diff --git a/.github/workflows/android.yml b/.github/workflows/android.yml
new file mode 100644
index 0000000..366bd8a
--- /dev/null
+++ b/.github/workflows/android.yml
@@ -0,0 +1,81 @@
+name: Android
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+env:
+  BUILD_TYPE: Release
+
+jobs:
+  build:
+    runs-on: macos-latest
+    timeout-minutes: 30
+    strategy:
+      matrix:
+        abi: [x86_64, x86, arm64-v8a, armeabi-v7a]
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: true
+
+      - name: Build ${{matrix.abi}}
+        run: |
+          sh build-android.sh ${{matrix.abi}} -DBUILD_TESTSUITE=OFF -DCMAKE_INSTALL_PREFIX:PATH="$HOME/android/${{matrix.abi}}"
+          cmake --install build-${{matrix.abi}}
+      - name: Archive artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: android
+          path: ~/android/
+
+  test:
+    timeout-minutes: 30
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        abi: [x86_64]
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: true
+
+      - name: AVD cache
+        uses: actions/cache@v3
+        id: avd-cache
+        with:
+          path: |
+            ~/.android/avd/*
+            ~/.android/adb*
+          key: hostos-${{matrix.os}}-api-21-abi-${{matrix.abi}}
+      - name: Create AVD and generate snapshot for caching
+        if: steps.avd-cache.outputs.cache-hit != 'true'
+        uses: reactivecircus/android-emulator-runner@v2
+        with:
+          emulator-options: -no-window -gpu swiftshader_indirect -no-audio -no-boot-anim -camera-back none
+          api-level: 21
+          arch: ${{matrix.abi}}
+          ndk: 25.2.9519653
+          force-avd-creation: false
+          disable-animations: false
+          script: echo "Generated AVD snapshot for caching."
+      - name: Run tests
+        uses: reactivecircus/android-emulator-runner@v2
+        with:
+          emulator-options: -no-snapshot-save -no-window -gpu swiftshader_indirect -no-audio -no-boot-anim -camera-back none
+          api-level: 21
+          arch: ${{matrix.abi}}
+          ndk: 25.2.9519653
+          force-avd-creation: false
+          disable-animations: true
+          script: sh build-android.sh ${{matrix.abi}} -DCMAKE_INSTALL_PREFIX:PATH="$HOME/android/${{matrix.abi}}"
+      - name: Archive artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: android-testsuite-${{matrix.os}}-${{matrix.abi}}
+          path: build-${{matrix.abi}}/testsuite/log.txt
diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
new file mode 100644
index 0000000..184f5c0
--- /dev/null
+++ b/.github/workflows/cmake.yml
@@ -0,0 +1,31 @@
+name: CMake
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+env:
+  BUILD_TYPE: Release
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: true
+
+      - name: Configure CMake
+        run: cmake -S . -B build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}
+
+      - name: Build
+        run: cmake --build build --config ${{env.BUILD_TYPE}}
+
+      - name: Test
+        run: ctest --test-dir build -C ${{env.BUILD_TYPE}} -V
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..11f6d31
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+/out/
+/.vs/
+/.vscode/
+/build/
+/build-*/
+/Testing/
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..3a9a4aa
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "lighter"]
+	path = lighter
+	url = git@github.com:maroontress/lighter.git
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..8aeea7a
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,14 @@
+cmake_minimum_required(VERSION 3.24)
+
+project("mimicssl-md5" VERSION 1.0.0)
+
+add_compile_options("$<$<CXX_COMPILER_ID:MSVC>:/utf-8>")
+
+add_subdirectory(libmimicssl-md5)
+add_subdirectory(mimicssl-md5-cli)
+
+option(BUILD_TESTSUITE "Build testsuite" ON)
+if (${BUILD_TESTSUITE})
+  include(CTest)
+  add_subdirectory(testsuite)
+endif()
diff --git a/COPYRIGHT.md b/COPYRIGHT.md
new file mode 100644
index 0000000..1800b89
--- /dev/null
+++ b/COPYRIGHT.md
@@ -0,0 +1,23 @@
+Copyright (c) 2023 Maroontress Fast Software. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the
+   distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS *AS IS* AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
+BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e89d27f
--- /dev/null
+++ b/README.md
@@ -0,0 +1,76 @@
+# MimicSSL-MD5
+
+This is an [MD5][wikipedia::md5] implementation in C23, and its API is
+compatible with [OpenSSL 1.1][openssl::md5_init]. See the
+[RFC 1321][ietf::rfc1321] for the MD5 specifications.
+
+Note that the current implementation works only on little-endian platforms.
