diff --git a/src/Makefile.am b/src/Makefile.am
index d0fe3d0d8..fc3567e1b 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,639 +1,640 @@
 # Copyright (c) 2013-2016 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 DIST_SUBDIRS = secp256k1 univalue
 
 AM_LDFLAGS = $(PTHREAD_CFLAGS) $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(SANITIZER_LDFLAGS)
 AM_CXXFLAGS = $(HARDENED_CXXFLAGS) $(ERROR_CXXFLAGS) $(SANITIZER_CXXFLAGS)
 AM_CPPFLAGS = $(HARDENED_CPPFLAGS)
 EXTRA_LIBRARIES =
 
 if EMBEDDED_UNIVALUE
 LIBUNIVALUE = univalue/libunivalue.la
 
 $(LIBUNIVALUE): $(wildcard univalue/lib/*) $(wildcard univalue/include/*)
 	$(AM_V_at)$(MAKE) $(AM_MAKEFLAGS) -C $(@D) $(@F)
 else
 LIBUNIVALUE = $(UNIVALUE_LIBS)
 endif
 
 BITCOIN_INCLUDES=-I$(builddir) -I$(builddir)/obj $(BDB_CPPFLAGS) $(BOOST_CPPFLAGS) $(LEVELDB_CPPFLAGS) $(CRYPTO_CFLAGS) $(SSL_CFLAGS)
 
 BITCOIN_INCLUDES += -I$(srcdir)/secp256k1/include
 BITCOIN_INCLUDES += $(UNIVALUE_CFLAGS)
 
 BITCOIN_SEEDER_INCLUDES = -I$(srcdir)/seeder
 BITCOIN_SEEDER_INCLUDES += $(BITCOIN_INCLUDES)
 
 LIBBITCOIN_SERVER=libbitcoin_server.a
 LIBBITCOIN_COMMON=libbitcoin_common.a
 LIBBITCOIN_CONSENSUS=libbitcoin_consensus.a
 LIBBITCOIN_CLI=libbitcoin_cli.a
 LIBBITCOIN_UTIL=libbitcoin_util.a
 LIBBITCOIN_CRYPTO_BASE=crypto/libbitcoin_crypto_base.a
 LIBBITCOINQT=qt/libbitcoinqt.a
 LIBSECP256K1=secp256k1/libsecp256k1.la
 
 if ENABLE_ZMQ
 LIBBITCOIN_ZMQ=libbitcoin_zmq.a
 endif
 if BUILD_BITCOIN_LIBS
 LIBBITCOINCONSENSUS=libbitcoinconsensus.la
 endif
 if BUILD_BITCOIN_SEEDER
 LIBBITCOIN_SEEDER=libbitcoin_seeder.a
 endif
 if ENABLE_WALLET
 LIBBITCOIN_WALLET=libbitcoin_wallet.a
 endif
 
 LIBBITCOIN_CRYPTO= $(LIBBITCOIN_CRYPTO_BASE)
 if ENABLE_SSE41
 LIBBITCOIN_CRYPTO_SSE41 = crypto/libbitcoin_crypto_sse41.a
 LIBBITCOIN_CRYPTO += $(LIBBITCOIN_CRYPTO_SSE41)
 endif
 if ENABLE_AVX2
 LIBBITCOIN_CRYPTO_AVX2 = crypto/libbitcoin_crypto_avx2.a
 LIBBITCOIN_CRYPTO += $(LIBBITCOIN_CRYPTO_AVX2)
 endif
 if ENABLE_SHANI
 LIBBITCOIN_CRYPTO_SHANI = crypto/libbitcoin_crypto_shani.a
 LIBBITCOIN_CRYPTO += $(LIBBITCOIN_CRYPTO_SHANI)
 endif
 
 $(LIBSECP256K1): $(wildcard secp256k1/src/*) $(wildcard secp256k1/include/*)
 	$(AM_V_at)$(MAKE) $(AM_MAKEFLAGS) -C $(@D) $(@F)
 
 # Make is not made aware of per-object dependencies to avoid limiting building parallelization
 # But to build the less dependent modules first, we manually select their order here:
 EXTRA_LIBRARIES += \
   $(LIBBITCOIN_CRYPTO) \
   $(LIBBITCOIN_UTIL) \
   $(LIBBITCOIN_COMMON) \
   $(LIBBITCOIN_CONSENSUS) \
   $(LIBBITCOIN_SERVER) \
   $(LIBBITCOIN_CLI) \
   $(LIBBITCOIN_SEEDER) \
   $(LIBBITCOIN_WALLET) \
   $(LIBBITCOIN_ZMQ)
 
 lib_LTLIBRARIES = $(LIBBITCOINCONSENSUS)
 
