);
 	return std::move(p);
 }
 
-Address dev::toAddress(Public _public)
+Address dev::toAddress(Public const& _public)
 {
 	return s_secp256k1.toAddress(_public);
 }
 
-Address dev::toAddress(Secret _secret)
+Address dev::toAddress(Secret const& _secret)
 {
 	Public p;
 	s_secp256k1.toPublic(_secret, p);
 	return s_secp256k1.toAddress(p);
 }
 
-void dev::encrypt(Public _k, bytesConstRef _plain, bytes& o_cipher)
+void dev::encrypt(Public const& _k, bytesConstRef _plain, bytes& o_cipher)
 {
 	bytes io = _plain.toBytes();
 	s_secp256k1.encrypt(_k, io);
 	o_cipher = std::move(io);
 }
 
-bool dev::decrypt(Secret _k, bytesConstRef _cipher, bytes& o_plaintext)
+bool dev::decrypt(Secret const& _k, bytesConstRef _cipher, bytes& o_plaintext)
 {
 	bytes io = _cipher.toBytes();
 	s_secp256k1.decrypt(_k, io);
@@ -69,19 +69,19 @@ bool dev::decrypt(Secret _k, bytesConstRef _cipher, bytes& o_plaintext)
 	return true;
 }
 
-Public dev::recover(Signature _sig, h256 _message)
+Public dev::recover(Signature const& _sig, h256 const& _message)
 {
 	return s_secp256k1.recover(_sig, _message.ref());
 }
 
-Signature dev::sign(Secret _k, h256 _hash)
+Signature dev::sign(Secret const& _k, h256 const& _hash)
 {
 	return s_secp256k1.sign(_k, _hash);
 }
 
-bool dev::verify(Public _p, Signature _s, h256 _hash)
+bool dev::verify(Public const& _p, Signature const& _s, h256 const& _hash)
 {
-	return s_secp256k1.verify(_p, _s, bytesConstRef(_hash.data(), 32), true);
+	return s_secp256k1.verify(_p, _s, _hash.ref(), true);
 }
 
 KeyPair KeyPair::create()
@@ -91,11 +91,7 @@ KeyPair KeyPair::create()
 
 	for (int i = 0; i < 100; ++i)
 	{
-		h256 sec;
-		for (unsigned i = 0; i < 32; ++i)
-			sec[i] = (byte)d(s_eng);
-
-		KeyPair ret(sec);
+		KeyPair ret(FixedHash<32>::random(s_eng));
 		if (ret.address())
 			return ret;
 	}
@@ -144,7 +140,7 @@ h256 Nonce::get(bool _commit)
 		else
 		{
 			// todo: replace w/entropy from user and system
-			std::mt19937_64 s_eng(time(0));
+			std::mt19937_64 s_eng(time(0) + chrono::high_resolution_clock::now().time_since_epoch().count());
 			std::uniform_int_distribution<uint16_t> d(0, 255);
 			for (unsigned i = 0; i < 32; ++i)
 				s_seed[i] = (byte)d(s_eng);
diff --git a/libdevcrypto/Common.h b/libdevcrypto/Common.h
index cd0996826..87d47937e 100644
--- a/libdevcrypto/Common.h
+++ b/libdevcrypto/Common.h
@@ -30,7 +30,7 @@
 
 namespace dev
 {
-	
+
 /// A secret key: 32 bytes.
 /// @NOTE This is not endian-specific; it's just a bunch of bytes.
 using Secret = h256;
@@ -59,29 +59,29 @@ using AddressSet = std::set<h160>;
 using Secrets = h256s;
 
 /// Convert a secret key into the public key equivalent.
-Public toPublic(Secret _secret);
+Public toPublic(Secret const& _secret);
 
 /// Convert a public key to address.
-Address toAddress(Public _public);
+Address toAddress(Public const& _public);
 
 /// Convert a secret key into address of public key equivalent.
 /// @returns 0 if it's not a valid secret key.
-Address toAddress(Secret _secret);
+Address toAddress(Secret const& _secret);
 
 /// Encrypts plain text using Public key.
-void encrypt(Public _k, bytesConstRef _plain, bytes& o_cipher);
+void encrypt(Public const& _k, bytesConstRef _plain, bytes& o_cipher);
 
 /// Decrypts cipher using Secret key.
-bool decrypt(Secret _k, bytesConstRef _cipher, bytes& o_plaintext);
+bool decrypt(Secret const& _k, bytesConstRef _cipher, bytes& o_plaintext);
 	
 /// Recovers Public key from signed message hash.
-Public recover(Signature _sig, h256 _hash);
+Public recover(Signature const& _sig, h256 const& _hash);
 	
 /// Returns siganture of message hash.
-Signature sign(Secret _k, h256 _hash);
+Signature sign(Secret const& _k, h256 const& _hash);
 	
 /// Verify signature.
-bool verify(Public _k, Signature _s, h256 _hash);
+bool verify(Public const& _k, Signature const& _s, h256 const& _hash);
 
 /// Simple class that represents a "key pair".
 /// All of the data of the class can be regenerated from the secret key (m_secret) alone.