diff --git a/internal/chunk/obfuscate/ids.go b/internal/chunk/obfuscate/ids.go
new file mode 100644
index 00000000..20382a1a
--- /dev/null
+++ b/internal/chunk/obfuscate/ids.go
@@ -0,0 +1,41 @@
+package obfuscate
+
+import (
+	"encoding/hex"
+	"strings"
+)
+
+const (
+	userPrefix = "UO"
+	chanPrefix = "CO"
+	filePrefix = "FO"
+	teamPrefix = "TO"
+)
+
+// ID obfuscates an ID.
+func (o obfuscator) ID(prefix string, id string) string {
+	if id == "" {
+		return ""
+	}
+	h := o.hasher()
+	if _, err := h.Write([]byte(o.salt + id)); err != nil {
+		panic(err)
+	}
+	return prefix + strings.ToUpper(hex.EncodeToString(h.Sum(nil)))[:len(id)-1]
+}
+
+func (o obfuscator) UserID(u string) string {
+	return o.ID(userPrefix, u)
+}
+
+func (o obfuscator) ChannelID(c string) string {
+	return o.ID(chanPrefix, c)
+}
+
+func (o obfuscator) FileID(f string) string {
+	return o.ID(filePrefix, f)
+}
+
+func (o obfuscator) TeamID(g string) string {
+	return o.ID(teamPrefix, g)
+}
diff --git a/internal/chunk/obfuscate/obfuscate.go b/internal/chunk/obfuscate/obfuscate.go
index 1e41121e..1bf7d27d 100644
--- a/internal/chunk/obfuscate/obfuscate.go
+++ b/internal/chunk/obfuscate/obfuscate.go
@@ -8,7 +8,6 @@ package obfuscate
 import (
 	"context"
 	"crypto/sha256"
-	"encoding/hex"
 	"encoding/json"
 	"hash"
 	"io"
@@ -80,7 +79,7 @@ type obfuscator struct {
 }
 
 func (o obfuscator) Chunk(c *chunk.Chunk) {
-	c.ChannelID = o.ID("C", c.ChannelID)
+	c.ChannelID = o.ChannelID(c.ChannelID)
 	switch c.Type {
 	case chunk.CMessages:
 		o.Messages(c.Messages...)
@@ -105,7 +104,7 @@ func (o obfuscator) Messages(m ...slack.Message) {
 	}
 }
 
-const filePrefix = "https://files.slack.com/"
+const fileURLPrefix = "https://files.slack.com/"
 
 func notNilFn(s string, fn func(string) string) string {
 	if s != "" {
@@ -119,14 +118,14 @@ func (o obfuscator) OneMessage(m *slack.Message) {
 		return
 	}
 	m.ClientMsgID = notNilFn(m.ClientMsgID, func(s string) string { return randomUUID() })
-	m.Team = o.ID("T", m.Team)
-	m.Channel = o.ID("C", m.Channel)
-	m.User = o.ID("U", m.User)
+	m.Team = o.TeamID(m.Team)
+	m.Channel = o.UserID(m.Channel)
+	m.User = o.UserID(m.User)
 	if m.Text != "" {
 		m.Text = randomString(len(m.Text))
 	}
 	if m.Edited != nil {
-		m.Edited.User = o.ID("U", m.Edited.User)
+		m.Edited.User = o.UserID(m.Edited.User)
 	}
 	if len(m.Blocks.BlockSet) > 0 {
 		m.Blocks.BlockSet = nil // too much hassle to obfuscate
@@ -138,7 +137,7 @@ func (o obfuscator) OneMessage(m *slack.Message) {
 		m.Attachments = nil // too much hassle to obfuscate
 	}
 	if m.ParentUserId != "" {
-		m.ParentUserId = o.ID("U", m.ParentUserId)
+		m.ParentUserId = o.UserID(m.ParentUserId)
 	}
 	for i := range m.Files {
 		o.OneFile(&m.Files[i])
@@ -157,8 +156,8 @@ func (o obfuscator) OneFile(f *slack.File) {
 	}
 	ifnotnil := func(s string) string {
 		if s != "" {
-			if strings.HasPrefix(s, filePrefix) {
-				s = filePrefix + randomString(len(s)-len(filePrefix))
+			if strings.HasPrefix(s, fileURLPrefix) {
+				s = fileURLPrefix + randomString(len(s)-len(fileURLPrefix))
 			} else {
 				s = randomString(len(s))
 			}
@@ -198,8 +197,8 @@ func (o obfuscator) OneFile(f *slack.File) {
 	f.OriginalW = 0
 	f.OriginalH = 0
 	f.InitialComment = slack.Comment{}
-	f.User = o.ID("U", f.User)
-	f.ID = o.ID("F", f.ID)
+	f.User = o.UserID(f.User)
+	f.ID = o.FileID(f.ID)
 }
 
 // randomString returns a random string of length n + random number [0,40).
@@ -241,23 +240,11 @@ func randomUUID() string {
 	return string(b)
 }
 