 bin_PROGRAMS =
 noinst_PROGRAMS =
 TESTS =
 BENCHMARKS =
 
 if BUILD_BITCOIND
   bin_PROGRAMS += bitcoind
 endif
 
 if BUILD_BITCOIN_SEEDER
   bin_PROGRAMS += bitcoin-seeder
 endif
 
 if BUILD_BITCOIN_UTILS
   bin_PROGRAMS += bitcoin-cli bitcoin-tx
 endif
 
 .PHONY: FORCE check-symbols check-security
 # bitcoin core #
 BITCOIN_CORE_H = \
   addrdb.h \
   addrman.h \
+  avalanche_impl.h \
   base58.h \
   bloom.h \
   blockencodings.h \
   blockfileinfo.h \
   blockindexworkcomparator.h \
   blockstatus.h \
   blockvalidity.h \
   cashaddr.h \
   cashaddrenc.h \
   chain.h \
   chainparams.h \
   chainparamsbase.h \
   chainparamsseeds.h \
   checkpoints.h \
   checkqueue.h \
   clientversion.h \
   coins.h \
   compat.h \
   compat/byteswap.h \
   compat/endian.h \
   compat/sanity.h \
   compressor.h \
   config.h \
   consensus/activation.h \
   consensus/consensus.h \
   consensus/tx_verify.h \
   core_io.h \
   core_memusage.h \
   cuckoocache.h \
   diskblockpos.h \
   dstencode.h \
   fs.h \
   globals.h \
   httprpc.h \
   httpserver.h \
   indirectmap.h \
   init.h \
   key.h \
   keystore.h \
   dbwrapper.h \
   limitedmap.h \
   logging.h \
   memusage.h \
   merkleblock.h \
   miner.h \
   net.h \
   net_processing.h \
   netaddress.h \
   netbase.h \
   netmessagemaker.h \
   noui.h \
   policy/fees.h \
   policy/policy.h \
   pow.h \
   protocol.h \
   random.h \
   reverselock.h \
   rpc/blockchain.h \
   rpc/client.h \
   rpc/jsonrpcrequest.h \
   rpc/mining.h \
   rpc/misc.h \
   rpc/protocol.h \
   rpc/safemode.h \
   rpc/server.h \
   rpc/tojson.h \
   rpc/register.h \
   rwcollection.h \
   scheduler.h \
   script/scriptcache.h \
   script/sigcache.h \
   script/sign.h \
   script/standard.h \
   script/ismine.h \
   streams.h \
   support/allocators/secure.h \
   support/allocators/zeroafterfree.h \
   support/cleanse.h \
   support/events.h \
   support/lockedpool.h \
   sync.h \
   threadsafety.h \
   threadinterrupt.h \
   timedata.h \
   torcontrol.h \
   txdb.h \
   txmempool.h \
   ui_interface.h \
   undo.h \
   util.h \
   utilmoneystr.h \
   utiltime.h \
   validation.h \
   validationinterface.h \
   versionbits.h \
   wallet/coincontrol.h \
   wallet/crypter.h \
   wallet/db.h \
   wallet/finaltx.h \
   wallet/rpcdump.h \
   wallet/fees.h \
   wallet/init.h \
   wallet/rpcwallet.h \
   wallet/wallet.h \
   wallet/walletdb.h \
   warnings.h \
   zmq/zmqabstractnotifier.h \
   zmq/zmqconfig.h\
   zmq/zmqnotificationinterface.h \
   zmq/zmqpublishnotifier.h
 
 
 obj/build.h: FORCE
 	@$(MKDIR_P) "$(builddir)/obj"
 	@$(top_srcdir)/share/genbuild.sh "$(abs_top_builddir)/src/obj/build.h" \
 	  "$(abs_top_srcdir)"
 libbitcoin_util_a-clientversion.$(OBJEXT): obj/build.h
 
 # server: shared between bitcoind and bitcoin-qt
 libbitcoin_server_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(MINIUPNPC_CPPFLAGS) $(EVENT_CFLAGS) $(EVENT_PTHREADS_CFLAGS)
 libbitcoin_server_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_server_a_SOURCES = \
   addrman.cpp \
   addrdb.cpp \
   bloom.cpp \
   blockencodings.cpp \
   chain.cpp \
   checkpoints.cpp \
   config.cpp \
   consensus/activation.cpp \
   consensus/tx_verify.cpp \
   globals.cpp \
   httprpc.cpp \
   httpserver.cpp \
   init.cpp \
   dbwrapper.cpp \
   merkleblock.cpp \
   miner.cpp \
   net.cpp \
   net_processing.cpp \
   noui.cpp \
   policy/fees.cpp \
   policy/policy.cpp \
   pow.cpp \
   rest.cpp \
   rpc/abc.cpp \
   rpc/blockchain.cpp \
   rpc/jsonrpcrequest.cpp \
   rpc/mining.cpp \
   rpc/misc.cpp \
   rpc/net.cpp \
   rpc/rawtransaction.cpp \
   rpc/safemode.cpp \
   rpc/server.cpp \
   script/scriptcache.cpp \
   script/sigcache.cpp \
   script/ismine.cpp \
   timedata.cpp \
   torcontrol.cpp \
   txdb.cpp \
   txmempool.cpp \
   ui_interface.cpp \
   validation.cpp \
   validationinterface.cpp \
   versionbits.cpp \
   $(BITCOIN_CORE_H)
 
 if ENABLE_ZMQ
 libbitcoin_zmq_a_CPPFLAGS = $(BITCOIN_INCLUDES) $(ZMQ_CFLAGS)
 libbitcoin_zmq_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_zmq_a_SOURCES = \
   zmq/zmqabstractnotifier.cpp \
   zmq/zmqnotificationinterface.cpp \
   zmq/zmqpublishnotifier.cpp
 endif
 
 
 # wallet: shared between bitcoind and bitcoin-qt, but only linked
 # when wallet enabled
 libbitcoin_wallet_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libbitcoin_wallet_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_wallet_a_SOURCES = \
   wallet/crypter.cpp \
   wallet/db.cpp \
   wallet/finaltx.cpp \
   wallet/fees.cpp \
   wallet/init.cpp \
   wallet/rpcdump.cpp \
   wallet/rpcwallet.cpp \
   wallet/wallet.cpp \
   wallet/walletdb.cpp \
   $(BITCOIN_CORE_H)
 