+
+## Example
+
+An example usage would be as follows:
+
+```c
+⋮
+MD5_CTX ctx;
+uint8_t md[16];
+char buffer[1024];
+
+MD5_Init(&ctx);
+for (;;) {
+    size_t size = fread(buffer, 1, sizeof(buffer), file);
+    if (size == 0) {
+        break;
+    }
+    MD5_Update(&ctx, buffer, size);
+}
+MD5_Final(md, &ctx);
+⋮
+```
+
+## Build
+
+This repository uses [lighter][maroontress::lighter] for testing as a sub-module
+of Git. Therefore, clone it as follows:
+
+```plaintext
+git clone --recursive URL
+```
+
+Then build the library as follows:
+
+```textplain
+cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
+cmake --build build --config Release
+ctest --test-dir build -C Release
+```
+
+## Build for Android
+
+Set environment variables `ANDROID_HOME` and `ANDROID_NDK` appropriately. For
+example:
+
+```sh
+export ANDROID_HOME=/usr/local/lib/android/sdk
+export ANDROID_NDK=$ANDROID_HOME/ndk/25.2.9519653
+```
+
+Note that the value of `ANDROID_HOME` will vary depending on your environment,
+but a typical configuration would be as follows:
+
+- Windows: `C:\\Users\\USERNAME\\AppData\\Local\\Android\\sdk`
+- Linux: `/home/USERNAME/Android/Sdk`
+- macOS: `/Users/USERNAME/Library/Android/sdk`
+
+Then build as follows:
+
+```
+sh build-android.sh ABI -DBUILD_TESTSUITE=OFF
+```
+
+`ABI` should be replaced by `arm64-v8a`, `armeabi-v7a`, `x86`, or `x86_64`.
+
+[wikipedia::md5]: https://en.wikipedia.org/wiki/MD5
+[ietf::rfc1321]: https://www.ietf.org/rfc/rfc1321.txt
+[openssl::md5_init]: https://www.openssl.org/docs/man1.1.1/man3/MD5_Init.html
+[maroontress::lighter]: https://github.com/maroontress/lighter
diff --git a/build-android.sh b/build-android.sh
new file mode 100644
index 0000000..19ad673
--- /dev/null
+++ b/build-android.sh
@@ -0,0 +1,40 @@
+#!/bin/sh
+
+if [ "$#" = 0 ] ; then
+  echo usage: $0 ABI [CMAKE_OPTIONS...]
+  exit 1
+fi
+
+# Environment variables:
+#   ANDROID_NDK (e.g., "$HOME/Library/Android/sdk/ndk/25.2.9519653")
+#   ANDROID_HOME (e.g., "$HOME/Library/Android/sdk")
+
+# ABI:
+#   "x86"
+#   "x86_64"
+#   "arm64-v8a"
+#   "armeabi-v7a"
+
+# Options:
+#   -DCMAKE_INSTALL_PREFIX:PATH="$HOME/android/$ABI"
+#   -DBUILD_TESTSUITE=OFF
+
+ABI=$1
+if [ "$ABI" = "armeabi-v7a" ] ; then
+    EXTRA_ARGS='-DCMAKE_ANDROID_ARM_NEON=ON'
+fi
+shift
+rm -rf "build-$ABI" || exit 1
+cmake -S . -B "build-$ABI" -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_SYSTEM_NAME=Android \
+    -DCMAKE_CROSSCOMPILING_EMULATOR="$PWD/emulator-android.sh" \
+    -DCMAKE_SYSTEM_VERSION="21" \
+    -DCMAKE_ANDROID_ARCH_ABI="$ABI" \
+    -DCMAKE_ANDROID_NDK="$ANDROID_NDK" \
+    $EXTRA_ARGS "$@" || exit 1
+cmake --build "build-$ABI" --config Release -v || exit 1
+if test -f "build-$ABI/testsuite/testsuite" ; then
+    sh emulator-android.sh --adb-push "build-$ABI/testsuite"
+    ctest --test-dir "build-$ABI" -C Release -V || exit 1
+    sh emulator-android.sh --adb-pull "build-$ABI/testsuite"
+fi
diff --git a/emulator-android.sh b/emulator-android.sh
new file mode 100755
index 0000000..dc63d74
--- /dev/null
+++ b/emulator-android.sh
@@ -0,0 +1,53 @@
+#!/bin/sh
+
+# Usage:
+#   emulator-android.sh --adb-push DIR
+#   emulator-android.sh --adb-pull DIR
+#   emulator-android.sh TESTCASE [ARGS...]
