diff --git a/CMakeLists.txt b/CMakeLists.txt
index ffbe44b..ca80a0c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,6 +51,8 @@ add_library(solanaceae_sha1_ngcft1
 	./solanaceae/ngc_ft1_sha1/hash_utils.hpp
 	./solanaceae/ngc_ft1_sha1/hash_utils.cpp
 
+	./solanaceae/ngc_ft1_sha1/util.hpp
+
 	./solanaceae/ngc_ft1_sha1/ft1_sha1_info.hpp
 	./solanaceae/ngc_ft1_sha1/ft1_sha1_info.cpp
 
diff --git a/solanaceae/ngc_ft1_sha1/receiving_transfers.cpp b/solanaceae/ngc_ft1_sha1/receiving_transfers.cpp
index 6ab4831..f7b6f61 100644
--- a/solanaceae/ngc_ft1_sha1/receiving_transfers.cpp
+++ b/solanaceae/ngc_ft1_sha1/receiving_transfers.cpp
@@ -27,22 +27,22 @@ void ReceivingTransfers::tick(float delta) {
 	}
 }
 
-ReceivingTransfers::Entry& ReceivingTransfers::emplaceInfo(uint64_t combined_id, uint8_t transfer_id, const Entry::Info& info) {
-	auto& ent = _data[combined_id][transfer_id];
+ReceivingTransfers::Entry& ReceivingTransfers::emplaceInfo(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id, const Entry::Info& info) {
+	auto& ent = _data[combine_ids(group_number, peer_number)][transfer_id];
 	ent.v = info;
 	return ent;
 }
 
-ReceivingTransfers::Entry& ReceivingTransfers::emplaceChunk(uint64_t combined_id, uint8_t transfer_id, const Entry::Chunk& chunk) {
+ReceivingTransfers::Entry& ReceivingTransfers::emplaceChunk(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id, const Entry::Chunk& chunk) {
 	assert(!chunk.chunk_indices.empty());
-	assert(!containsPeerChunk(combined_id, chunk.content, chunk.chunk_indices.front()));
-	auto& ent = _data[combined_id][transfer_id];
+	assert(!containsPeerChunk(group_number, peer_number, chunk.content, chunk.chunk_indices.front()));
+	auto& ent = _data[combine_ids(group_number, peer_number)][transfer_id];
 	ent.v = chunk;
 	return ent;
 }
 
-bool ReceivingTransfers::containsPeerTransfer(uint64_t combined_id, uint8_t transfer_id) const {
-	auto it = _data.find(combined_id);
+bool ReceivingTransfers::containsPeerTransfer(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id) const {
+	auto it = _data.find(combine_ids(group_number, peer_number));
 	if (it == _data.end()) {
 		return false;
 	}
@@ -73,8 +73,8 @@ bool ReceivingTransfers::containsChunk(ObjectHandle o, size_t chunk_idx) const {
 	return false;
 }
 
-bool ReceivingTransfers::containsPeerChunk(uint64_t combined_id, ObjectHandle o, size_t chunk_idx) const {
-	auto it = _data.find(combined_id);
+bool ReceivingTransfers::containsPeerChunk(uint32_t group_number, uint32_t peer_number, ObjectHandle o, size_t chunk_idx) const {
+	auto it = _data.find(combine_ids(group_number, peer_number));
 	if (it == _data.end()) {
 		return false;
 	}
@@ -99,12 +99,12 @@ bool ReceivingTransfers::containsPeerChunk(uint64_t combined_id, ObjectHandle o,
 	return false;
 }
 
-void ReceivingTransfers::removePeer(uint64_t combined_id) {
-	_data.erase(combined_id);
+void ReceivingTransfers::removePeer(uint32_t group_number, uint32_t peer_number) {
+	_data.erase(combine_ids(group_number, peer_number));
 }
 
-void ReceivingTransfers::removePeerTransfer(uint64_t combined_id, uint8_t transfer_id) {
-	auto it = _data.find(combined_id);
+void ReceivingTransfers::removePeerTransfer(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id) {
+	auto it = _data.find(combine_ids(group_number, peer_number));
 	if (it == _data.end()) {
 		return;
 	}
@@ -120,8 +120,8 @@ size_t ReceivingTransfers::size(void) const {
 	return count;
 }
 