 # crypto primitives library
 crypto_libbitcoin_crypto_base_a_CPPFLAGS = $(AM_CPPFLAGS)
 crypto_libbitcoin_crypto_base_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 crypto_libbitcoin_crypto_base_a_SOURCES = \
   crypto/aes.cpp \
   crypto/aes.h \
   crypto/chacha20.h \
   crypto/chacha20.cpp \
   crypto/common.h \
   crypto/hmac_sha256.cpp \
   crypto/hmac_sha256.h \
   crypto/hmac_sha512.cpp \
   crypto/hmac_sha512.h \
   crypto/ripemd160.cpp \
   crypto/ripemd160.h \
   crypto/sha1.cpp \
   crypto/sha1.h \
   crypto/sha256.cpp \
   crypto/sha256.h \
   crypto/sha512.cpp \
   crypto/sha512.h
 
 if USE_ASM
 crypto_libbitcoin_crypto_base_a_SOURCES += crypto/sha256_sse4.cpp
 endif
 
 crypto_libbitcoin_crypto_sse41_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 crypto_libbitcoin_crypto_sse41_a_CPPFLAGS = $(AM_CPPFLAGS)
 crypto_libbitcoin_crypto_sse41_a_CXXFLAGS += $(SSE41_CXXFLAGS)
 crypto_libbitcoin_crypto_sse41_a_CPPFLAGS += -DENABLE_SSE41
 crypto_libbitcoin_crypto_sse41_a_SOURCES = crypto/sha256_sse41.cpp
 
 crypto_libbitcoin_crypto_avx2_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 crypto_libbitcoin_crypto_avx2_a_CPPFLAGS = $(AM_CPPFLAGS)
 crypto_libbitcoin_crypto_avx2_a_CXXFLAGS += $(AVX2_CXXFLAGS)
 crypto_libbitcoin_crypto_avx2_a_CPPFLAGS += -DENABLE_AVX2
 crypto_libbitcoin_crypto_avx2_a_SOURCES = crypto/sha256_avx2.cpp
 
 crypto_libbitcoin_crypto_shani_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 crypto_libbitcoin_crypto_shani_a_CPPFLAGS = $(AM_CPPFLAGS)
 crypto_libbitcoin_crypto_shani_a_CXXFLAGS += $(SHANI_CXXFLAGS)
 crypto_libbitcoin_crypto_shani_a_CPPFLAGS += -DENABLE_SHANI
 crypto_libbitcoin_crypto_shani_a_SOURCES = crypto/sha256_shani.cpp
 
 # consensus: shared between all executables that validate any consensus rules.
 libbitcoin_consensus_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libbitcoin_consensus_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_consensus_a_SOURCES = \
   amount.h \
   arith_uint256.cpp \
   arith_uint256.h \
   consensus/merkle.cpp \
   consensus/merkle.h \
   consensus/params.h \
   consensus/validation.h \
   feerate.h \
   hash.cpp \
   hash.h \
   prevector.h \
   primitives/block.cpp \
   primitives/block.h \
   primitives/transaction.cpp \
   primitives/transaction.h \
   primitives/txid.h \
   pubkey.cpp \
   pubkey.h \
   script/bitcoinconsensus.cpp \
   script/sighashtype.h \
   script/interpreter.cpp \
   script/interpreter.h \
   script/script.cpp \
   script/script.h \
   script/script_error.cpp \
   script/script_error.h \
   script/script_flags.h \
   script/sigencoding.cpp \
   script/sigencoding.h \
   serialize.h \
   tinyformat.h \
   uint256.cpp \
   uint256.h \
   utilstrencodings.cpp \
   utilstrencodings.h \
   version.h
 
 # common: shared between bitcoind, and bitcoin-qt and non-server tools
 libbitcoin_common_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libbitcoin_common_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_common_a_SOURCES = \
   amount.cpp \
   base58.cpp \
   cashaddr.cpp \
   cashaddrenc.cpp \
   chainparams.cpp \
   config.cpp \
   coins.cpp \
   compressor.cpp \
   dstencode.cpp \
   feerate.cpp \
   globals.cpp \
   core_read.cpp \
   core_write.cpp \
   key.cpp \
   keystore.cpp \
   netaddress.cpp \
   netbase.cpp \
   protocol.cpp \
   scheduler.cpp \
   script/sign.cpp \
   script/standard.cpp \
   warnings.cpp \
   $(BITCOIN_CORE_H)
 
 # util: shared between all executables.
 # This library *must* be included to make sure that the glibc
 # backward-compatibility objects and their sanity checks are linked.
 libbitcoin_util_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libbitcoin_util_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_util_a_SOURCES = \
   support/lockedpool.cpp \
   chainparamsbase.cpp \
   clientversion.cpp \
   compat/glibc_sanity.cpp \
   compat/glibcxx_sanity.cpp \
   compat/strnlen.cpp \
   fs.cpp \
   logging.cpp \
   random.cpp \
   rpc/protocol.cpp \
   support/cleanse.cpp \
   sync.cpp \
   threadinterrupt.cpp \
   uint256.cpp \
   uint256.h \
   util.cpp \
   utilmoneystr.cpp \
   utilstrencodings.cpp \
   utiltime.cpp \
   $(BITCOIN_CORE_H)
 
 if GLIBC_BACK_COMPAT
 libbitcoin_util_a_SOURCES += compat/glibc_compat.cpp
 AM_LDFLAGS += $(COMPAT_LDFLAGS)
 endif
 
 # cli: shared between bitcoin-cli and bitcoin-qt
 libbitcoin_cli_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libbitcoin_cli_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_cli_a_SOURCES = \
   rpc/client.cpp \
   $(BITCOIN_CORE_H)
 