+
+ADB="$ANDROID_HOME/platform-tools/adb"
+REMOTE_DIR="/data/local/tmp"
+LOG="log.txt"
+
+setupLog() {
+    echo "---" >> $LOG
+    echo args: "$@" >> $LOG
+    echo pwd: $PWD >> $LOG
+    echo log: >> $LOG
+}
+
+if [ "$1" = "--adb-push" ] ; then
+    cd "$2"
+    setupLog "$@"
+    echo "--adb-push: do nothing" >> $LOG
+    exit
+fi
+if [ "$1" = "--adb-pull" ] ; then
+    cd "$2"
+    setupLog "$@"
+    echo "--adb-pull: do nothing" >> $LOG
+    exit
+fi
+
+setupLog "$@"
+name="$1"
+if [ "${name##*/}" != "testsuite" ] ; then
+    echo unexpected testcase >> $LOG
+    exit 1
+fi
+shift
+if [ "$1" = "--gtest_list_tests" ] ; then
+    echo devices: >> $LOG
+    $ADB devices >> $LOG
+    $ADB push testsuite $REMOTE_DIR/testsuite >> $LOG
+    $ADB shell chmod +x $REMOTE_DIR/testsuite >> $LOG
+fi
+
+n="'"
+args=$n$1$n
+shift
+for i in "$@" ; do
+    args="$args $n$i$n"
+done
+echo $ADB shell "cd $REMOTE_DIR && ./testsuite $args" >> $LOG
+$ADB shell "cd $REMOTE_DIR && ./testsuite $args"
diff --git a/libmimicssl-md5/CMakeLists.txt b/libmimicssl-md5/CMakeLists.txt
new file mode 100644
index 0000000..a6ff9aa
--- /dev/null
+++ b/libmimicssl-md5/CMakeLists.txt
@@ -0,0 +1,40 @@
+set(CMAKE_C_STANDARD 23)
+
+if("${CMAKE_C_COMPILER_ID}" STREQUAL "Clang"
+        OR "${CMAKE_C_COMPILER_ID}" STREQUAL "AppleClang"
+        OR "${CMAKE_C_COMPILER_ID}" STREQUAL "GNU")
+    add_compile_options(-Wall -Wextra -Wpedantic)
+    set(CMAKE_C_FLAGS_DEBUG "-O0 -g")
+    set(CMAKE_C_FLAGS_RELEASE "-O3")
+elseif("${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC")
+    add_compile_options(/W4 /WX)
+endif()
+
+include(GenerateExportHeader)
+
+add_library(mimicssl-md5 STATIC)
+generate_export_header(mimicssl-md5
+    BASE_NAME MD5
+    EXPORT_FILE_NAME ${PROJECT_BINARY_DIR}/md5_export.h)
+target_sources(mimicssl-md5 PRIVATE
+    src/md5.c)
+target_include_directories(mimicssl-md5 PUBLIC
+    include
+    ${PROJECT_BINARY_DIR})
+
+add_library(mimicssl-md5-shared SHARED)
+target_sources(mimicssl-md5-shared PRIVATE
+    src/md5.c)
+target_include_directories(mimicssl-md5-shared PUBLIC
+    include
+    ${PROJECT_BINARY_DIR})
+set_target_properties(mimicssl-md5-shared
+    PROPERTIES OUTPUT_NAME mimicssl-md5)
+
+include(GNUInstallDirs)
+install(TARGETS mimicssl-md5 DESTINATION lib)
+install(TARGETS mimicssl-md5-shared DESTINATION lib)
+install(FILES
+    include/md5.h
+    ${PROJECT_BINARY_DIR}/md5_export.h
+    DESTINATION include/mimicssl)
diff --git a/libmimicssl-md5/include/md5.h b/libmimicssl-md5/include/md5.h
new file mode 100644
index 0000000..315ca21
--- /dev/null
+++ b/libmimicssl-md5/include/md5.h
@@ -0,0 +1,37 @@
+#ifndef md5_H
+#define md5_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "md5_export.h"
+
+#define MD5_LONG uint32_t
+#define MD5_CBLOCK 64
+#define MD5_LBLOCK (MD5_CBLOCK / 4)
+#define MD5_DIGEST_LENGTH 16
+
+struct MD5_Hash {
+    uint32_t data[4];
+};
+
+typedef struct {
+    struct MD5_Hash hash;
+    uint8_t input[MD5_CBLOCK];
+    uint64_t size;
+    uint8_t unused[4];
+} MD5_CTX;
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+int MD5_EXPORT MD5_Init(MD5_CTX *c);
+int MD5_EXPORT MD5_Update(MD5_CTX *c, const void *data, size_t len);
+int MD5_EXPORT MD5_Final(unsigned char *md, MD5_CTX *c);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif
diff --git a/libmimicssl-md5/src/libext1.h b/libmimicssl-md5/src/libext1.h
new file mode 100644
index 0000000..ea27758
--- /dev/null
+++ b/libmimicssl-md5/src/libext1.h
@@ -0,0 +1,20 @@
+#ifndef libext1_H
+#define libext1_H
+
+#include <string.h>
+
+#if defined(__STDC_LIB_EXT1__) || defined(_WIN32)
+#include <stdlib.h>
+static void *
+MEMCPY(void *x, const void *y, size_t z)
+{
