diff --git a/src/openvpn/siphash.h b/src/openvpn/siphash.h
new file mode 100644
index 0000000..d26ee36
--- /dev/null
+++ b/src/openvpn/siphash.h
@@ -0,0 +1,31 @@
+/*
+ * SipHash reference C implementation
+ *
+ * Copyright (c) 2012-2021 Jean-Philippe Aumasson
+ * <jeanphilippe.aumasson@gmail.com>
+ * Copyright (c) 2012-2014 Daniel J. Bernstein <djb@cr.yp.to>
+ *
+ * To the extent possible under law, the author(s) have dedicated all copyright
+ * and related and neighboring rights to this software to the public domain
+ * worldwide. This software is distributed without any warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication along
+ * with
+ * this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#ifndef SIPHASH_H
+#define SIPHASH_H
+
+#include <inttypes.h>
+#include <string.h>
+
+int siphash(const void *in, size_t inlen, const void *k, uint8_t *out,
+            size_t outlen);
+
+/* siphash always uses 128-bit keys */
+#define SIPHASH_KEY_SIZE    16
+#define SIPHASH_HASH_SIZE   16
+
+#endif
diff --git a/src/openvpn/siphash_reference.c b/src/openvpn/siphash_reference.c
new file mode 100644
index 0000000..35af707
--- /dev/null
+++ b/src/openvpn/siphash_reference.c
@@ -0,0 +1,223 @@
+/*
+ * SipHash reference C implementation
+ *
+ * Copyright 2012-2024 JP Aumasson
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+/* Note:  the reference implementation is also available under CC0 license
+ * (dual licensed) we included the MIT license here since it is shorter */
+
+ #include "siphash.h"
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* default: SipHash-2-4 */
+#ifndef cROUNDS
+#define cROUNDS 2
+#endif
+#ifndef dROUNDS
+#define dROUNDS 4
+#endif
+
+#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
+
+#define U32TO8_LE(p, v)                                                        \
+    (p)[0] = (uint8_t)((v));                                                   \
+    (p)[1] = (uint8_t)((v) >> 8);                                              \
+    (p)[2] = (uint8_t)((v) >> 16);                                             \
+    (p)[3] = (uint8_t)((v) >> 24);
+
+#define U64TO8_LE(p, v)                                                        \
+    U32TO8_LE((p), (uint32_t)((v)));                                           \
+    U32TO8_LE((p) + 4, (uint32_t)((v) >> 32));
+
+#define U8TO64_LE(p)                                                           \
+    (((uint64_t)((p)[0])) | ((uint64_t)((p)[1]) << 8)                          \
+     |((uint64_t)((p)[2]) << 16) | ((uint64_t)((p)[3]) << 24)                   \
+     |((uint64_t)((p)[4]) << 32) | ((uint64_t)((p)[5]) << 40)                   \
+     |((uint64_t)((p)[6]) << 48) | ((uint64_t)((p)[7]) << 56))
+
+#define SIPROUND                                                               \
+    do {                                                                       \
+        v0 += v1;                                                              \
+        v1 = ROTL(v1, 13);                                                     \
+        v1 ^= v0;                                                              \
+        v0 = ROTL(v0, 32);                                                     \
+        v2 += v3;                                                              \
+        v3 = ROTL(v3, 16);                                                     \
+        v3 ^= v2;                                                              \
+        v0 += v3;                                                              \
+        v3 = ROTL(v3, 21);                                                     \
