diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..aa63c79
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,119 @@
+#!/usr/bin/make -f
+
+BUILD_DIR := build
+OPTIMIZE_FLAGS ?= -g -O3
+TEST_OPTIMIZE_FLAGS ?= -g -O0
+JS_OPTIMIZE_FLAGS ?= -O3
+CC = gcc
+EMCC = emcc
+TARGET := $(BUILD_DIR)/libolm.so
+JS_TARGET := javascript/olm.js
+
+JS_EXPORTED_FUNCTIONS := javascript/exported_functions.json
+
+PUBLIC_HEADERS := include/olm/olm.hh
+
+SOURCES := $(wildcard src/*.cpp) $(wildcard src/*.c)
+OBJECTS := $(patsubst src/%,$(BUILD_DIR)/%,$(patsubst %.c,%.o,$(patsubst %.cpp,%.o,$(SOURCES))))
+TEST_SOURCES := $(wildcard tests/test_*.cpp) $(wildcard tests/test_*.c)
+TEST_BINARIES := $(patsubst tests/%,$(BUILD_DIR)/%,$(patsubst %.c,%,$(patsubst %.cpp,%,$(TEST_SOURCES))))
+JS_OBJECTS := $(patsubst %.o,%.js.bc,$(OBJECTS))
+JS_PRE := $(wildcard javascript/*pre.js)
+JS_POST := $(wildcard javascript/*post.js)
+
+CPPFLAGS += -Iinclude -Ilib
+CFLAGS += -Wall --std=c89 -fPIC
+CXXFLAGS += -Wall --std=c++11 -fPIC
+LDFLAGS += -Wall
+
+EMCCFLAGS = --closure 1 --memory-init-file 0 -s NO_FILESYSTEM=1 -s INVOKE_RUN=0
+# NO_BROWSER is kept for compatibility with emscripten 1.35.24, but is no
+# longer needed.
+EMCCFLAGS += -s NO_BROWSER=1
+
+EMCC.c = $(EMCC) $(CFLAGS) $(CPPFLAGS) -c
+EMCC.cc = $(EMCC) $(CXXFLAGS) $(CPPFLAGS) -c
+EMCC_LINK = $(EMCC) $(LDFLAGS) $(EMCCFLAGS)
+
+# generate .d files when compiling
+CPPFLAGS += -MMD
+
+### per-target variables
+
+$(OBJECTS): CFLAGS += $(OPTIMIZE_FLAGS)
+$(OBJECTS): CXXFLAGS += $(OPTIMIZE_FLAGS)
+$(TARGET): LDFLAGS += $(OPTIMIZE_FLAGS)
+
+$(TEST_BINARIES): CPPFLAGS += -Itests/include
+$(TEST_BINARIES): LDFLAGS += $(TEST_OPTIMIZE_FLAGS) -L$(BUILD_DIR)
+
+$(JS_OBJECTS): CFLAGS += $(JS_OPTIMIZE_FLAGS)
+$(JS_OBJECTS): CXXFLAGS += $(JS_OPTIMIZE_FLAGS)
+$(JS_TARGET): LDFLAGS += $(JS_OPTIMIZE_FLAGS)
+
+### top-level targets
+
+lib: $(TARGET)
+.PHONY: lib
+
+$(TARGET): $(OBJECTS)
+	$(CXX) $(LDFLAGS) --shared -fPIC \
+	    -Wl,--version-script,version_script.ver \
+            $(OUTPUT_OPTION) $(OBJECTS)
+
+js: $(JS_TARGET)
+.PHONY: js
+
+$(JS_TARGET): $(JS_OBJECTS) $(JS_PRE) $(JS_POST) $(JS_EXPORTED_FUNCTIONS)
+	$(EMCC_LINK) \
+	       --pre-js $(JS_PRE) --post-js $(JS_POST) \
+	       -s "EXPORTED_FUNCTIONS=@$(JS_EXPORTED_FUNCTIONS)" \
+               $(JS_OBJECTS) -o $@
+
+clean:;
+	rm -rf $(OBJECTS) $(OBJECTS:.o=.d) \
+               $(TEST_BINARIES) $(TEST_BINARIES:=.d) \
+               $(JS_OBJECTS) $(JS_OBJECTS:=.d) $(JS_TARGET) \
+               $(JS_EXPORTED_FUNCTIONS) \
+               $(TARGET)
+
+build_tests: $(TEST_BINARIES)
+
+test: build_tests
+	for i in $(TEST_BINARIES); do \
+	    echo $$i; \
+	    $$i || exit $$?; \
+	done
+
+$(JS_EXPORTED_FUNCTIONS): $(PUBLIC_HEADERS)
+	perl -MJSON -ne '/(olm_[^( ]*)\(/ && push @f, "_$$1"; END { print encode_json \@f }' $^ > $@.tmp
+	mv $@.tmp $@
+
+all: test js lib
+.PHONY: lib
+
+### rules for building objects
+$(BUILD_DIR)/%.o: src/%.c
+	$(COMPILE.c) $(OUTPUT_OPTION) $<
+
+$(BUILD_DIR)/%.o: src/%.cpp
+	$(COMPILE.cc) $(OUTPUT_OPTION) $<
+
+$(BUILD_DIR)/%.js.bc: src/%.c
+	$(EMCC.c) $(OUTPUT_OPTION) $<
+
+$(BUILD_DIR)/%.js.bc: src/%.cpp
+	$(EMCC.cc) $(OUTPUT_OPTION) $<
+
+$(BUILD_DIR)/%: tests/%.c $(OBJECTS)
+	$(LINK.c) $< $(OBJECTS) $(LOADLIBES) $(LDLIBS) -o $@
+
+$(BUILD_DIR)/%: tests/%.cpp $(OBJECTS)
+	$(LINK.cc) $< $(OBJECTS) $(LOADLIBES) $(LDLIBS) -o $@
+
+
+### dependencies
+
+-include $(OBJECTS:.o=.d)
+-include $(JS_OBJECTS:.bc=.d)
+-include $(TEST_BINARIES:=.d)
diff --git a/README.rst b/README.rst
index b2f48da..0f3ae4f 100644
--- a/README.rst
+++ b/README.rst
@@ -14,20 +14,19 @@ To build olm as a shared library run:
 