+    if (memcpy_s(x, z, y, z) != 0) {
+        abort();
+    }
+    return x;
+}
+#else
+#define MEMCPY(x, y, z) memcpy(x, y, z)
+#endif
+
+#endif
diff --git a/libmimicssl-md5/src/md5.c b/libmimicssl-md5/src/md5.c
new file mode 100644
index 0000000..cadd871
--- /dev/null
+++ b/libmimicssl-md5/src/md5.c
@@ -0,0 +1,234 @@
+#if defined(__STDC_LIB_EXT1__) && (__STDC_LIB_EXT1__ >= 201112L)
+#define __STDC_WANT_LIB_EXT1__ 1
+#endif
+
+#include <stdio.h>
+#include <string.h>
+
+#include "md5.h"
+
+#include "libext1.h"
+
+struct Unit {
+    uint32_t data[16];
+};
+
+struct X {
+    uint32_t k;
+    uint32_t r;
+};
+
+static const struct MD5_Hash ABCD = {
+    .data = {0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476}};
+
+static const uint32_t K_ROUND_1[] = {
+    0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
+    0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
+    0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
+    0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821};
+
+static const struct X X_ROUND_2[] = {
+    {0xf61e2562, 1}, {0xc040b340, 6}, {0x265e5a51, 11}, {0xe9b6c7aa, 0},
+    {0xd62f105d, 5}, {0x2441453, 10}, {0xd8a1e681, 15}, {0xe7d3fbc8, 4},
+    {0x21e1cde6, 9}, {0xc33707d6, 14}, {0xf4d50d87, 3}, {0x455a14ed, 8},
+    {0xa9e3e905, 13}, {0xfcefa3f8, 2}, {0x676f02d9, 7}, {0x8d2a4c8a, 12}};
+static const struct X X_ROUND_3[] = {
+    {0xfffa3942, 5}, {0x8771f681, 8}, {0x6d9d6122, 11}, {0xfde5380c, 14},
+    {0xa4beea44, 1}, {0x4bdecfa9, 4}, {0xf6bb4b60, 7}, {0xbebfbc70, 10},
+    {0x289b7ec6, 13}, {0xeaa127fa, 0}, {0xd4ef3085, 3}, {0x4881d05, 6},
+    {0xd9d4d039, 9}, {0xe6db99e5, 12}, {0x1fa27cf8, 15}, {0xc4ac5665, 2}};
+static const struct X X_ROUND_4[] = {
+    {0xf4292244, 0}, {0x432aff97, 7}, {0xab9423a7, 14}, {0xfc93a039, 5},
+    {0x655b59c3, 12}, {0x8f0ccc92, 3}, {0xffeff47d, 10}, {0x85845dd1, 1},
+    {0x6fa87e4f, 8}, {0xfe2ce6e0, 15}, {0xa3014314, 6}, {0x4e0811a1, 13},
+    {0xf7537e82, 4}, {0xbd3af235, 11}, {0x2ad7d2bb, 2}, {0xeb86d391, 9}};
+
+static const uint32_t S_ROUND_1[] = {7, 12, 17, 22};
+static const uint32_t S_ROUND_2[] = {5, 9, 14, 20};
+static const uint32_t S_ROUND_3[] = {4, 11, 16, 23};
+static const uint32_t S_ROUND_4[] = {6, 10, 15, 21};
+
+static uint32_t f(uint32_t x, uint32_t y, uint32_t z)
+{
+    return ((x & y) | (~x & z));
+}
+
+static uint32_t g(uint32_t x, uint32_t y, uint32_t z)
+{
+    return ((x & z) | (y & ~z));
+}
+
+static uint32_t h(uint32_t x, uint32_t y, uint32_t z)
+{
+    return (x ^ y ^ z);
+}
+
+static uint32_t i(uint32_t x, uint32_t y, uint32_t z)
+{
+    return (y ^ (x | ~z));
+}
+
+static uint32_t rotate(uint32_t x, uint32_t s)
+{
+    return (x << s) | (x >> (32 - s));
+}
+
+static void roundUnit(struct MD5_Hash *hash, const struct Unit *unit)
+{
+    const uint32_t *const m = unit->data;
+    uint32_t *const hashData = hash->data;
+    uint32_t a0 = hashData[0];
+    uint32_t b0 = hashData[1];
+    uint32_t c0 = hashData[2];
+    uint32_t d0 = hashData[3];
+
+    do {
+        const uint32_t *const s = S_ROUND_1;
+        const uint32_t *k = K_ROUND_1;
+        const uint32_t *z = m;
+        for (uint32_t j = 0; j < 4; ++j) {
+            a0 = rotate(a0 + f(b0, c0, d0) + z[0] + k[0], s[0]) + b0;
+            d0 = rotate(d0 + f(a0, b0, c0) + z[1] + k[1], s[1]) + a0;
+            c0 = rotate(c0 + f(d0, a0, b0) + z[2] + k[2], s[2]) + d0;
+            b0 = rotate(b0 + f(c0, d0, a0) + z[3] + k[3], s[3]) + c0;
+            z += 4;
+            k += 4;
+        }
+    } while (0);
+    do {
+        const uint32_t *const s = S_ROUND_2;
+        const struct X *x = X_ROUND_2;
+        for (uint32_t j = 0; j < 4; ++j) {
+            a0 = rotate(a0 + g(b0, c0, d0) + m[x[0].r] + x[0].k, s[0]) + b0;