-size_t ReceivingTransfers::sizePeer(uint64_t combined_id) const {
-	auto it = _data.find(combined_id);
+size_t ReceivingTransfers::sizePeer(uint32_t group_number, uint32_t peer_number) const {
+	auto it = _data.find(combine_ids(group_number, peer_number));
 	if (it == _data.end()) {
 		return 0;
 	}
diff --git a/solanaceae/ngc_ft1_sha1/receiving_transfers.hpp b/solanaceae/ngc_ft1_sha1/receiving_transfers.hpp
index bd7504f..dfc8772 100644
--- a/solanaceae/ngc_ft1_sha1/receiving_transfers.hpp
+++ b/solanaceae/ngc_ft1_sha1/receiving_transfers.hpp
@@ -4,6 +4,8 @@
 
 #include <entt/container/dense_map.hpp>
 
+#include "./util.hpp"
+
 #include <cstdint>
 #include <variant>
 #include <vector>
@@ -44,21 +46,21 @@ struct ReceivingTransfers {
 
 	void tick(float delta);
 
-	Entry& emplaceInfo(uint64_t combined_id, uint8_t transfer_id, const Entry::Info& info);
-	Entry& emplaceChunk(uint64_t combined_id, uint8_t transfer_id, const Entry::Chunk& chunk);
+	Entry& emplaceInfo(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id, const Entry::Info& info);
+	Entry& emplaceChunk(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id, const Entry::Chunk& chunk);
 
-	bool containsPeer(uint64_t combined_id) const { return _data.count(combined_id); }
-	bool containsPeerTransfer(uint64_t combined_id, uint8_t transfer_id) const;
+	bool containsPeer(uint32_t group_number, uint32_t peer_number) const { return _data.count(combine_ids(group_number, peer_number)); }
+	bool containsPeerTransfer(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id) const;
 	bool containsChunk(ObjectHandle o, size_t chunk_idx) const;
-	bool containsPeerChunk(uint64_t combined_id, ObjectHandle o, size_t chunk_idx) const;
+	bool containsPeerChunk(uint32_t group_number, uint32_t peer_number, ObjectHandle o, size_t chunk_idx) const;
 
-	auto& getPeer(uint64_t combined_id) { return _data.at(combined_id); }
-	auto& getTransfer(uint64_t combined_id, uint8_t transfer_id) { return getPeer(combined_id).at(transfer_id); }
+	auto& getPeer(uint32_t group_number, uint32_t peer_number) { return _data.at(combine_ids(group_number, peer_number)); }
+	auto& getTransfer(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id) { return getPeer(group_number, peer_number).at(transfer_id); }
 
-	void removePeer(uint64_t combined_id);
-	void removePeerTransfer(uint64_t combined_id, uint8_t transfer_id);
+	void removePeer(uint32_t group_number, uint32_t peer_number);
+	void removePeerTransfer(uint32_t group_number, uint32_t peer_number, uint8_t transfer_id);
 
 	size_t size(void) const;
-	size_t sizePeer(uint64_t combined_id) const;
+	size_t sizePeer(uint32_t group_number, uint32_t peer_number) const;
 };
 
diff --git a/solanaceae/ngc_ft1_sha1/sha1_ngcft1.cpp b/solanaceae/ngc_ft1_sha1/sha1_ngcft1.cpp
index f8b7dd6..c7fbe3a 100644
--- a/solanaceae/ngc_ft1_sha1/sha1_ngcft1.cpp
+++ b/solanaceae/ngc_ft1_sha1/sha1_ngcft1.cpp
@@ -7,6 +7,8 @@
 #include <solanaceae/message3/components.hpp>
 #include <solanaceae/tox_messages/components.hpp>
 
+#include "./util.hpp"
+
 #include "./ft1_sha1_info.hpp"
 #include "./hash_utils.hpp"
 
@@ -53,8 +55,8 @@ void SHA1_NGCFT1::queueUpRequestChunk(uint32_t group_number, uint32_t peer_numbe
 	}
 
 	// check for running transfer
-	if (_sending_transfers.count(combineIds(group_number, peer_number))) {
-		for (const auto& [_, transfer] : _sending_transfers.at(combineIds(group_number, peer_number))) {
+	if (_sending_transfers.count(combine_ids(group_number, peer_number))) {
+		for (const auto& [_, transfer] : _sending_transfers.at(combine_ids(group_number, peer_number))) {
 			if (std::holds_alternative<SendingTransfer::Info>(transfer.v)) {
 				// ignore info
 				continue;
@@ -82,10 +84,6 @@ void SHA1_NGCFT1::queueUpRequestChunk(uint32_t group_number, uint32_t peer_numbe
 	_queue_requested_chunk.push_back(std::make_tuple(group_number, peer_number, content, hash, 0.f));
 }
 