 # seeder library
 libbitcoin_seeder_a_CPPFLAGS = $(AM_CPPFLAGS) $(PIE_FLAGS) $(BITCOIN_SEEDER_INCLUDES)
 libbitcoin_seeder_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_seeder_a_SOURCES = \
   seeder/bitcoin.cpp \
   seeder/bitcoin.h \
   seeder/compat.h \
   seeder/db.cpp \
   seeder/db.h \
   seeder/dns.cpp \
   seeder/dns.h \
   seeder/strlcpy.h \
   seeder/util.h
 
 nodist_libbitcoin_util_a_SOURCES = $(srcdir)/obj/build.h
 #
 
 # bitcoind binary #
 bitcoind_SOURCES = bitcoind.cpp
 bitcoind_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 bitcoind_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 bitcoind_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 
 if TARGET_WINDOWS
 bitcoind_SOURCES += bitcoind-res.rc
 endif
 
 bitcoind_LDADD = \
   $(LIBBITCOIN_SERVER) \
   $(LIBBITCOIN_COMMON) \
   $(LIBUNIVALUE) \
   $(LIBBITCOIN_UTIL) \
   $(LIBBITCOIN_WALLET) \
   $(LIBBITCOIN_ZMQ) \
   $(LIBBITCOIN_CONSENSUS) \
   $(LIBBITCOIN_CRYPTO) \
   $(LIBLEVELDB) \
   $(LIBLEVELDB_SSE42) \
   $(LIBMEMENV) \
   $(LIBSECP256K1)
 
 bitcoind_LDADD += $(BOOST_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(ZMQ_LIBS)
 
 # bitcoin-cli binary #
 bitcoin_cli_SOURCES = bitcoin-cli.cpp
 bitcoin_cli_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(EVENT_CFLAGS)
 bitcoin_cli_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 bitcoin_cli_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 
 if TARGET_WINDOWS
 bitcoin_cli_SOURCES += bitcoin-cli-res.rc
 endif
 
 bitcoin_cli_LDADD = \
   $(LIBBITCOIN_CLI) \
   $(LIBUNIVALUE) \
   $(LIBBITCOIN_UTIL) \
   $(LIBBITCOIN_CRYPTO)
 
 bitcoin_cli_LDADD += $(BOOST_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(EVENT_LIBS)
 #
 
 # bitcoin-seeder binary #
 bitcoin_seeder_SOURCES = seeder/main.cpp
 bitcoin_seeder_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_SEEDER_INCLUDES)
 bitcoin_seeder_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 bitcoin_seeder_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 
 bitcoin_seeder_LDADD = \
   $(LIBBITCOIN_SEEDER) \
   $(LIBBITCOIN_COMMON) \
   $(LIBBITCOIN_UTIL) \
   $(LIBBITCOIN_CRYPTO)
 
 bitcoin_seeder_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 #
 
 # bitcoin-tx binary #
 bitcoin_tx_SOURCES = bitcoin-tx.cpp
 bitcoin_tx_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 bitcoin_tx_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 bitcoin_tx_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 
 if TARGET_WINDOWS
 bitcoin_tx_SOURCES += bitcoin-tx-res.rc
 endif
 
 bitcoin_tx_LDADD = \
   $(LIBUNIVALUE) \
   $(LIBBITCOIN_COMMON) \
   $(LIBBITCOIN_UTIL) \
   $(LIBBITCOIN_CONSENSUS) \
   $(LIBBITCOIN_CRYPTO) \
   $(LIBSECP256K1)
 
 bitcoin_tx_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 #
 
 # bitcoinconsensus library #
 if BUILD_BITCOIN_LIBS
 include_HEADERS = script/bitcoinconsensus.h
 libbitcoinconsensus_la_SOURCES = $(crypto_libbitcoin_crypto_base_a_SOURCES) $(libbitcoin_consensus_a_SOURCES)
 
 if GLIBC_BACK_COMPAT
   libbitcoinconsensus_la_SOURCES += compat/glibc_compat.cpp
 endif
 
 libbitcoinconsensus_la_LDFLAGS = $(AM_LDFLAGS) -no-undefined $(RELDFLAGS)
 libbitcoinconsensus_la_LIBADD = $(LIBSECP256K1)
 libbitcoinconsensus_la_CPPFLAGS = $(AM_CPPFLAGS) -I$(builddir)/obj -I$(srcdir)/secp256k1/include -DBUILD_BITCOIN_INTERNAL
 libbitcoinconsensus_la_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 
 endif
 #
 
 CTAES_DIST =  crypto/ctaes/bench.c
 CTAES_DIST += crypto/ctaes/ctaes.c
 CTAES_DIST += crypto/ctaes/ctaes.h
 CTAES_DIST += crypto/ctaes/README.md
 CTAES_DIST += crypto/ctaes/test.c
 
 CLEANFILES = $(EXTRA_LIBRARIES)
 
 CLEANFILES += *.gcda *.gcno
 CLEANFILES += compat/*.gcda compat/*.gcno
 CLEANFILES += consensus/*.gcda consensus/*.gcno
 CLEANFILES += crypto/*.gcda crypto/*.gcno
 CLEANFILES += policy/*.gcda policy/*.gcno
 CLEANFILES += primitives/*.gcda primitives/*.gcno
 CLEANFILES += script/*.gcda script/*.gcno
 CLEANFILES += support/*.gcda support/*.gcno
 CLEANFILES += univalue/*.gcda univalue/*.gcno
 CLEANFILES += wallet/*.gcda wallet/*.gcno
 CLEANFILES += wallet/test/*.gcda wallet/test/*.gcno
 CLEANFILES += zmq/*.gcda zmq/*.gcno
 
