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diff --git a/src/service/setu/ibf.h b/src/service/setu/ibf.h
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+/*
+      This file is part of GNUnet
+      Copyright (C) 2012 GNUnet e.V.
+
+      GNUnet is free software: you can redistribute it and/or modify it
+      under the terms of the GNU Affero General Public License as published
+      by the Free Software Foundation, either version 3 of the License,
+      or (at your option) any later version.
+
+      GNUnet is distributed in the hope that it will be useful, but
+      WITHOUT ANY WARRANTY; without even the implied warranty of
+      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+      Affero General Public License for more details.
+
+      You should have received a copy of the GNU Affero General Public License
+      along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+
+/**
+ * @file set/ibf.h
+ * @brief invertible bloom filter
+ * @author Florian Dold
+ * @author Elias Summermatter
+ */
+
+#ifndef GNUNET_CONSENSUS_IBF_H
+#define GNUNET_CONSENSUS_IBF_H
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+
+/**
+ * Keys that can be inserted into and removed from an IBF.
+ */
+struct IBF_Key
+{
+  uint64_t key_val;
+};
+
+
+/**
+ * Hash of an IBF key.
+ */
+struct IBF_KeyHash
+{
+  uint32_t key_hash_val;
+};
+
+
+/**
+ * Type of the count field of IBF buckets.
+ */
+struct IBF_Count
+{
+  int64_t count_val;
+};
+
+
+/**
+ * Size of one ibf bucket in bytes
+ */
+#define IBF_BUCKET_SIZE (sizeof(struct IBF_Count) + sizeof(struct IBF_Key)   \
+                         + sizeof(struct IBF_KeyHash))
+
+
+/**
+ * Invertible bloom filter (IBF).
+ *
+ * An IBF is a counting bloom filter that has the ability to restore
+ * the hashes of its stored elements with high probability.
+ */
+struct InvertibleBloomFilter
+{
+  /**
+   * How many cells does this IBF have?
+   */
+  uint32_t size;
+
+  /**
+   * In how many cells do we hash one element?
+   * Usually 4 or 3.
+   */
+  uint8_t hash_num;
+
+  /**
+ * If an IBF is decoded this count stores how many
+ * elements are on the local site. This is used
+ * to estimate the set difference on a site
+ */
+  int local_decoded_count;
+
+  /**
+ * If an IBF is decoded this count stores how many
+ * elements are on the remote site. This is used
+ * to estimate the set difference on a site
+ */
+  int remote_decoded_count;
+
+  /**
+   * Xor sums of the elements' keys, used to identify the elements.
+   * Array of 'size' elements.
+   */
+  struct IBF_Key *key_sum;
+
+  /**
+   * Xor sums of the hashes of the keys of inserted elements.
+   * Array of 'size' elements.
+   */
+  struct IBF_KeyHash *key_hash_sum;
+
+  /**
+   * How many times has a bucket been hit?
+   * Can be negative, as a result of IBF subtraction.
+   * Array of 'size' elements.
+   */
+  struct IBF_Count *count;
+};
+
+
+/**
+ * Write buckets from an ibf to a buffer.
+ * Exactly (IBF_BUCKET_SIZE*ibf->size) bytes are written to buf.
+ *
+ * @param ibf the ibf to write
+ * @param start with which bucket to start
+ * @param count how many buckets to write
+ * @param buf buffer to write the data to
+ */
+void
+ibf_write_slice (const struct InvertibleBloomFilter *ibf,
+                 uint32_t start,
+                 uint64_t count,
+                 void *buf,
+                 uint8_t counter_max_length);
+
+
+/**
+ * Read buckets from a buffer into an ibf.
+ *
+ * @param buf pointer to the buffer to read from
+ * @param start which bucket to start at
+ * @param count how many buckets to read
+ * @param ibf the ibf to write to
+ */
+void
+ibf_read_slice (const void *buf,
+                uint32_t start,
+                uint64_t count,
+                struct InvertibleBloomFilter *ibf,
+                uint8_t counter_max_length);
+
+
+/**
+ * Create a key from a hashcode.