-uint64_t SHA1_NGCFT1::combineIds(const uint32_t group_number, const uint32_t peer_number) {
-	return (uint64_t(group_number) << 32) | peer_number;
-}
-
 void SHA1_NGCFT1::updateMessages(ObjectHandle ce) {
 	assert(ce.all_of<Components::Messages>());
 
@@ -322,8 +320,8 @@ void SHA1_NGCFT1::iterate(float delta) {
 
 				// check if already sending
 				bool already_sending_to_this_peer = false;
-				if (_sending_transfers.count(combineIds(group_number, peer_number))) {
-					for (const auto& [_2, t] : _sending_transfers.at(combineIds(group_number, peer_number))) {
+				if (_sending_transfers.count(combine_ids(group_number, peer_number))) {
+					for (const auto& [_2, t] : _sending_transfers.at(combine_ids(group_number, peer_number))) {
 						if (std::holds_alternative<SendingTransfer::Chunk>(t.v)) {
 							const auto& v = std::get<SendingTransfer::Chunk>(t.v);
 							if (v.content == ce && v.chunk_index == chunk_idx_vec.front()) {
@@ -347,7 +345,7 @@ void SHA1_NGCFT1::iterate(float delta) {
 						&transfer_id
 					)) {
 						_sending_transfers
-							[combineIds(group_number, peer_number)]
+							[combine_ids(group_number, peer_number)]
 							[transfer_id] // TODO: also save index?
 								.v = SendingTransfer::Chunk{ce, chunk_idx_vec.front()};
 					}
@@ -631,7 +629,7 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_request& e) {
 		);
 
 		_sending_transfers
-			[combineIds(e.group_number, e.peer_number)]
+			[combine_ids(e.group_number, e.peer_number)]
 			[transfer_id]
 				.v = SendingTransfer::Info{content.get<Components::FT1InfoSHA1Data>().data};
 	} else if (e.file_kind == NGCFT1_file_kind::HASH_SHA1_CHUNK) {
@@ -699,7 +697,7 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_init& e) {
 		}
 
 		_receiving_transfers.emplaceInfo(
-			combineIds(e.group_number, e.peer_number),
+			e.group_number, e.peer_number,
 			e.transfer_id,
 			{ce, std::vector<uint8_t>(e.file_size)}
 		);
@@ -743,7 +741,7 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_init& e) {
 		assert(e.file_size == info.chunkSize(idx_vec.front()));
 
 		_receiving_transfers.emplaceChunk(
-			combineIds(e.group_number, e.peer_number),
+			e.group_number, e.peer_number,
 			e.transfer_id,
 			ReceivingTransfers::Entry::Chunk{ce, idx_vec}
 		);
@@ -759,11 +757,11 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_init& e) {
 }
 
 bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_data& e) {
-	if (!_receiving_transfers.containsPeerTransfer(combineIds(e.group_number, e.peer_number), e.transfer_id)) {
+	if (!_receiving_transfers.containsPeerTransfer(e.group_number, e.peer_number, e.transfer_id)) {
 		return false;
 	}
 
-	auto& transfer = _receiving_transfers.getTransfer(combineIds(e.group_number, e.peer_number), e.transfer_id);
+	auto& transfer = _receiving_transfers.getTransfer(e.group_number, e.peer_number, e.transfer_id);
 
 	transfer.time_since_activity = 0.f;
 	if (transfer.isInfo()) {
@@ -794,11 +792,11 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_data& e) {
 }
 
 bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_send_data& e) {
-	if (!_sending_transfers.count(combineIds(e.group_number, e.peer_number))) {
+	if (!_sending_transfers.count(combine_ids(e.group_number, e.peer_number))) {
 		return false;
 	}
 