+            d0 = rotate(d0 + g(a0, b0, c0) + m[x[1].r] + x[1].k, s[1]) + a0;
+            c0 = rotate(c0 + g(d0, a0, b0) + m[x[2].r] + x[2].k, s[2]) + d0;
+            b0 = rotate(b0 + g(c0, d0, a0) + m[x[3].r] + x[3].k, s[3]) + c0;
+            x += 4;
+        }
+    } while (0);
+    do {
+        const uint32_t *const s = S_ROUND_3;
+        const struct X *x = X_ROUND_3;
+        for (uint32_t j = 0; j < 4; ++j) {
+            a0 = rotate(a0 + h(b0, c0, d0) + m[x[0].r] + x[0].k, s[0]) + b0;
+            d0 = rotate(d0 + h(a0, b0, c0) + m[x[1].r] + x[1].k, s[1]) + a0;
+            c0 = rotate(c0 + h(d0, a0, b0) + m[x[2].r] + x[2].k, s[2]) + d0;
+            b0 = rotate(b0 + h(c0, d0, a0) + m[x[3].r] + x[3].k, s[3]) + c0;
+            x += 4;
+        }
+    } while (0);
+    do {
+        const uint32_t *const s = S_ROUND_4;
+        const struct X *x = X_ROUND_4;
+        for (uint32_t j = 0; j < 4; ++j) {
+            a0 = rotate(a0 + i(b0, c0, d0) + m[x[0].r] + x[0].k, s[0]) + b0;
+            d0 = rotate(d0 + i(a0, b0, c0) + m[x[1].r] + x[1].k, s[1]) + a0;
+            c0 = rotate(c0 + i(d0, a0, b0) + m[x[2].r] + x[2].k, s[2]) + d0;
+            b0 = rotate(b0 + i(c0, d0, a0) + m[x[3].r] + x[3].k, s[3]) + c0;
+            x += 4;
+        }
+    } while (0);
+    hashData[0] += a0;
+    hashData[1] += b0;
+    hashData[2] += c0;
+    hashData[3] += d0;
+}
+
+static uint32_t toLE32(const uint8_t *m)
+{
+    return (uint32_t)m[0] | (uint32_t)m[1] << 8 | (uint32_t)m[2] << 16
+        | (uint32_t)m[3] << 24;
+}
+
+int MD5_Init(MD5_CTX *c)
+{
+    c->size = 0;
+    c->hash = ABCD;
+    return 1;
+}
+
+int MD5_Update(MD5_CTX *c, const void *data, size_t len)
+{
+    struct Unit unit;
+    uint32_t *unitData = unit.data;
+    const uint8_t *source = data;
+
+    size_t remaining = c->size % 64;
+    if (remaining > 0) {
+        size_t size = 64 - remaining;
+        if (len < size) {
+            MEMCPY(c->input + remaining, data, len);
+            c->size += len;
+            return 0;
+        }
+        MEMCPY(c->input + remaining, data, size);
+        const uint8_t *m = c->input;
+        for (uint32_t j = 0; j < 16; ++j) {
+            unitData[j] = toLE32(m);
+            m += 4;
+        }
+        roundUnit(&c->hash, &unit);
+        c->size += size;
+        len -= size;
+        source += size;
+    }
+
+    while (len >= 64) {
+        for (uint32_t j = 0; j < 16; ++j) {
+            unitData[j] = toLE32(source);
+            source += 4;
+        }
+        roundUnit(&c->hash, &unit);
+        c->size += 64;
+        len -= 64;
+    }
+    if (len > 0) {
+        MEMCPY(c->input, source, len);
+        c->size += len;
+    }
+    return 1;
+}
+
+int MD5_Final(unsigned char *md, MD5_CTX *c)
+{
+    uint64_t finalSize = c->size;
+    do {
+        uint8_t padding[64];
+        uint32_t remainder = finalSize % 64;
+        uint32_t length = (remainder < 56)
+            ? 56 - remainder
+            : (56 + 64) - remainder;
+        padding[0] = 0x80;
+        for (uint32_t k = 1; k < length; ++k) {
+            padding[k] = 0;
+        }
+        MD5_Update(c, padding, length);
+    } while (0);
+    do {
+        uint32_t lowerSize = (uint32_t)(finalSize << 3);
+        uint32_t upperSize = (uint32_t)(finalSize >> 29);
+        const uint32_t sizeArray[] = {lowerSize, upperSize};
+        uint8_t sizeData[8];
+        uint8_t *d = sizeData;
+        for (uint32_t k = 0; k < 2; ++k) {
+            uint32_t size = sizeArray[k];
+            d[0] = (uint8_t)size;
+            d[1] = (uint8_t)(size >> 8);
+            d[2] = (uint8_t)(size >> 16);
+            d[3] = (uint8_t)(size >> 24);
+            d += 4;