 .. code:: bash
 
-    ./build_shared_library.py
+    make
 
 To run the tests run:
 
 .. code:: bash
 
-   ./test.py
-
+    make test
 
 To build the javascript bindings, install emscripten from http://kripken.github.io/emscripten-site/ and then run:
 
 .. code:: bash
 
-    javascript/build.py  # builds javascript/olm.js
+    make js
     npm pack javascript  # packages olm.js into olm-x.y.z.tgz
 
 Remember to make a tag after releasing a tarball:
@@ -43,6 +42,11 @@ Design
 Olm is designed to be easy port to different platforms and to be easy
 to write bindings for.
 
+It was originally implemented in C++, with a plain-C layer providing the public
+API. As development has progressed, it has become clear that C++ gives little
+advantage, and new functionality is being added in C, with C++ parts being
+rewritten as the need ariases.
+
 Error Handling
 ~~~~~~~~~~~~~~
 
@@ -78,13 +82,13 @@ the ratchet. While this decreases the performance it makes it much easier
 to compile the library for different architectures.
 
 What's an olm?
-~~~~~~~~~~~~~~
+--------------
 
 It's a really cool species of European troglodytic salamander.
 http://www.postojnska-jama.eu/en/come-and-visit-us/vivarium-proteus/
 
 Legal Notice
-~~~~~~~~~~~~
+------------
 
 The software may be subject to the U.S. export control laws and regulations
 and by downloading the software the user certifies that he/she/it is
diff --git a/build_shared_library.py b/build_shared_library.py
deleted file mode 100755
index 911c7b3..0000000
--- a/build_shared_library.py
+++ /dev/null
@@ -1,36 +0,0 @@
-#! /usr/bin/env python
-# Copyright 2015 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import subprocess
-import glob
-import os
-import sys
-
-if not os.path.exists("build"):
-    os.mkdir("build")
-
-source_files = glob.glob("src/*.cpp")
-
-compile_args = "g++ -Wall -O3 -Iinclude -Ilib --std=c++11 --shared -fPIC".split()
-compile_args += source_files
-compile_args += sys.argv[1:]
-
-library = "build/libolm.so"
-
-def run(args):
-    print " ".join(args)
-    subprocess.check_call(args)
-
-run(compile_args + ["-o", library])
diff --git a/javascript/build.py b/javascript/build.py
deleted file mode 100755
index f253acb..0000000
--- a/javascript/build.py
+++ /dev/null
@@ -1,74 +0,0 @@
-#! /usr/bin/env python
-# Copyright 2015 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import subprocess
-import glob
-import os
-import sys
-import re
-import json
-
-
-os.chdir(os.path.dirname(os.path.dirname(os.path.realpath(__file__))))
-source_files = glob.glob("src/*.cpp")
-pre_js, = glob.glob("javascript/*pre.js")
-post_js, = glob.glob("javascript/*post.js")
-
-functions = set()
-RE_FUNCTION=re.compile("(olm_[^( ]*)\\(")
-with open("include/olm/olm.hh") as header:
-    for line in header:
-        match = RE_FUNCTION.search(line)
-        if match:
-            functions.add(match.groups()[0])
-
-
-exported_functions = os.path.abspath("javascript/exported_functions.json")
-with open(exported_functions, "w") as json_file:
-    json.dump(["_" + function for function in functions], json_file)
-
-
-emcc = os.environ.get("EMCC", "emcc")