 DISTCLEANFILES = obj/build.h
 
 EXTRA_DIST = $(CTAES_DIST)
 
 clean-local:
 	-$(MAKE) -C secp256k1 clean
 	-$(MAKE) -C univalue clean
 	-rm -f leveldb/*/*.gcda leveldb/*/*.gcno leveldb/helpers/memenv/*.gcda leveldb/helpers/memenv/*.gcno
 	-rm -rf test/__pycache__
 
 .rc.o:
 	@test -f $(WINDRES)
 	## FIXME: How to get the appropriate modulename_CPPFLAGS in here?
 	$(AM_V_GEN) $(WINDRES) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(CPPFLAGS) -DWINDRES_PREPROC -i $< -o $@
 
 .mm.o:
 	$(AM_V_CXX) $(OBJCXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
 	  $(CPPFLAGS) $(AM_CXXFLAGS) $(QT_INCLUDES) $(AM_CXXFLAGS) $(PIE_FLAGS) $(CXXFLAGS) -c -o $@ $<
 
 check-symbols: $(bin_PROGRAMS)
 if GLIBC_BACK_COMPAT
 	@echo "Checking glibc back compat..."
 	$(AM_V_at) READELF=$(READELF) CPPFILT=$(CPPFILT) $(top_srcdir)/contrib/devtools/symbol-check.py < $(bin_PROGRAMS)
 endif
 
 check-security: $(bin_PROGRAMS)
 if HARDEN
 	@echo "Checking binary security..."
 	$(AM_V_at) READELF=$(READELF) OBJDUMP=$(OBJDUMP) $(top_srcdir)/contrib/devtools/security-check.py < $(bin_PROGRAMS)
 endif
 
 %.pb.cc %.pb.h: %.proto
 	@test -f $(PROTOC)
 	$(AM_V_GEN) $(PROTOC) --cpp_out=$(@D) --proto_path=$(<D) $<
 
 if EMBEDDED_LEVELDB
 include Makefile.leveldb.include
 endif
 
 if ENABLE_TESTS
 include Makefile.test.include
 endif
 
 if ENABLE_BENCH
 include Makefile.bench.include
 endif
 
 if ENABLE_QT
 include Makefile.qt.include
 endif
 
 if ENABLE_QT_TESTS
 include Makefile.qttest.include
 endif
diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 74ea379f5..44aaedbc5 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -1,197 +1,198 @@
 # Copyright (c) 2013-2016 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 TESTS += test/test_bitcoin
 LOG_DRIVER = $(srcdir)/test/test-bitcoin-driver
 EXTRA_DIST += test/test-bitcoin-driver
 bin_PROGRAMS += test/test_bitcoin
 noinst_PROGRAMS += test/test_bitcoin_fuzzy
 TEST_SRCDIR = test
 TEST_BINARY=test/test_bitcoin$(EXEEXT)
 
 JSON_TEST_FILES = \
   test/data/script_tests.json \
   test/data/base58_keys_valid.json \
   test/data/base58_encode_decode.json \
   test/data/base58_keys_invalid.json \
   test/data/tx_invalid.json \
   test/data/tx_valid.json \
   test/data/sighash.json
 
 RAW_TEST_FILES =
 
 GENERATED_TEST_FILES = $(JSON_TEST_FILES:.json=.json.h) $(RAW_TEST_FILES:.raw=.raw.h)
 
 # test_bitcoin binary #
 BITCOIN_TESTS =\
-  test/arith_uint256_tests.cpp \
   test/scriptnum10.h \
   test/addrman_tests.cpp \
-  test/amount_tests.cpp \
   test/allocator_tests.cpp \
+  test/amount_tests.cpp \
+  test/arith_uint256_tests.cpp \
+  test/avalanche_tests.cpp \
   test/base32_tests.cpp \
   test/base58_tests.cpp \
   test/base64_tests.cpp \
   test/bip32_tests.cpp \
   test/blockcheck_tests.cpp \
   test/blockencodings_tests.cpp \
   test/blockindex_tests.cpp \
   test/blockstatus_tests.cpp \
   test/bloom_tests.cpp \
   test/bswap_tests.cpp \
   test/cashaddr_tests.cpp \
   test/cashaddrenc_tests.cpp \
   test/checkdatasig_tests.cpp \
   test/checkpoints_tests.cpp \
   test/checkqueue_tests.cpp \
   test/coins_tests.cpp \
   test/compress_tests.cpp \
   test/config_tests.cpp \
   test/core_io_tests.cpp \
   test/crypto_tests.cpp \
   test/cuckoocache_tests.cpp \
   test/dbwrapper_tests.cpp \
   test/DoS_tests.cpp \
   test/dstencode_tests.cpp \
   test/excessiveblock_tests.cpp \
   test/feerate_tests.cpp \
   test/getarg_tests.cpp \
   test/hash_tests.cpp \
   test/inv_tests.cpp \
   test/jsonutil.cpp \
   test/jsonutil.h \
   test/key_tests.cpp \
   test/limitedmap_tests.cpp \
   test/main_tests.cpp \
   test/mempool_tests.cpp \
   test/merkle_tests.cpp \
   test/miner_tests.cpp \
   test/monolith_opcodes.cpp \
   test/multisig_tests.cpp \
   test/net_tests.cpp \
   test/netbase_tests.cpp \
   test/pmt_tests.cpp \
   test/policyestimator_tests.cpp \
   test/pow_tests.cpp \
   test/prevector_tests.cpp \
   test/raii_event_tests.cpp \
   test/random_tests.cpp \
   test/reverselock_tests.cpp \
   test/rpc_tests.cpp \
   test/rwcollection_tests.cpp \
   test/sanity_tests.cpp \
   test/scheduler_tests.cpp \
   test/script_commitment_tests.cpp \
   test/script_P2SH_tests.cpp \
   test/script_tests.cpp \
   test/scriptflags.cpp \
   test/scriptflags.h \
   test/scriptnum_tests.cpp \
   test/serialize_tests.cpp \
   test/sigencoding_tests.cpp \
   test/sighash_tests.cpp \
   test/sighashtype_tests.cpp \
   test/sigopcount_tests.cpp \
   test/sigutil.cpp \
   test/sigutil.h \
   test/skiplist_tests.cpp \
   test/streams_tests.cpp \
   test/sync_tests.cpp \
   test/test_bitcoin.cpp \
   test/test_bitcoin.h \
   test/test_bitcoin_main.cpp \
   test/testutil.cpp \
   test/testutil.h \
   test/timedata_tests.cpp \
   test/transaction_tests.cpp \
   test/txvalidationcache_tests.cpp \
   test/versionbits_tests.cpp \
   test/uint256_tests.cpp \
   test/undo_tests.cpp \
   test/univalue_tests.cpp \
   test/util_tests.cpp \
   test/validation_tests.cpp \
   test/work_comparator_tests.cpp \
   rpc/test/server_tests.cpp
 
