diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8d62cf1a..9f7d2bcf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -249,6 +249,8 @@ list (
     hash/murmur/murmur2.hpp
     hash/murmur/murmur3.cpp
     hash/murmur/murmur3.hpp
+    hash/siphash.cpp
+    hash/siphash.hpp
     hash/wang.hpp
     hash/xxhash.cpp
     hash/xxhash.hpp
@@ -469,6 +471,7 @@ if (TESTS)
         hash/fasthash
         hash/fnv1a
         hash/murmur
+        hash/siphash
         hash/xxhash
         hton
         introspection
diff --git a/hash/siphash.cpp b/hash/siphash.cpp
new file mode 100644
index 00000000..c505b637
--- /dev/null
+++ b/hash/siphash.cpp
@@ -0,0 +1,123 @@
+/*
+ * 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.
+ *
+ * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "siphash.hpp"
+
+#include "../bitwise.hpp"
+#include "../debug.hpp"
+#include "../endian.hpp"
+
+using util::hash::siphash;
+
+
+///////////////////////////////////////////////////////////////////////////////
+static constexpr
+uint64_t INITIALISERS[4] = {
+    0x736f6d6570736575,
+    0x646f72616e646f6d,
+    0x6c7967656e657261,
+    0x7465646279746573,
+};
+
+
+///////////////////////////////////////////////////////////////////////////////
+void
+round (uint64_t v[4])
+{
+    using util::rotatel;
+
+    v[0] += v[1];              v[2] += v[3];
+    v[1] = rotatel (v[1], 13); v[3] = rotatel (v[3], 16);
+    v[1] ^= v[0];              v[3] ^= v[2];
+    v[0] = rotatel (v[0], 32);
+
+    v[2] += v[1];               v[0] += v[3];
+    v[1]  = rotatel (v[1], 17); v[3] = rotatel (v[3], 21);
+    v[1] ^= v[2];               v[3] ^= v[0];
+    v[2]  = rotatel (v[2], 32);
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename ValueT>
+ValueT
+readle (const void *ptr)
+{
+    return util::htol (*reinterpret_cast<const ValueT*> (ptr));
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <int C, int D>
+siphash<C,D>::siphash (std::array<uint64_t,2> _key) noexcept:
+    m_key (_key)
+{ ; }
+
+
+//-----------------------------------------------------------------------------
+template <int C, int D>
+typename siphash<C,D>::digest_t
+siphash<C,D>::operator() (util::view<const uint8_t*> data) const noexcept
+{
+    // init
+    uint64_t state[4] = {
+        m_key[0] ^ INITIALISERS[0],
+        m_key[1] ^ INITIALISERS[1],
+        m_key[0] ^ INITIALISERS[2],
+        m_key[1] ^ INITIALISERS[3],
+    };
+
+    // update
+    auto cursor = data.begin ();
+    for ( ; data.end () - cursor > 8; cursor += sizeof (uint64_t)) {
+        auto word = readle<uint64_t> (cursor);
+
+        state[3] ^= word;
+        for (int c = 0; c < C; ++c)
+            round (state);
+        state[0] ^= word;
+    }
+
+    // drain
+    union {
+        uint64_t d64 = 0;
+        uint8_t d08[8];
+    } accum;
+
+    if (cursor != data.cend ()) {
+        std::copy (cursor, data.cend (), std::begin (accum.d08));
+        cursor = data.cend ();
+    }
+
+    CHECK_EQ (cursor, data.cend ());
+    // append the length
+    accum.d08[7] = data.size ();
+
+    state[3] ^= accum.d64;
+    for (int c = 0; c < C; ++c)
+        round (state);
+    state[0] ^= accum.d64;
+
+    // finalisation
+    state[2] ^= 0xff;
+    for (int d = 0; d < D; ++d)
+        round (state);
+
+    return state[0] ^ state[1] ^ state[2] ^ state[3];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+template class util::hash::siphash<2,4>;
diff --git a/hash/siphash.hpp b/hash/siphash.hpp
new file mode 100644
index 00000000..18e1b7de
--- /dev/null
+++ b/hash/siphash.hpp
@@ -0,0 +1,43 @@
+/*
+ * 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.
+ *
+ * Copyright 2016-2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef CRUFT_UTIL_HASH_SIPHASH_HPP
+#define CRUFT_UTIL_HASH_SIPHASH_HPP
+
+#include "../view.hpp"
+
+#include <cstdint>
+#include <type_traits>
+
+namespace util::hash {
+    template <int CompressionsV, int FinalisationsV>
+    class siphash {
+    public:
+        using digest_t = std::uint64_t;
+
+        static constexpr auto compression_rounds = CompressionsV;
+        static constexpr auto finalisation_rounds = FinalisationsV;
+
+        siphash (std::array<uint64_t,2>) noexcept;
+
+        digest_t operator() (util::view<const std::uint8_t*> data) const noexcept;
+
+    private:
+        std::array<uint64_t,2> m_key;
+    };
+};
+
+#endif
diff --git a/test/hash/siphash.cpp b/test/hash/siphash.cpp
new file mode 100644
index 00000000..5f41ef83
--- /dev/null
+++ b/test/hash/siphash.cpp
@@ -0,0 +1,35 @@
+
+#include "tap.hpp"
+
+#include "hash/siphash.hpp"
+
+
+///////////////////////////////////////////////////////////////////////////////
+static const struct {
+    std::array<uint64_t,2> key;
+    std::vector<uint8_t> data;
+    uint64_t digest;
+    const char *message;
+} TESTS[] = {
+    {
+        { 0x0706050403020100, 0x0f0e0d0c0b0a0908 },
+        { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+          0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e
+        },
+        0xa129ca6149be45e5,
+        "byte sequence",
+    }
+};
+
+
+///////////////////////////////////////////////////////////////////////////////
+int
+main ()
+{
+    util::TAP::logger tap;
+
+    for (const auto &t: TESTS) {
+        util::hash::siphash<2,4> h (t.key);
+        tap.expect_eq (h (t.data), t.digest, "%s", t.message);
+    }
+}
\ No newline at end of file