-optimize_opts = os.environ.get("OPTIMIZE_FLAGS", "-O3")
-
-compile_args = [emcc]
-compile_args += optimize_opts.split()
-compile_args += ["-Wall"]
-compile_args += """
-    -Iinclude
-    -Ilib
-    -std=c++11
-    --closure 1
-    --memory-init-file 0
-    -s NO_FILESYSTEM=1
-    -s INVOKE_RUN=0
-""".split()
-# NO_BROWSER is kept for compatibility with emscripten 1.35.24, but is no
-# longer needed.
-compile_args += ("-s","NO_BROWSER=1")
-compile_args += source_files
-compile_args += ("--pre-js", pre_js)
-compile_args += ("--post-js", post_js)
-compile_args += ("-s", "EXPORTED_FUNCTIONS=@" + exported_functions)
-compile_args += sys.argv[1:]
-
-library = "javascript/olm.js"
-
-def run(args):
-    print args
-    print " ".join(args)
-    subprocess.check_call(args)
-
-run(compile_args + ["-o", library])
diff --git a/javascript/package.json b/javascript/package.json
index dc16e45..710d46d 100644
--- a/javascript/package.json
+++ b/javascript/package.json
@@ -8,7 +8,7 @@
     "README.md"
   ],
   "scripts": {
-    "build": "./build.py",
+    "build": "make -C .. js",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "repository": {
diff --git a/src/crypto.cpp b/src/crypto.cpp
index 3801e93..5a2689f 100644
--- a/src/crypto.cpp
+++ b/src/crypto.cpp
@@ -303,14 +303,14 @@ void olm::hkdf_sha256(
         salt = HKDF_DEFAULT_SALT;
         salt_length = sizeof(HKDF_DEFAULT_SALT);
     }
-    /* Expand */
+    /* Extract */
     hmac_sha256_key(salt, salt_length, hmac_key);
     hmac_sha256_init(&context, hmac_key);
     ::sha256_update(&context, input, input_length);
     hmac_sha256_final(&context, hmac_key, step_result);
     hmac_sha256_key(step_result, olm::SHA256_OUTPUT_LENGTH, hmac_key);
 
-    /* Extract */
+    /* Expand */
     hmac_sha256_init(&context, hmac_key);
     ::sha256_update(&context, info, info_length);
     ::sha256_update(&context, &iteration, 1);
diff --git a/test.py b/test.py
deleted file mode 100755
index 83efe00..0000000
--- a/test.py
+++ /dev/null
@@ -1,38 +0,0 @@
-#! /usr/bin/env python
-# Copyright 2015 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import glob
-import os
-import subprocess
-import sys
-
-if not os.path.exists("build/libolm.so"):
-    print >> sys.stderr, \
-        "libolm has not been built. Run ./build_shared_library.py first."
-    exit(1)
-
-test_files = glob.glob("tests/test_*.cpp")
-
-compile_args = ("g++ -g -O0 -Itests/include -Iinclude -Ilib --std=c++11 "+
-                "-L build").split()
-
-def run(args, *xargs, **kwargs):
-    print " ".join(args)
-    subprocess.check_call(args, *xargs, **kwargs)
-
-for test_file in test_files:
-    exe_file = "build/" + test_file[6:-4]
-    run(compile_args + [test_file, "-lolm", "-o", exe_file])
-    run([exe_file], env={'LD_LIBRARY_PATH':'./build'})
diff --git a/version_script.ver b/version_script.ver
new file mode 100644
index 0000000..3aec5f6
--- /dev/null
+++ b/version_script.ver
@@ -0,0 +1,9 @@
+# this is a 'version script' for the linker which tells it to only export
+# symbols starting 'olm_'.
+
+{
+    global:
+        olm_*;
+    local:
+        *;
+};