 if ENABLE_WALLET
 BITCOIN_TESTS += \
   wallet/test/wallet_test_fixture.cpp \
   wallet/test/wallet_test_fixture.h \
   wallet/test/accounting_tests.cpp \
   wallet/test/wallet_tests.cpp \
   wallet/test/walletdb_tests.cpp \
   wallet/test/crypto_tests.cpp
 endif
 
 test_test_bitcoin_SOURCES = $(BITCOIN_TESTS) $(JSON_TEST_FILES) $(RAW_TEST_FILES)
 test_test_bitcoin_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -I$(builddir)/test/ $(TESTDEFS) $(EVENT_CFLAGS)
 test_test_bitcoin_LDADD =
 if ENABLE_WALLET
 test_test_bitcoin_LDADD += $(LIBBITCOIN_WALLET)
 endif
 
 test_test_bitcoin_LDADD += $(LIBBITCOIN_SERVER) $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) \
   $(LIBLEVELDB) $(LIBLEVELDB_SSE42) $(LIBMEMENV) $(BOOST_LIBS) $(BOOST_UNIT_TEST_FRAMEWORK_LIB) $(LIBSECP256K1) $(EVENT_LIBS) $(EVENT_PTHREADS_LIBS)
 test_test_bitcoin_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 
 test_test_bitcoin_LDADD += $(LIBBITCOIN_CONSENSUS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS)
 test_test_bitcoin_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS) -static
 
 if ENABLE_ZMQ
 test_test_bitcoin_LDADD += $(ZMQ_LIBS)
 endif
 #
 
 # test_bitcoin_fuzzy binary #
 test_test_bitcoin_fuzzy_SOURCES = test/test_bitcoin_fuzzy.cpp
 test_test_bitcoin_fuzzy_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_test_bitcoin_fuzzy_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_test_bitcoin_fuzzy_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 
 test_test_bitcoin_fuzzy_LDADD = \
   $(LIBUNIVALUE) \
   $(LIBBITCOIN_SERVER) \
   $(LIBBITCOIN_COMMON) \
   $(LIBBITCOIN_UTIL) \
   $(LIBBITCOIN_CONSENSUS) \
   $(LIBBITCOIN_CRYPTO) \
   $(LIBSECP256K1)
 
 test_test_bitcoin_fuzzy_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 #
 
 nodist_test_test_bitcoin_SOURCES = $(GENERATED_TEST_FILES)
 
 $(BITCOIN_TESTS): $(GENERATED_TEST_FILES)
 
 CLEAN_BITCOIN_TEST = test/*.gcda test/*.gcno $(GENERATED_TEST_FILES)
 
 CLEANFILES += $(CLEAN_BITCOIN_TEST)
 
 bitcoin_test: $(TEST_BINARY)
 
 bitcoin_test_check: $(TEST_BINARY) FORCE
 	$(MAKE) check-TESTS TESTS=$^
 
 bitcoin_test_clean : FORCE
 	rm -f $(CLEAN_BITCOIN_TEST) $(test_test_bitcoin_OBJECTS) $(TEST_BINARY)
 
 check-local:
 	@echo "Running test/util/bitcoin-util-test.py..."
 	$(top_builddir)/test/util/bitcoin-util-test.py
 	$(AM_V_at)$(MAKE) $(AM_MAKEFLAGS) -C secp256k1 check
 if EMBEDDED_UNIVALUE
 	$(AM_V_at)$(MAKE) $(AM_MAKEFLAGS) -C univalue check
 endif
 
