diff --git a/chihaya.go b/chihaya.go
index 8a7386b..9470485 100644
--- a/chihaya.go
+++ b/chihaya.go
@@ -12,10 +12,62 @@ import (
 )
 
 // PeerID represents a peer ID.
-type PeerID string
+type PeerID [20]byte
 
-// InfoHash represents an infohash in hexadecimal notation.
-type InfoHash string
+// PeerIDFromBytes creates a PeerID from a byte slice.
+//
+// It panics if b is not 20 bytes long.
+func PeerIDFromBytes(b []byte) PeerID {
+	if len(b) != 20 {
+		panic("peer ID must be 20 bytes")
+	}
+
+	var buf [20]byte
+	copy(buf[:], b)
+	return PeerID(buf)
+}
+
+// PeerIDFromString creates a PeerID from a string.
+//
+// It panics if s is not 20 bytes long.
+func PeerIDFromString(s string) PeerID {
+	if len(s) != 20 {
+		panic("peer ID must be 20 bytes")
+	}
+
+	var buf [20]byte
+	copy(buf[:], s)
+	return PeerID(buf)
+}
+
+// InfoHash represents an infohash.
+type InfoHash [20]byte
+
+// InfoHashFromBytes creates an InfoHash from a byte slice.
+//
+// It panics if b is not 20 bytes long.
+func InfoHashFromBytes(b []byte) InfoHash {
+	if len(b) != 20 {
+		panic("infohash must be 20 bytes")
+	}
+
+	var buf [20]byte
+	copy(buf[:], b)
+	return InfoHash(buf)
+}
+
+// InfoHashFromString creates an InfoHash from a string.
+//
+// It panics if s is not 20 bytes long.
+func InfoHashFromString(s string) InfoHash {
+	if len(s) != 20 {
+		panic("infohash must be 20 bytes")
+	}
+
+	var buf [20]byte
+	copy(buf[:], s)
+	return InfoHash(buf)
+}
 
 // AnnounceRequest represents the parsed parameters from an announce request.
 type AnnounceRequest struct {
diff --git a/chihaya_test.go b/chihaya_test.go
index 8b2d5b9..6fd513e 100644
--- a/chihaya_test.go
+++ b/chihaya_test.go
@@ -30,7 +30,7 @@ func TestPeerEquality(t *testing.T) {
 	var builtPeers []Peer
 	for _, peer := range peers {
 		builtPeers = append(builtPeers, Peer{
-			ID:   PeerID(peer.peerID),
+			ID:   PeerIDFromString(peer.peerID),
 			IP:   net.ParseIP(peer.ip),
 			Port: peer.port,
 		})
diff --git a/middleware/deniability/deniability_test.go b/middleware/deniability/deniability_test.go
index dbef933..4492898 100644
--- a/middleware/deniability/deniability_test.go
+++ b/middleware/deniability/deniability_test.go
@@ -42,7 +42,7 @@ func TestReplacePeer(t *testing.T) {
 		cfg: &cfg,
 	}
 	peer := chihaya.Peer{
-		ID:   chihaya.PeerID("abcdefghijklmnoprstu"),
+		ID:   chihaya.PeerID([20]byte{}),
 		Port: 2000,
 		IP:   net.ParseIP("10.150.255.23"),
 	}
@@ -77,7 +77,7 @@ func TestInsertPeer(t *testing.T) {
 		cfg: &cfg,
 	}
 	peer := chihaya.Peer{
-		ID:   chihaya.PeerID("abcdefghijklmnoprstu"),
+		ID:   chihaya.PeerID([20]byte{}),
 		Port: 2000,
 		IP:   net.ParseIP("10.150.255.23"),
 	}
diff --git a/pkg/random/peer.go b/pkg/random/peer.go
index c950221..c58a11f 100644
--- a/pkg/random/peer.go
+++ b/pkg/random/peer.go
@@ -67,7 +67,7 @@ func Peer(r *rand.Rand, prefix string, v6 bool, minPort, maxPort int) chihaya.Pe
 	prefix = prefix + AlphaNumericString(r, 20-len(prefix))
 