+        }
+        MD5_Update(c, sizeData, sizeof(sizeData));
+    } while (0);
+
+    const uint32_t *hashData = c->hash.data;
+    for (uint32_t k = 0; k < 4; ++k) {
+        uint32_t h = hashData[k];
+        md[0] = (uint8_t)h;
+        md[1] = (uint8_t)(h >> 8);
+        md[2] = (uint8_t)(h >> 16);
+        md[3] = (uint8_t)(h >> 24);
+        md += 4;
+    }
+    return 1;
+}
diff --git a/lighter b/lighter
new file mode 160000
index 0000000..f20f196
--- /dev/null
+++ b/lighter
@@ -0,0 +1 @@
+Subproject commit f20f19649dfdadadcb004b91dcc073efece13d0d
diff --git a/mimicssl-md5-cli/CMakeLists.txt b/mimicssl-md5-cli/CMakeLists.txt
new file mode 100644
index 0000000..d052314
--- /dev/null
+++ b/mimicssl-md5-cli/CMakeLists.txt
@@ -0,0 +1,7 @@
+set(CMAKE_C_STANDARD 23)
+
+add_executable(mimicssl-md5-cli main.c)
+
+target_include_directories(mimicssl-md5-cli PRIVATE mimicssl-md5)
+
+target_link_libraries(mimicssl-md5-cli mimicssl-md5)
diff --git a/mimicssl-md5-cli/main.c b/mimicssl-md5-cli/main.c
new file mode 100644
index 0000000..a4c7be9
--- /dev/null
+++ b/mimicssl-md5-cli/main.c
@@ -0,0 +1,44 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "md5.h"
+
+static void
+printHash(const uint8_t *p)
+{
+    for (unsigned int i = 0; i < 16; ++i) {
+        printf("%02x", p[i]);
+    }
+    printf("\n");
+}
+
+int
+main(int ac, char **av)
+{
+    if (ac < 2) {
+        fprintf(stderr, "usage: %s FILE\n", av[0]);
+        exit(1);
+    }
+    FILE *file = fopen(av[1], "rb");
+    if (file == NULL) {
+        fprintf(stderr, "file not found\n");
+        exit(1);
+    }
+    MD5_CTX ctx;
+    uint8_t md[16];
+    char buffer[1024];
+
+    MD5_Init(&ctx);
+    for (;;) {
+        size_t size = fread(buffer, 1, sizeof(buffer), file);
+        if (size == 0) {
+            break;
+        }
+        MD5_Update(&ctx, buffer, size);
+    }
+    MD5_Final(md, &ctx);
+
+    printHash(md);
+    return 0;
+}
diff --git a/testsuite/CMakeLists.txt b/testsuite/CMakeLists.txt
new file mode 100644
index 0000000..671f53a
--- /dev/null
+++ b/testsuite/CMakeLists.txt
@@ -0,0 +1,14 @@
+set(CMAKE_CXX_STANDARD 23)
+
+enable_testing()
+
+add_executable(testsuite
+    main.cxx expect.hxx expect_fallback.hxx)
+
+target_include_directories(testsuite PRIVATE
+    mimicssl-md5 ${CMAKE_SOURCE_DIR}/lighter/include)
+
+target_link_libraries(testsuite mimicssl-md5)
+
+include(GoogleTest)
+gtest_discover_tests(testsuite)
diff --git a/testsuite/expect.hxx b/testsuite/expect.hxx
new file mode 100644
index 0000000..35851b3
--- /dev/null
+++ b/testsuite/expect.hxx
@@ -0,0 +1,24 @@
+#ifndef expect_HXX
+#define expect_HXX
+
+#include <sstream>
+
+#if __has_include(<source_location>)
+#include <source_location>
+
+#include "maroontress/lighter/Flint.hxx"
+
+#define expect(x) maroontress::lighter::Flint {(x), #x, [](auto r) { \
+        const auto& w = std::source_location::current(); \
+        std::ostringstream out; \
+        out \
+            << w.file_name() << ":" << w.line() << ": error:" << std::endl \
+            << "  Expected: " << r.getExpected() << std::endl \
+            << "  Actual:   " << r.getActual() << std::endl; \
+        throw std::runtime_error(out.str()); \
+    }}
+#else
+#include "expect_fallback.hxx"
+#endif
+
+#endif
diff --git a/testsuite/expect_fallback.hxx b/testsuite/expect_fallback.hxx
new file mode 100644
index 0000000..19c0b6c
--- /dev/null
+++ b/testsuite/expect_fallback.hxx
@@ -0,0 +1,16 @@
+#ifndef expect_fallback_HXX
+#define expect_fallback_HXX
+
+#include "maroontress/lighter/Flint.hxx"
+
+#define expect(x) maroontress::lighter::Flint {(x), #x, [](auto r) { \
+        auto fileName = __FILE__; \
+        auto line = __LINE__; \