 %.json.h: %.json
 	@$(MKDIR_P) $(@D)
 	@{ \
 	 echo "namespace json_tests{" && \
 	 echo "static unsigned const char $(*F)[] = {" && \
 	 $(HEXDUMP) -v -e '8/1 "0x%02x, "' -e '"\n"' $< | $(SED) -e 's/0x  ,//g' && \
 	 echo "};};"; \
 	} > "$@.new" && mv -f "$@.new" "$@"
 	@echo "Generated $@"
diff --git a/src/avalanche_impl.h b/src/avalanche_impl.h
new file mode 100644
index 000000000..12eca8f9f
--- /dev/null
+++ b/src/avalanche_impl.h
@@ -0,0 +1,82 @@
+// Copyright (c) 2018 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_AVALANCHE_IMPL_H
+#define BITCOIN_AVALANCHE_IMPL_H
+
+#include <cstdint>
+
+namespace {
+/**
+ * Finalization score.
+ */
+static int AVALANCHE_FINALIZATION_SCORE = 128;
+
+/**
+ * Vote history.
+ */
+struct VoteRecord {
+private:
+    // Historical record of votes.
+    uint16_t votes;
+
+    // confidence's LSB bit is the result. Higher bits are actual confidence
+    // score.
+    uint16_t confidence;
+
+    /**
+     * Return the number of bits set in an integer value.
+     * TODO: There are compiler intrinsics to do that, but we'd need to get them
+     * detected so this will do for now.
+     */
+    static uint32_t countBits(uint32_t value) {
+        uint32_t count = 0;
+        while (value) {
+            // If the value is non zero, then at least one bit is set.
+            count++;
+
+            // Clear the rightmost bit set.
+            value &= (value - 1);
+        }
+
+        return count;
+    }
+
+public:
+    VoteRecord() : votes(0xaaaa), confidence(0) {}
+
+    bool isValid() const { return confidence & 0x01; }
+
+    uint16_t getConfidence() const { return confidence >> 1; }
+    bool hasFinalized() const {
+        return getConfidence() >= AVALANCHE_FINALIZATION_SCORE;
+    }
+
+    bool registerVote(bool vote) {
+        votes = (votes << 1) | vote;
+
+        auto bits = countBits(votes & 0xff);
+        bool yes = bits > 6;
+        bool no = bits < 2;
+        if (!yes && !no) {
+            // The vote is inconclusive.
+            return false;
+        }
+
+        if (isValid() == yes) {
+            // If the vote is in agreement with our internal status, increase
+            // confidence.
+            confidence += 2;
+        } else {
+            // The vote did not agree with our internal state, in that case,
+            // reset confidence.
+            confidence = yes;
+        }
+
+        return true;
+    }
+};
+}
+
+#endif // BITCOIN_AVALANCHE_IMPL_H
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index c00c17ceb..6bbf10271 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -1,168 +1,169 @@
 # Copyright (c) 2018 The Bitcoin developers
 
 project(bitcoin-test)
 
 # Process json files.
 file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/data")
 
 find_program(PYTHON python)
 function(gen_json_header NAME)
 	set(HEADERS "")
 	foreach(f ${ARGN})
 		set(h "${CMAKE_CURRENT_BINARY_DIR}/${f}.h")
 
 		# Get the proper name for the test variable.
 		get_filename_component(TEST_NAME ${f} NAME_WE)
 		add_custom_command(OUTPUT ${h}
 			COMMAND ${PYTHON}
 			ARGS
 				"${CMAKE_CURRENT_SOURCE_DIR}/data/generate_header.py"
 				"${TEST_NAME}"
 				"${CMAKE_CURRENT_SOURCE_DIR}/${f}" > ${h}
 			MAIN_DEPENDENCY ${f}
 			DEPENDS
 				"data/generate_header.py"
 			VERBATIM
 		)
 		list(APPEND HEADERS ${h})
 	endforeach(f)
 	set(${NAME} "${HEADERS}" PARENT_SCOPE)
 endfunction()
 
 gen_json_header(JSON_HEADERS
 	data/script_tests.json
 	data/base58_keys_valid.json
 	data/base58_encode_decode.json
 	data/base58_keys_invalid.json
 	data/tx_invalid.json
 	data/tx_valid.json
 	data/sighash.json
 )
 
 include(TestSuite)
 create_test_suite(bitcoin)
 add_dependencies(check check-bitcoin)
 
 add_test_to_suite(bitcoin test_bitcoin
-	arith_uint256_tests.cpp
 	addrman_tests.cpp
-	amount_tests.cpp
 	allocator_tests.cpp
+	amount_tests.cpp
+	arith_uint256_tests.cpp
+	avalanche_tests.cpp
 	base32_tests.cpp
 	base58_tests.cpp
 	base64_tests.cpp
 	bip32_tests.cpp
 	blockcheck_tests.cpp
 	blockencodings_tests.cpp
 	blockindex_tests.cpp
 	blockstatus_tests.cpp
 	bloom_tests.cpp
 	bswap_tests.cpp
 	cashaddr_tests.cpp
 	cashaddrenc_tests.cpp
 	checkdatasig_tests.cpp
 	checkpoints_tests.cpp
 	checkqueue_tests.cpp
 	coins_tests.cpp
 	compress_tests.cpp
 	config_tests.cpp
 	core_io_tests.cpp
 	crypto_tests.cpp
 	cuckoocache_tests.cpp
 	dbwrapper_tests.cpp
 	DoS_tests.cpp
 	dstencode_tests.cpp
 	excessiveblock_tests.cpp
 	feerate_tests.cpp
 	getarg_tests.cpp
 	hash_tests.cpp
 	inv_tests.cpp
 	jsonutil.cpp
 	key_tests.cpp
 	limitedmap_tests.cpp
 	main_tests.cpp
 	mempool_tests.cpp
 	merkle_tests.cpp
 	miner_tests.cpp
 	monolith_opcodes.cpp
 	multisig_tests.cpp
 	net_tests.cpp
 	netbase_tests.cpp
 	pmt_tests.cpp
 	policyestimator_tests.cpp
 	pow_tests.cpp
 	prevector_tests.cpp
 	raii_event_tests.cpp
 	random_tests.cpp
 	reverselock_tests.cpp
 	rpc_tests.cpp
 	rwcollection_tests.cpp
 	sanity_tests.cpp
 	scheduler_tests.cpp
 	script_commitment_tests.cpp
 	script_P2SH_tests.cpp
 	script_tests.cpp
 	scriptflags.cpp
 	scriptnum_tests.cpp
 	serialize_tests.cpp
 	sigencoding_tests.cpp
 	sighash_tests.cpp
 	sighashtype_tests.cpp
 	sigopcount_tests.cpp
 	sigutil.cpp
 	skiplist_tests.cpp
 	streams_tests.cpp
 	sync_tests.cpp
 	test_bitcoin.cpp
 	test_bitcoin_main.cpp
 	testutil.cpp
 	timedata_tests.cpp
 	transaction_tests.cpp
 	txvalidationcache_tests.cpp
 	versionbits_tests.cpp
 	uint256_tests.cpp
 	undo_tests.cpp
 	univalue_tests.cpp
 	util_tests.cpp
 	validation_tests.cpp
 	work_comparator_tests.cpp
 