 	return chihaya.Peer{
-		ID:   chihaya.PeerID(prefix),
+		ID:   chihaya.PeerIDFromString(prefix),
 		Port: port,
 		IP:   ip,
 	}
diff --git a/pkg/random/peer_test.go b/pkg/random/peer_test.go
index f3c883c..636f42d 100644
--- a/pkg/random/peer_test.go
+++ b/pkg/random/peer_test.go
@@ -34,10 +34,10 @@ func TestPeer(t *testing.T) {
 	}
 
 	p := Peer(r, "abcdefghijklmnopqrst", false, 2000, 2000)
-	assert.Equal(t, "abcdefghijklmnopqrst", string(p.ID))
+	assert.Equal(t, "abcdefghijklmnopqrst", string(p.ID[:]))
 	assert.Equal(t, uint16(2000), p.Port)
 
 	p = Peer(r, "abcdefghijklmnopqrstUVWXYZ", true, -10, -5)
-	assert.Equal(t, "abcdefghijklmnopqrst", string(p.ID))
+	assert.Equal(t, "abcdefghijklmnopqrst", string(p.ID[:]))
 	assert.True(t, p.Port >= uint16(1) && p.Port <= uint16(65535))
 }
diff --git a/server/http/query/query.go b/server/http/query/query.go
index 5f51555..e8fe6e8 100644
--- a/server/http/query/query.go
+++ b/server/http/query/query.go
@@ -20,6 +20,10 @@ import (
 // it.
 var ErrKeyNotFound = errors.New("query: value for the provided key does not exist")
 
+// ErrInvalidInfohash is returned when parsing a query encounters an infohash
+// with invalid length.
+var ErrInvalidInfohash = errors.New("query: invalid infohash")
+
 // Query represents a parsed URL.Query.
 type Query struct {
 	query      string
@@ -71,7 +75,10 @@ func New(query string) (*Query, error) {
 			}
 
 			if keyStr == "info_hash" {
-				q.infoHashes = append(q.infoHashes, chihaya.InfoHash(valStr))
+				if len(valStr) != 20 {
+					return nil, ErrInvalidInfohash
+				}
+				q.infoHashes = append(q.infoHashes, chihaya.InfoHashFromString(valStr))
 			} else {
 				q.params[strings.ToLower(keyStr)] = valStr
 			}
diff --git a/server/http/request.go b/server/http/request.go
index 354c3b7..5d17aad 100644
--- a/server/http/request.go
+++ b/server/http/request.go
@@ -49,7 +49,10 @@ func announceRequest(r *http.Request, cfg *httpConfig) (*chihaya.AnnounceRequest
 	if err != nil {
 		return nil, tracker.ClientError("failed to parse parameter: peer_id")
 	}
-	request.PeerID = chihaya.PeerID(peerID)
+	if len(peerID) != 20 {
+		return nil, tracker.ClientError("failed to provide valid peer_id")
+	}
+	request.PeerID = chihaya.PeerIDFromString(peerID)
 
 	request.Left, err = q.Uint64("left")
 	if err != nil {
diff --git a/server/http/writer.go b/server/http/writer.go
index 5f9eda0..5de6c3d 100644
--- a/server/http/writer.go
+++ b/server/http/writer.go
@@ -71,7 +71,7 @@ func writeAnnounceResponse(w http.ResponseWriter, resp *chihaya.AnnounceResponse
 func writeScrapeResponse(w http.ResponseWriter, resp *chihaya.ScrapeResponse) error {
 	filesDict := bencode.NewDict()
 	for infohash, scrape := range resp.Files {
-		filesDict[string(infohash)] = bencode.Dict{
+		filesDict[string(infohash[:])] = bencode.Dict{
 			"complete":   scrape.Complete,
 			"incomplete": scrape.Incomplete,
 		}
@@ -91,7 +91,7 @@ func compact(peer chihaya.Peer) (buf []byte) {
 
 func dict(peer chihaya.Peer) bencode.Dict {
 	return bencode.Dict{
-		"peer id": string(peer.ID),
+		"peer id": string(peer.ID[:]),
 		"ip":      peer.IP.String(),
 		"port":    peer.Port,
 	}
diff --git a/server/store/memory/peer_store.go b/server/store/memory/peer_store.go
index 6638940..7ab1cd9 100644
--- a/server/store/memory/peer_store.go
+++ b/server/store/memory/peer_store.go
@@ -78,20 +78,20 @@ var _ store.PeerStore = &peerStore{}
 
