--- /dev/null
+#ifndef CCAN_SIPHASH_H_
+#define CCAN_SIPHASH_H_
+
+/* Licensed under GPL v2+ - see LICENSE file for details */
+/* Written in 2013 by Ulrik Sverdrup */
+
+#include <stdint.h>
+#include <stddef.h>
+
+/**
+ * siphash - a keyed hash function
+ *
+ * SipHash-c-d, where `c` is the number of rounds per message chunk
+ * and `d` the number of finalization rounds,
+ * "is a family of pseudorandom functions optimized for speed on short
+ * messages"
+ *
+ * Implemented from the paper https://131002.net/siphash/
+ * The designers recommend using SipHash-2-4 or SipHash-4-8
+ *
+ * SipHash-c-d uses a 16-byte key.
+ * To defend against hash-flooding, the application needs to use
+ * a new random key regularly.
+ *
+ * The designers of SipHash claim it is cryptographically strong
+ * to use as MAC with secret key but _not_collision_resistant_.
+ *
+ * Returns one 64-bit word as the hash function result.
+ *
+ * Example:
+ * // Outputs "cf2794e0277187b7"
+ * #include <stdio.h>
+ * #include <ccan/siphash/siphash.h>
+ *
+ * int main(void)
+ * {
+ * unsigned char t_key[16] =
+ * {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
+ * unsigned char data[4] = "\0\1\2\3";
+ * uint64_t hash = siphash_2_4(data, sizeof(data), t_key);
+ * printf("%llx\n", (unsigned long long)hash);
+ *
+ * return 0;
+ * }
+ *
+ */
+uint64_t siphash_2_4(const void *in, size_t len, const unsigned char key[16]);
+
+#endif /* CCAN_SIPHASH_H_ */
+