 	# RPC Tests
 	../rpc/test/server_tests.cpp
 
 	# Tests generated from JSON
 	${JSON_HEADERS}
 )
 
 target_include_directories(test_bitcoin
 	PUBLIC
 		# To access the generated json headers.
 		${CMAKE_CURRENT_BINARY_DIR}
 )
 
 find_package(Boost 1.58 REQUIRED unit_test_framework)
 
 target_link_libraries(test_bitcoin Boost::unit_test_framework rpcclient server)
 
 # We need to detect if the BOOST_TEST_DYN_LINK flag is required.
 set(CMAKE_REQUIRED_LIBRARIES Boost::unit_test_framework)
 check_cxx_source_compiles("
 	#define BOOST_TEST_DYN_LINK
 	#define BOOST_TEST_MAIN
 	#include <boost/test/unit_test.hpp>
 " BOOST_TEST_DYN_LINK)
 
 if(BOOST_TEST_DYN_LINK)
 	target_compile_definitions(test_bitcoin PRIVATE BOOST_TEST_DYN_LINK)
 endif(BOOST_TEST_DYN_LINK)
 
 if(BUILD_BITCOIN_WALLET)
 	target_sources(test_bitcoin
 		PRIVATE
 			../wallet/test/wallet_test_fixture.cpp
 			../wallet/test/accounting_tests.cpp
 			../wallet/test/wallet_tests.cpp
 			../wallet/test/walletdb_tests.cpp
 			../wallet/test/crypto_tests.cpp
 	)
 endif()
diff --git a/src/test/avalanche_tests.cpp b/src/test/avalanche_tests.cpp
new file mode 100644
index 000000000..2b4e7c89a
--- /dev/null
+++ b/src/test/avalanche_tests.cpp
@@ -0,0 +1,69 @@
+// Copyright (c) 2010 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "avalanche_impl.h"
+
+#include "test/test_bitcoin.h"
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_FIXTURE_TEST_SUITE(avalanche_tests, BasicTestingSetup)
+
+#define REGISTER_VOTE_AND_CHECK(vr, vote, state, finalized, confidence)        \
+    vr.registerVote(vote);                                                     \
+    BOOST_CHECK_EQUAL(vr.isValid(), state);                                    \
+    BOOST_CHECK_EQUAL(vr.hasFinalized(), finalized);                           \
+    BOOST_CHECK_EQUAL(vr.getConfidence(), confidence);
+
+BOOST_AUTO_TEST_CASE(vote_record) {
+    VoteRecord vr;
+
+    // Check initial state.
+    BOOST_CHECK_EQUAL(vr.isValid(), false);
+    BOOST_CHECK_EQUAL(vr.hasFinalized(), false);
+    BOOST_CHECK_EQUAL(vr.getConfidence(), 0);
+
+    // We register one vote for, which keep things at 4/4.
+    REGISTER_VOTE_AND_CHECK(vr, true, false, false, 0);
+
+    // One more and we are at 5/3.
+    REGISTER_VOTE_AND_CHECK(vr, true, false, false, 0);
+
+    // One more and we are at 5/3.
+    REGISTER_VOTE_AND_CHECK(vr, true, false, false, 0);
+
+    // One more and we are at 6/2.
+    REGISTER_VOTE_AND_CHECK(vr, true, false, false, 0);
+
+    // One more and we are at 6/2.
+    REGISTER_VOTE_AND_CHECK(vr, true, false, false, 0);
+
+    // Next vote will flip state, and confidence will increase as long as we
+    // vote yes.
+    for (int i = 0; i < AVALANCHE_FINALIZATION_SCORE; i++) {
+        REGISTER_VOTE_AND_CHECK(vr, true, true, false, i);
+    }
+
+    // The next vote will finalize the decision.
+    REGISTER_VOTE_AND_CHECK(vr, false, true, true,
+                            AVALANCHE_FINALIZATION_SCORE);
+
+    // Now that we have two no votes, confidence stop increasing.
+    for (int i = 0; i < 5; i++) {
+        REGISTER_VOTE_AND_CHECK(vr, false, true, true,
+                                AVALANCHE_FINALIZATION_SCORE);
+    }
+
+    // Next vote will flip state, and confidence will increase as long as we
+    // vote no.
+    for (int i = 0; i < AVALANCHE_FINALIZATION_SCORE; i++) {
+        REGISTER_VOTE_AND_CHECK(vr, false, false, false, i);
+    }
+
+    // The next vote will finalize the decision.
+    REGISTER_VOTE_AND_CHECK(vr, true, false, true,
+                            AVALANCHE_FINALIZATION_SCORE);
+}
+
+BOOST_AUTO_TEST_SUITE_END()