 func (s *peerStore) shardIndex(infoHash chihaya.InfoHash) uint32 {
 	idx := fnv.New32()
-	idx.Write([]byte(infoHash))
+	idx.Write(infoHash[:])
 	return idx.Sum32() % uint32(len(s.shards))
 }
 
 func peerKey(p chihaya.Peer) string {
-	return string(p.IP) + string(p.ID)
+	return string(p.IP) + string(p.ID[:])
 }
 
 func seedersKey(infoHash chihaya.InfoHash) string {
-	return string(infoHash) + "-s"
+	return string(infoHash[:]) + "-s"
 }
 
 func leechersKey(infoHash chihaya.InfoHash) string {
-	return string(infoHash) + "-l"
+	return string(infoHash[:]) + "-l"
 }
 
 func (s *peerStore) PutSeeder(infoHash chihaya.InfoHash, p chihaya.Peer) error {
diff --git a/server/store/memory/peer_store_test.go b/server/store/memory/peer_store_test.go
index 157e00e..8eb6a0c 100644
--- a/server/store/memory/peer_store_test.go
+++ b/server/store/memory/peer_store_test.go
@@ -25,7 +25,7 @@ func peerInSlice(peer chihaya.Peer, peers []chihaya.Peer) bool {
 
 func TestPeerStoreAPI(t *testing.T) {
 	var (
-		hash = chihaya.InfoHash("11111111111111111111")
+		hash = chihaya.InfoHash([20]byte{})
 
 		peers = []struct {
 			seeder bool
@@ -62,7 +62,7 @@ func TestPeerStoreAPI(t *testing.T) {
 	for _, p := range peers {
 		// Construct chihaya.Peer from test data.
 		peer := chihaya.Peer{
-			ID:   chihaya.PeerID(p.peerID),
+			ID:   chihaya.PeerIDFromString(p.peerID),
 			IP:   net.ParseIP(p.ip),
 			Port: p.port,
 		}
@@ -95,7 +95,7 @@ func TestPeerStoreAPI(t *testing.T) {
 	for _, p := range peers {
 		// Construct chihaya.Peer from test data.
 		peer := chihaya.Peer{
-			ID:   chihaya.PeerID(p.peerID),
+			ID:   chihaya.PeerIDFromString(p.peerID),
 			IP:   net.ParseIP(p.ip),
 			Port: p.port,
 		}
@@ -121,7 +121,7 @@ func TestPeerStoreAPI(t *testing.T) {
 	for _, p := range peers {
 		// Construct chihaya.Peer from test data.
 		peer := chihaya.Peer{
-			ID:   chihaya.PeerID(p.peerID),
+			ID:   chihaya.PeerIDFromString(p.peerID),
 			IP:   net.ParseIP(p.ip),
 			Port: p.port,
 		}
@@ -136,7 +136,7 @@ func TestPeerStoreAPI(t *testing.T) {
 	assert.Equal(t, 6, s.NumSeeders(hash))
 	assert.Equal(t, 4, s.NumLeechers(hash))
 	peer := chihaya.Peer{
-		ID:   chihaya.PeerID(peers[0].peerID),
+		ID:   chihaya.PeerIDFromString(peers[0].peerID),
 		IP:   net.ParseIP(peers[0].ip),
 		Port: peers[0].port,
 	}
diff --git a/server/store/middleware/client/blacklist.go b/server/store/middleware/client/blacklist.go
index ed675f9..e994d2f 100644
--- a/server/store/middleware/client/blacklist.go
+++ b/server/store/middleware/client/blacklist.go
@@ -23,7 +23,7 @@ var ErrBlacklistedClient = tracker.ClientError("client blacklisted")
 // announce that are not stored in the StringStore.
 func blacklistAnnounceClient(next tracker.AnnounceHandler) tracker.AnnounceHandler {
 	return func(cfg *chihaya.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) error {
-		blacklisted, err := store.MustGetStore().HasString(PrefixClient + clientid.New(string(req.PeerID)))
+		blacklisted, err := store.MustGetStore().HasString(PrefixClient + clientid.New(string(req.PeerID[:])))
 		if err != nil {
 			return err
 		} else if blacklisted {
diff --git a/server/store/middleware/client/whitelist.go b/server/store/middleware/client/whitelist.go
index 980f6cd..275b56e 100644
--- a/server/store/middleware/client/whitelist.go
+++ b/server/store/middleware/client/whitelist.go
@@ -26,7 +26,7 @@ var ErrNotWhitelistedClient = tracker.ClientError("client not whitelisted")
 // announce that are stored in the StringStore.
 func whitelistAnnounceClient(next tracker.AnnounceHandler) tracker.AnnounceHandler {
 	return func(cfg *chihaya.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) error {
-		whitelisted, err := store.MustGetStore().HasString(PrefixClient + clientid.New(string(req.PeerID)))
+		whitelisted, err := store.MustGetStore().HasString(PrefixClient + clientid.New(string(req.PeerID[:])))
 		if err != nil {
 			return err
 		} else if !whitelisted {
diff --git a/server/store/middleware/infohash/blacklist.go b/server/store/middleware/infohash/blacklist.go
index 3595748..9a24320 100644
--- a/server/store/middleware/infohash/blacklist.go
+++ b/server/store/middleware/infohash/blacklist.go
@@ -28,7 +28,7 @@ var mustGetStore func() store.StringStore
 // for infohashes that are not stored in a StringStore.
 func blacklistAnnounceInfohash(next tracker.AnnounceHandler) tracker.AnnounceHandler {
 	return func(cfg *chihaya.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) (err error) {
-		blacklisted, err := mustGetStore().HasString(PrefixInfohash + string(req.InfoHash))
+		blacklisted, err := mustGetStore().HasString(PrefixInfohash + string(req.InfoHash[:]))
 		if err != nil {
 			return err
 		} else if blacklisted {
@@ -72,7 +72,7 @@ func blacklistFilterScrape(next tracker.ScrapeHandler) tracker.ScrapeHandler {
 		infohashes := req.InfoHashes
 