+        v3 ^= v0;                                                              \
+        v2 += v1;                                                              \
+        v1 = ROTL(v1, 17);                                                     \
+        v1 ^= v2;                                                              \
+        v2 = ROTL(v2, 32);                                                     \
+    } while (0)
+
+#ifdef DEBUG_SIPHASH
+#include <stdio.h>
+
+#define TRACE                                                                  \
+    do {                                                                       \
+        printf("(%3zu) v0 %016" PRIx64 "\n", inlen, v0);                       \
+        printf("(%3zu) v1 %016" PRIx64 "\n", inlen, v1);                       \
+        printf("(%3zu) v2 %016" PRIx64 "\n", inlen, v2);                       \
+        printf("(%3zu) v3 %016" PRIx64 "\n", inlen, v3);                       \
+    } while (0)
+#else  /* ifdef DEBUG_SIPHASH */
+#define TRACE
+#endif
+
+/*
+ *  Computes a SipHash value
+ * in: pointer to input data (read-only)
+ *  inlen: input data length in bytes (any size_t value)
+ * k: pointer to the key data (read-only), must be 16 bytes
+ * out: pointer to output data (write-only), outlen bytes must be allocated
+ *  outlen: length of the output in bytes, must be 8 or 16
+ */
+int
+siphash(const void *in, const size_t inlen, const void *k, uint8_t *out,
+        const size_t outlen)
+{
+
+    const unsigned char *ni = (const unsigned char *)in;
+    const unsigned char *kk = (const unsigned char *)k;
+
+    assert((outlen == 8) || (outlen == 16));
+    uint64_t v0 = UINT64_C(0x736f6d6570736575);
+    uint64_t v1 = UINT64_C(0x646f72616e646f6d);
+    uint64_t v2 = UINT64_C(0x6c7967656e657261);
+    uint64_t v3 = UINT64_C(0x7465646279746573);
+    uint64_t k0 = U8TO64_LE(kk);
+    uint64_t k1 = U8TO64_LE(kk + 8);
+    uint64_t m;
+    int i;
+    const unsigned char *end = ni + inlen - (inlen % sizeof(uint64_t));
+    const int left = inlen & 7;
+    uint64_t b = ((uint64_t)inlen) << 56;
+    v3 ^= k1;
+    v2 ^= k0;
+    v1 ^= k1;
+    v0 ^= k0;
+
+    if (outlen == 16)
+    {
+        v1 ^= 0xee;
+    }
+
+    for (; ni != end; ni += 8)
+    {
+        m = U8TO64_LE(ni);
+        v3 ^= m;
+
+        TRACE;
+        for (i = 0; i < cROUNDS; ++i)
+        {
+            SIPROUND;
+        }
+
+        v0 ^= m;
+    }
+
+    switch (left)
+    {
+        case 7:
+            b |= ((uint64_t)ni[6]) << 48;
+
+        /* FALLTHRU */
+        case 6:
+            b |= ((uint64_t)ni[5]) << 40;
+
+        /* FALLTHRU */
+        case 5:
+            b |= ((uint64_t)ni[4]) << 32;
+
+        /* FALLTHRU */
+        case 4:
+            b |= ((uint64_t)ni[3]) << 24;
+
+        /* FALLTHRU */
+        case 3:
+            b |= ((uint64_t)ni[2]) << 16;
+
+        /* FALLTHRU */
+        case 2:
+            b |= ((uint64_t)ni[1]) << 8;
+
+        /* FALLTHRU */
+        case 1:
+            b |= ((uint64_t)ni[0]);
+            break;
+
+        case 0:
+            break;
+    }
+
+    v3 ^= b;
+
+    TRACE;
+    for (i = 0; i < cROUNDS; ++i)
+    {
+        SIPROUND;
+    }
+
+    v0 ^= b;
+
+    if (outlen == 16)
+    {
+        v2 ^= 0xee;
+    }
+    else
+    {
+        v2 ^= 0xff;
+    }
+
+    TRACE;
+    for (i = 0; i < dROUNDS; ++i)
+    {
+        SIPROUND;
+    }
+
+    b = v0 ^ v1 ^ v2 ^ v3;
+    U64TO8_LE(out, b);
+
+    if (outlen == 8)
+    {
+        return 0;
+    }
+
+    v1 ^= 0xdd;
+
+    TRACE;
+    for (i = 0; i < dROUNDS; ++i)
+    {
+        SIPROUND;
+    }
+
+    b = v0 ^ v1 ^ v2 ^ v3;
+    U64TO8_LE(out + 8, b);
+
+    return 0;
+}