-// ID obfuscates an ID.
-func (o obfuscator) ID(prefix string, id string) string {
-	if id == "" {
-		return ""
-	}
-	h := o.hasher()
-	if _, err := h.Write([]byte(o.salt + id)); err != nil {
-		panic(err)
-	}
-	return prefix + strings.ToUpper(hex.EncodeToString(h.Sum(nil)))[:len(id)-1]
-}
-
 func (o obfuscator) Reactions(r []slack.ItemReaction) {
 	for i := range r {
 		r[i].Name = randomStringExact(len(r[i].Name))
 		for j := range r[i].Users {
-			r[i].Users[j] = o.ID("U", r[i].Users[j])
+			r[i].Users[j] = o.UserID(r[i].Users[j])
 		}
 	}
 }
@@ -266,13 +253,18 @@ func (o obfuscator) Channel(c *slack.Channel) {
 	if c == nil {
 		return
 	}
-	c.ID = o.ID("C", c.ID)
-	c.Creator = o.ID("U", c.Creator)
+	c.ID = o.ChannelID(c.ID)
+	c.Creator = o.UserID(c.Creator)
 	c.Name = o.ID("", c.Name)
 	c.NameNormalized = o.ID("", c.NameNormalized)
+
 	c.Purpose.Value = randomStringExact(len(c.Purpose.Value))
+	c.Purpose.Creator = o.UserID(c.Purpose.Creator)
+
 	c.Topic.Value = randomStringExact(len(c.Topic.Value))
+	c.Topic.Creator = o.UserID(c.Topic.Creator)
+
 	for i := range c.Members {
-		c.Members[i] = o.ID("U", c.Members[i])
+		c.Members[i] = o.UserID(c.Members[i])
 	}
 }
diff --git a/internal/chunk/obfuscate/obfuscate_test.go b/internal/chunk/obfuscate/obfuscate_test.go
index f3bbb893..2876377e 100644
--- a/internal/chunk/obfuscate/obfuscate_test.go
+++ b/internal/chunk/obfuscate/obfuscate_test.go
@@ -141,10 +141,10 @@ func Test_obfuscator_OneMessage(t *testing.T) {
 					ClientMsgID: "a29ab0f5-808b-bc8e-f22e-b4ac1a00fcd4",
 					Type:        "message",
 					Channel:     "",
-					User:        "U8EEA06E1",
+					User:        userPrefix + "8EEA06E1",
 					Text:        "9 LVwGabEN7FkWNmyD0HtOdvcYYvfHfF hVA6Nd1BtVOw52BH40tQ4xsZr1rbOE",
 					Timestamp:   "1645095505.023899",
-					Team:        "TEBC93378",
+					Team:        teamPrefix + "EBC93378",
 				},
 			},
 		},
@@ -199,7 +199,7 @@ func Test_obfuscator_OneFile(t *testing.T) {
 				f: fixtures.Load[*slack.File](fixtures.FileJPEG),
 			},
 			wantFile: &slack.File{
-				ID:                 "F8B5BAA15C4",
+				ID:                 filePrefix + "8B5BAA15C4",
 				Created:            1638784624,
 				Timestamp:          1638784624,
 				Name:               "N1CIe93m6sjyQtxxQ",
@@ -207,7 +207,7 @@ func Test_obfuscator_OneFile(t *testing.T) {
 				Mimetype:           "image/jpeg",
 				Filetype:           "jpg",
 				PrettyType:         "JPEG",
-				User:               "U8EEA06E1",
+				User:               userPrefix + "8EEA06E1",
 				Mode:               "hosted",
 				Size:               359002,
 				URLPrivate:         "https://files.slack.com/jXUJR9JT5pul5g8MDbK7E1ycTwBhzdJG9 LVwGabEN7FkWNmyD0HtOdvcYYvfHfF hVA6Nd1BtVOw52BH40tQ4xsZr1rbOEdndtLrooKH5L9GzLgWmmWfVTBKfSvym98qEQMYaWdLEKrJCEXzYB2bFiOLzhK",
@@ -246,10 +246,12 @@ var testChan = &slack.Channel{
 		IsArchived: false,
 		Creator:    "U024BE7LH",
 		Topic: slack.Topic{
-			Value: "Fun times",
+			Value:   "Fun times",
+			Creator: "U024BE7LV",
 		},
 		Purpose: slack.Purpose{
-			Value: "A place for non-work-related flimflam.",
+			Value:   "A place for non-work-related flimflam.",
+			Creator: "U024BE7LH",
 		},
 		Conversation: slack.Conversation{
 			ID:      "C0G9QF9GW",
@@ -287,15 +289,17 @@ func Test_obfuscator_Channel(t *testing.T) {
 				GroupConversation: slack.GroupConversation{
 					Name:       "55D55",
 					IsArchived: false,
-					Creator:    "UF209DFAC",
+					Creator:    userPrefix + "F209DFAC",
 					Topic: slack.Topic{
-						Value: "GabEN7FkW",
+						Value:   "GabEN7FkW",
+						Creator: userPrefix + "0077C5B4",
 					},
 					Purpose: slack.Purpose{
-						Value: "2jXUJR9JT5pul5g8MDbK7E1ycTwBhzdJG9 LVw",
+						Value:   "2jXUJR9JT5pul5g8MDbK7E1ycTwBhzdJG9 LVw",
+						Creator: userPrefix + "F209DFAC",
 					},
 					Conversation: slack.Conversation{
-						ID:      "C0250C11A",
+						ID:      chanPrefix + "0250C11A",
 						IsGroup: false,
 						Created: 1449252882,
 					},
diff --git a/internal/fixtures/assets/chunks.jsonl.gz b/internal/fixtures/assets/chunks.jsonl.gz
index 962a5ac3..8c83967a 100644
Binary files a/internal/fixtures/assets/chunks.jsonl.gz and b/internal/fixtures/assets/chunks.jsonl.gz differ
diff --git a/internal/fixtures/chunk.go b/internal/fixtures/chunk.go
index 96acac50..a177341f 100644
--- a/internal/fixtures/chunk.go
+++ b/internal/fixtures/chunk.go
@@ -14,7 +14,7 @@ import (
 //go:embed assets/chunks.jsonl.gz
 var chunksJsonlGz []byte
 
-const ChunkFileChannelID = "C73D19AAE17"
+const ChunkFileChannelID = "CO73D19AAE17"
 
 // chunksJSONL returns a reader for the b []byte, which assumed to be a
 // gzip-compressed bytes slice. It panics on error.