 		for i, ih := range infohashes {
-			blacklisted, err = storage.HasString(PrefixInfohash + string(ih))
+			blacklisted, err = storage.HasString(PrefixInfohash + string(ih[:]))
 
 			if err != nil {
 				return err
@@ -92,7 +92,7 @@ func blacklistBlockScrape(next tracker.ScrapeHandler) tracker.ScrapeHandler {
 		storage := mustGetStore()
 
 		for _, ih := range req.InfoHashes {
-			blacklisted, err = storage.HasString(PrefixInfohash + string(ih))
+			blacklisted, err = storage.HasString(PrefixInfohash + string(ih[:]))
 
 			if err != nil {
 				return err
diff --git a/server/store/middleware/infohash/blacklist_test.go b/server/store/middleware/infohash/blacklist_test.go
index cc06906..804a336 100644
--- a/server/store/middleware/infohash/blacklist_test.go
+++ b/server/store/middleware/infohash/blacklist_test.go
@@ -40,12 +40,17 @@ var mock store.StringStore = &storeMock{
 	strings: make(map[string]struct{}),
 }
 
+var (
+	ih1 = chihaya.InfoHash([20]byte{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
+	ih2 = chihaya.InfoHash([20]byte{2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
+)
+
 func TestASetUp(t *testing.T) {
 	mustGetStore = func() store.StringStore {
 		return mock
 	}
 
-	mustGetStore().PutString(PrefixInfohash + "abc")
+	mustGetStore().PutString(PrefixInfohash + string(ih1[:]))
 }
 
 func TestBlacklistAnnounceMiddleware(t *testing.T) {
@@ -61,11 +66,11 @@ func TestBlacklistAnnounceMiddleware(t *testing.T) {
 	err := handler(nil, &req, &resp)
 	assert.Nil(t, err)
 
-	req.InfoHash = chihaya.InfoHash("abc")
+	req.InfoHash = chihaya.InfoHash(ih1)
 	err = handler(nil, &req, &resp)
 	assert.Equal(t, ErrBlockedInfohash, err)
 