+ *
+ * @param hash the hashcode
+ * @return a key
+ */
+struct IBF_Key
+ibf_key_from_hashcode (const struct GNUNET_HashCode *hash);
+
+
+/**
+ * Create a hashcode from a key, by replicating the key
+ * until the hascode is filled
+ *
+ * @param key the key
+ * @param dst hashcode to store the result in
+ */
+void
+ibf_hashcode_from_key (struct IBF_Key key, struct GNUNET_HashCode *dst);
+
+
+/**
+ * Create an invertible bloom filter.
+ *
+ * @param size number of IBF buckets
+ * @param hash_num number of buckets one element is hashed in, usually 3 or 4
+ * @return the newly created invertible bloom filter, NULL on error
+ */
+struct InvertibleBloomFilter *
+ibf_create (uint32_t size, uint8_t hash_num);
+
+
+/**
+ * Insert a key into an IBF.
+ *
+ * @param ibf the IBF
+ * @param key the element's hash code
+ */
+void
+ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key key);
+
+
+/**
+ * Remove a key from an IBF.
+ *
+ * @param ibf the IBF
+ * @param key the element's hash code
+ */
+void
+ibf_remove (struct InvertibleBloomFilter *ibf, struct IBF_Key key);
+
+
+/**
+ * Subtract ibf2 from ibf1, storing the result in ibf1.
+ * The two IBF's must have the same parameters size and hash_num.
+ *
+ * @param ibf1 IBF that is subtracted from
+ * @param ibf2 IBF that will be subtracted from ibf1
+ */
+void
+ibf_subtract (struct InvertibleBloomFilter *ibf1,
+              const struct InvertibleBloomFilter *ibf2);
+
+
+/**
+ * Decode and remove an element from the IBF, if possible.
+ *
+ * @param ibf the invertible bloom filter to decode
+ * @param ret_side sign of the cell's count where the decoded element came from.
+ *                 A negative sign indicates that the element was recovered
+ *                 resides in an IBF that was previously subtracted from.
+ * @param ret_id receives the hash code of the decoded element, if successful
+ * @return #GNUNET_YES if decoding an element was successful,
+ *         #GNUNET_NO if the IBF is empty,
+ *         #GNUNET_SYSERR if the decoding has failed
+ */
+int
+ibf_decode (struct InvertibleBloomFilter *ibf,
+            int *ret_side,
+            struct IBF_Key *ret_id);
+
+
+/**
+ * Create a copy of an IBF, the copy has to be destroyed properly.
+ *
+ * @param ibf the IBF to copy
+ */
+struct InvertibleBloomFilter *
+ibf_dup (const struct InvertibleBloomFilter *ibf);
+
+
+/**
+ * Destroy all resources associated with the invertible bloom filter.
+ * No more ibf_*-functions may be called on ibf after calling destroy.
+ *
+ * @param ibf the intertible bloom filter to destroy
+ */
+void
+ibf_destroy (struct InvertibleBloomFilter *ibf);
+
+uint8_t
+ibf_get_max_counter (struct InvertibleBloomFilter *ibf);
+
+
+/**
+ *  Packs the counter to transmit only the smallest possible amount of bytes and
+ *  preventing overflow of the counter
+ * @param ibf the ibf to write
+ * @param start with which bucket to start
+ * @param count how many buckets to write
+ * @param buf buffer to write the data to
+ * @param max bit length of a counter for unpacking
+ */
+
+void
+pack_counter (const struct InvertibleBloomFilter *ibf,
+              uint32_t start,
+              uint64_t count,
+              uint8_t *buf,
+              uint8_t counter_max_length);
+
+/**
+ *  Unpacks the counter to transmit only the smallest possible amount of bytes and
+ *  preventing overflow of the counter
+ * @param ibf the ibf to write
+ * @param start with which bucket to start
+ * @param count how many buckets to write
+ * @param buf buffer to write the data to
+ * @param max bit length of a counter for unpacking
+ */
+
+void
+unpack_counter (const struct InvertibleBloomFilter *ibf,
+                uint32_t start,
+                uint64_t count,
+                uint8_t *buf,
+                uint8_t counter_max_length);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+#endif