+        std::ostringstream out; \
+        out << fileName << ":" << line << ": error:" << std::endl \
+            << "  Expected: " << r.getExpected() << std::endl \
+            << "  Actual:   " << r.getActual() << std::endl; \
+        throw std::runtime_error(out.str()); \
+    }}
+
+#endif
diff --git a/testsuite/main.cxx b/testsuite/main.cxx
new file mode 100644
index 0000000..e4b71c2
--- /dev/null
+++ b/testsuite/main.cxx
@@ -0,0 +1,213 @@
+#include <array>
+#include <bit>
+#include <cstdint>
+#include <cstring>
+#include <functional>
+#include <iostream>
+#include <map>
+#include <string>
+
+#include "md5.h"
+
+#include "expect.hxx"
+
+class Driver final {
+private:
+    std::map<std::string, std::function<void()>> map;
+    bool list = false;
+    std::optional<std::string> name;
+
+public:
+    Driver(const char* const* args) {
+        for (auto* a = args; *a != nullptr; ++a) {
+            if (std::strcmp(*a, "--gtest_list_tests") == 0) {
+                list = true;
+                return;
+            }
+        }
+        for (auto* a = args; *a != nullptr; ++a) {
+            auto o = std::string {*a};
+            auto prefix = std::string {"--gtest_filter=main."};
+            if (o.starts_with(prefix)) {
+                name = std::make_optional(o.substr(prefix.length()));
+                return;
+            }
+        }
+    }
+
+    void add(const std::string& name, const std::function<void()>& testcase) {
+        map[name] = testcase;
+    }
+
+    int run() const {
+        if (list) {
+            std::cout << "main.\n";
+            for (auto i = map.cbegin(); i != map.cend(); ++i) {
+                auto [name, testcase] = *i;
+                std::cout << "  " << name << "\n";
+            }
+            return 0;
+        }
+        if (name.has_value()) {
+            std::string n = name.value();
+            auto testcase = map.at(n);
+            try {
+                testcase();
+                std::cout << n << ": succeeded\n";
+            } catch (std::runtime_error& e) {
+                std::cout << n << ": failed\n";
+                std::cout << "  " << e.what();
+                return 1;
+            }
+            return 0;
+        }
+        auto count = 0;
+        for (auto i = map.cbegin(); i != map.cend(); ++i) {
+            auto [name, testcase] = *i;
+            try {
+                testcase();
+                std::cout << name << ": succeeded\n";
+            } catch (std::runtime_error& e) {
+                std::cout << name << ": failed\n";
+                std::cout << "  " << e.what();
+                ++count;
+            }
+        }
+        if (count == 0) {
+            std::cout << "all tests passed\n";
+            return 0;
+        }
+        std::cout << count << " test(s) failed.\n";
+        return 1;
+    }
+};
+
+namespace maroontress::lighter {
+    template <>
+    std::string toString(std::uint8_t b) {
+        auto v = (uint32_t)b;
+        std::ostringstream out;
+        out << std::dec << v << " (0x" << std::hex << v << ")";
+        return out.str();
+    }
+}
+
+static auto
+toArray(const std::string& m) -> std::array<std::uint8_t, 16>
+{
+    std::uint8_t array[16];
+
+    if (m.length() != 32) {
+        throw std::runtime_error("invalid length");
+    }
+    for (auto k = 0; k < 16; ++k) {
+        auto p = m.substr(k * 2, 2);
+        array[k] = (std::uint8_t)std::stoull(p, nullptr, 16);
+    }
+    return std::to_array(array);
+}
+
+static auto
+withString(const std::string& m, const std::array<uint8_t, 16>& expected)
+    -> void
+{
+    MD5_CTX ctx;
+    uint8_t actual[16];
+
+    MD5_Init(&ctx);
+    MD5_Update(&ctx, m.c_str(), m.length());