-	auto& peer = _sending_transfers.at(combineIds(e.group_number, e.peer_number));
+	auto& peer = _sending_transfers.at(combine_ids(e.group_number, e.peer_number));
 
 	if (!peer.count(e.transfer_id)) {
 		return false;
@@ -846,11 +844,11 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_send_data& e) {
 }
 
 bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_done& e) {
-	if (!_receiving_transfers.containsPeerTransfer(combineIds(e.group_number, e.peer_number), e.transfer_id)) {
+	if (!_receiving_transfers.containsPeerTransfer(e.group_number, e.peer_number, e.transfer_id)) {
 		return false;
 	}
 
-	auto& transfer = _receiving_transfers.getTransfer(combineIds(e.group_number, e.peer_number), e.transfer_id);
+	auto& transfer = _receiving_transfers.getTransfer(e.group_number, e.peer_number, e.transfer_id);
 
 	if (transfer.isInfo()) {
 		auto& info = transfer.getInfo();
@@ -858,7 +856,7 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_done& e) {
 
 		if (o.any_of<Components::FT1InfoSHA1, Components::FT1InfoSHA1Data>()) {
 			// we already have the info, discard
-			_receiving_transfers.removePeerTransfer(combineIds(e.group_number, e.peer_number), e.transfer_id);
+			_receiving_transfers.removePeerTransfer(e.group_number, e.peer_number, e.transfer_id);
 			return true;
 		}
 
@@ -869,7 +867,7 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_done& e) {
 		if (o.get<Components::FT1InfoSHA1Hash>().hash != hash) {
 			std::cerr << "SHA1_NGCFT1 error: got info data mismatching its hash\n";
 			// TODO: requeue info request; eg manipulate o.get<Components::ReRequestInfoTimer>();
-			_receiving_transfers.removePeerTransfer(combineIds(e.group_number, e.peer_number), e.transfer_id);
+			_receiving_transfers.removePeerTransfer(e.group_number, e.peer_number, e.transfer_id);
 			return true;
 		}
 
@@ -997,17 +995,17 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_recv_done& e) {
 		updateMessages(o); // mostly for received bytes
 	}
 
-	_receiving_transfers.removePeerTransfer(combineIds(e.group_number, e.peer_number), e.transfer_id);
+	_receiving_transfers.removePeerTransfer(e.group_number, e.peer_number, e.transfer_id);
 
 	return true;
 }
 
 bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_send_done& e) {
-	if (!_sending_transfers.count(combineIds(e.group_number, e.peer_number))) {
+	if (!_sending_transfers.count(combine_ids(e.group_number, e.peer_number))) {
 		return false;
 	}
 
-	auto& peer_transfers = _sending_transfers.at(combineIds(e.group_number, e.peer_number));
+	auto& peer_transfers = _sending_transfers.at(combine_ids(e.group_number, e.peer_number));
 	if (!peer_transfers.count(e.transfer_id)) {
 		return false;
 	}
diff --git a/solanaceae/ngc_ft1_sha1/sha1_ngcft1.hpp b/solanaceae/ngc_ft1_sha1/sha1_ngcft1.hpp
index 217cee6..22bb203 100644
--- a/solanaceae/ngc_ft1_sha1/sha1_ngcft1.hpp
+++ b/solanaceae/ngc_ft1_sha1/sha1_ngcft1.hpp
@@ -80,8 +80,6 @@ class SHA1_NGCFT1 : public ToxEventI, public RegistryMessageModelEventI, public
 	using InfoBuilderEntry = std::function<void(void)>;
 	std::list<InfoBuilderEntry> _info_builder_queue;
 
-	static uint64_t combineIds(const uint32_t group_number, const uint32_t peer_number);
-
 	void updateMessages(ObjectHandle ce);
 
 	std::optional<std::pair<uint32_t, uint32_t>> selectPeerForRequest(ObjectHandle ce);
diff --git a/solanaceae/ngc_ft1_sha1/util.hpp b/solanaceae/ngc_ft1_sha1/util.hpp
new file mode 100644
index 0000000..9405b14
--- /dev/null
+++ b/solanaceae/ngc_ft1_sha1/util.hpp
@@ -0,0 +1,13 @@
+#pragma once
+
+#include <cstdint>
+
+inline static uint64_t combine_ids(const uint32_t group_number, const uint32_t peer_number) {
+	return (uint64_t(group_number) << 32) | peer_number;
+}
+
+inline static void decompose_ids(const uint64_t combined_id, uint32_t& group_number, uint32_t& peer_number) {
+	group_number = combined_id >> 32;
+	peer_number = combined_id & 0xffffffff;
+}
+