-	req.InfoHash = chihaya.InfoHash("def")
+	req.InfoHash = chihaya.InfoHash(ih2)
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 }
@@ -90,11 +95,11 @@ func TestBlacklistScrapeMiddlewareBlock(t *testing.T) {
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("abc"), chihaya.InfoHash("def")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih1), chihaya.InfoHash(ih2)}
 	err = handler(nil, &req, &resp)
 	assert.Equal(t, ErrBlockedInfohash, err)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("def")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih2)}
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 }
@@ -119,12 +124,12 @@ func TestBlacklistScrapeMiddlewareFilter(t *testing.T) {
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("abc"), chihaya.InfoHash("def")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih1), chihaya.InfoHash(ih2)}
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
-	assert.Equal(t, []chihaya.InfoHash{chihaya.InfoHash("def")}, req.InfoHashes)
+	assert.Equal(t, []chihaya.InfoHash{chihaya.InfoHash(ih2)}, req.InfoHashes)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("def")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih2)}
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 }
diff --git a/server/store/middleware/infohash/whitelist.go b/server/store/middleware/infohash/whitelist.go
index 85dec0c..99caeda 100644
--- a/server/store/middleware/infohash/whitelist.go
+++ b/server/store/middleware/infohash/whitelist.go
@@ -21,7 +21,7 @@ const PrefixInfohash = "ih-"
 // for infohashes that are not stored in a StringStore
 func whitelistAnnounceInfohash(next tracker.AnnounceHandler) tracker.AnnounceHandler {
 	return func(cfg *chihaya.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) (err error) {
-		whitelisted, err := mustGetStore().HasString(PrefixInfohash + string(req.InfoHash))
+		whitelisted, err := mustGetStore().HasString(PrefixInfohash + string(req.InfoHash[:]))
 
 		if err != nil {
 			return err
@@ -65,7 +65,7 @@ func whitelistFilterScrape(next tracker.ScrapeHandler) tracker.ScrapeHandler {
 		infohashes := req.InfoHashes
 
 		for i, ih := range infohashes {
-			whitelisted, err = storage.HasString(PrefixInfohash + string(ih))
+			whitelisted, err = storage.HasString(PrefixInfohash + string(ih[:]))
 
 			if err != nil {
 				return err
@@ -85,7 +85,7 @@ func whitelistBlockScrape(next tracker.ScrapeHandler) tracker.ScrapeHandler {
 		storage := mustGetStore()
 
 		for _, ih := range req.InfoHashes {
-			whitelisted, err = storage.HasString(PrefixInfohash + string(ih))
+			whitelisted, err = storage.HasString(PrefixInfohash + string(ih[:]))
 
 			if err != nil {
 				return err
diff --git a/server/store/middleware/infohash/whitelist_test.go b/server/store/middleware/infohash/whitelist_test.go
index f958638..3a68386 100644
--- a/server/store/middleware/infohash/whitelist_test.go
+++ b/server/store/middleware/infohash/whitelist_test.go
@@ -26,11 +26,11 @@ func TestWhitelistAnnounceMiddleware(t *testing.T) {
 	err := handler(nil, &req, &resp)
 	assert.Equal(t, ErrBlockedInfohash, err)
 
-	req.InfoHash = chihaya.InfoHash("def")
+	req.InfoHash = chihaya.InfoHash(ih2)
 	err = handler(nil, &req, &resp)
 	assert.Equal(t, ErrBlockedInfohash, err)
 
-	req.InfoHash = chihaya.InfoHash("abc")
+	req.InfoHash = chihaya.InfoHash(ih1)
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 }
@@ -55,11 +55,11 @@ func TestWhitelistScrapeMiddlewareBlock(t *testing.T) {
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("abc"), chihaya.InfoHash("def")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih1), chihaya.InfoHash(ih2)}
 	err = handler(nil, &req, &resp)
 	assert.Equal(t, ErrBlockedInfohash, err)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("abc")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih1)}
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 }
@@ -84,13 +84,13 @@ func TestWhitelistScrapeMiddlewareFilter(t *testing.T) {
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("abc"), chihaya.InfoHash("def")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih1), chihaya.InfoHash(ih2)}
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
-	assert.Equal(t, []chihaya.InfoHash{chihaya.InfoHash("abc")}, req.InfoHashes)
+	assert.Equal(t, []chihaya.InfoHash{chihaya.InfoHash(ih1)}, req.InfoHashes)
 
-	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash("abc")}
+	req.InfoHashes = []chihaya.InfoHash{chihaya.InfoHash(ih1)}
 	err = handler(nil, &req, &resp)
 	assert.Nil(t, err)
-	assert.Equal(t, []chihaya.InfoHash{chihaya.InfoHash("abc")}, req.InfoHashes)
+	assert.Equal(t, []chihaya.InfoHash{chihaya.InfoHash(ih1)}, req.InfoHashes)
 }