+    MD5_Final(actual, &ctx);
+    for (auto k = 0; k < 16; ++k) {
+        expect(actual[k]) == expected[k];
+    }
+}
+
+int
+main(int ac, char** av) {
+    auto driver = Driver {av};
+    driver.add("endian", [] {
+        expect(std::endian::native) == std::endian::little;
+    });
+    driver.add("empty", [] {
+        MD5_CTX ctx;
+        uint8_t actual[16];
+
+        MD5_Init(&ctx);
+        MD5_Final(actual, &ctx);
+
+        // MD5 ("") = d41d8cd98f00b204e9800998ecf8427e
+        auto expected = toArray("d41d8cd98f00b204e9800998ecf8427e");
+        for (auto k = 0; k < 16; ++k) {
+            expect(actual[k]) == expected[k];
+        }
+    });
+    driver.add("a", [] {
+        // MD5 ("a") = 0cc175b9c0f1b6a831c399e269772661
+        auto expected = toArray("0cc175b9c0f1b6a831c399e269772661");
+        withString("a", expected);
+    });
+    driver.add("abc", [] {
+        // MD5 ("abc") = 900150983cd24fb0d6963f7d28e17f72
+        auto expected = toArray("900150983cd24fb0d6963f7d28e17f72");
+        withString("abc", expected);
+    });
+    driver.add("message digest", [] {
+        // MD5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0
+        auto expected = toArray("f96b697d7cb7938d525a2f31aaf161d0");
+        withString("message digest", expected);
+    });
+    driver.add("a-z", [] {
+        // MD5 ("abcdefghijklmnopqrstuvwxyz")
+        // = c3fcd3d76192e4007dfb496cca67e13b
+        auto expected = toArray("c3fcd3d76192e4007dfb496cca67e13b");
+        withString("abcdefghijklmnopqrstuvwxyz", expected);
+    });
+    driver.add("A-Za-z0-9", [] {
+        // MD5 ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
+        // 0123456789") = d174ab98d277d9f5a5611c2c9f419d9f
+        auto expected = toArray("d174ab98d277d9f5a5611c2c9f419d9f");
+        withString("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+            "0123456789", expected);
+    });
+    driver.add("1-90-9...0-90", [] {
+        // MD5 ("12345678901234567890123456789012345678901234567890123456789
+        // 012345678901234567890") = 57edf4a22be3c955ac49da2e2107b67a
+        auto expected = toArray("57edf4a22be3c955ac49da2e2107b67a");
+        withString("1234567890123456789012345678901234567890123456789"
+            "0123456789012345678901234567890", expected);
+    });
+
+    driver.add("process one byte at a time", [] {
+        MD5_CTX ctx;
+        uint8_t actual[16];
+        uint8_t expected[16];
+
+        MD5_Init(&ctx);
+        std::string m {
+            "Alice was beginning to get very tired of sitting by her sister "
+            "on the bank, and of having nothing to do: once or twice she had "
+            "peeped into the book her sister was reading, but it had no "
+            "pictures or conversations in it, and where is the use of a "
+            "book, thought Alice, without pictures or conversations? So she "
+            "was considering in her own mind, (as well as she could, for the "
+            "hot day made her feel very sleepy and stupid,) whether the "
+            "pleasure of making a daisy-chain would be worth the trouble of "
+            "getting up and picking the daisies, when suddenly a white "
+            "rabbit with pink eyes ran close by her."};
+        std::size_t length = m.length();
+        const char* top = m.c_str();
+        for (auto k = 0; k < length; ++k) {
+            MD5_Update(&ctx, top + k, 1);
+        }
+        MD5_Final(actual, &ctx);
+
+        MD5_Init(&ctx);
+        MD5_Update(&ctx, m.c_str(), length);
+        MD5_Final(expected, &ctx);
+
+        for (auto k = 0; k < 16; ++k) {
+            expect(actual[k]) == expected[k];
+        }
+    });
+    return driver.run();
+}