diff --git a/changes/ticket28913 b/changes/ticket28913
new file mode 100644
index 0000000000..e09847464d
--- /dev/null
+++ b/changes/ticket28913
@@ -0,0 +1,4 @@
+  o Code simplification and refactoring:
+    - Make the base32_decode() API return the number of bytes written,
+      for consistency with base64_decode().
+      Closes ticket 28913.
diff --git a/src/feature/control/control.c b/src/feature/control/control.c
index e95e58d919..f4bb0d38a8 100644
--- a/src/feature/control/control.c
+++ b/src/feature/control/control.c
@@ -4444,7 +4444,8 @@ handle_control_hsfetch(control_connection_t *conn, uint32_t len,
   } else if (strcmpstart(arg1, v2_str) == 0 &&
              rend_valid_descriptor_id(arg1 + v2_str_len) &&
              base32_decode(digest, sizeof(digest), arg1 + v2_str_len,
-                           REND_DESC_ID_V2_LEN_BASE32) == 0) {
+                           REND_DESC_ID_V2_LEN_BASE32) ==
+                REND_DESC_ID_V2_LEN_BASE32) {
     /* We have a well formed version 2 descriptor ID. Keep the decoded value
      * of the id. */
     desc_id = digest;
diff --git a/src/feature/hs/hs_client.c b/src/feature/hs/hs_client.c
index e1d0e8613a..075f1d5c41 100644
--- a/src/feature/hs/hs_client.c
+++ b/src/feature/hs/hs_client.c
@@ -1561,7 +1561,10 @@ parse_auth_file_content(const char *client_key_str)
   auth = tor_malloc_zero(sizeof(hs_client_service_authorization_t));
   if (base32_decode((char *) auth->enc_seckey.secret_key,
                     sizeof(auth->enc_seckey.secret_key),
-                    seckey_b32, strlen(seckey_b32)) < 0) {
+                    seckey_b32, strlen(seckey_b32)) !=
+      sizeof(auth->enc_seckey.secret_key)) {
+    log_warn(LD_REND, "Client authorization encoded base32 private key "
+                      "can't be decoded: %s", seckey_b32);
     goto err;
   }
   strncpy(auth->onion_address, onion_address, HS_SERVICE_ADDR_LEN_BASE32);
diff --git a/src/feature/hs/hs_common.c b/src/feature/hs/hs_common.c
index ebe49f09a5..14655c53a5 100644
--- a/src/feature/hs/hs_common.c
+++ b/src/feature/hs/hs_common.c
@@ -926,7 +926,8 @@ hs_parse_address(const char *address, ed25519_public_key_t *key_out,
   }
 
   /* Decode address so we can extract needed fields. */
-  if (base32_decode(decoded, sizeof(decoded), address, strlen(address)) < 0) {
+  if (base32_decode(decoded, sizeof(decoded), address, strlen(address))
+      != sizeof(decoded)) {
     log_warn(LD_REND, "Service address %s can't be decoded.",
              escaped_safe_str(address));
     goto invalid;
diff --git a/src/feature/hs/hs_service.c b/src/feature/hs/hs_service.c
index b94dd9a481..8d286f2bad 100644
--- a/src/feature/hs/hs_service.c
+++ b/src/feature/hs/hs_service.c
@@ -1179,7 +1179,8 @@ parse_authorized_client(const char *client_key_str)
   client = tor_malloc_zero(sizeof(hs_service_authorized_client_t));
   if (base32_decode((char *) client->client_pk.public_key,
                     sizeof(client->client_pk.public_key),
-                    pubkey_b32, strlen(pubkey_b32)) < 0) {
+                    pubkey_b32, strlen(pubkey_b32)) !=
+      sizeof(client->client_pk.public_key)) {
     log_warn(LD_REND, "Client authorization public key cannot be decoded: %s",
              pubkey_b32);
     goto err;
diff --git a/src/feature/rend/rendcache.c b/src/feature/rend/rendcache.c
index fadfb43883..abeb150685 100644
--- a/src/feature/rend/rendcache.c
+++ b/src/feature/rend/rendcache.c
@@ -593,10 +593,10 @@ rend_cache_lookup_v2_desc_as_dir(const char *desc_id, const char **desc)
   char desc_id_digest[DIGEST_LEN];
   tor_assert(rend_cache_v2_dir);
   if (base32_decode(desc_id_digest, DIGEST_LEN,
-                    desc_id, REND_DESC_ID_V2_LEN_BASE32) < 0) {
+                    desc_id, REND_DESC_ID_V2_LEN_BASE32) != DIGEST_LEN) {
     log_fn(LOG_PROTOCOL_WARN, LD_REND,
            "Rejecting v2 rendezvous descriptor request -- descriptor ID "
-           "contains illegal characters: %s",
+           "has wrong length or illegal characters: %s",
            safe_str(desc_id));
     return -1;
   }
@@ -854,7 +854,8 @@ rend_cache_store_v2_desc_as_client(const char *desc,
     *entry = NULL;
   }
   if (base32_decode(want_desc_id, sizeof(want_desc_id),
-                    desc_id_base32, strlen(desc_id_base32)) != 0) {
+                    desc_id_base32, strlen(desc_id_base32)) !=
+      sizeof(want_desc_id)) {
     log_warn(LD_BUG, "Couldn't decode base32 %s for descriptor id.",
              escaped_safe_str_client(desc_id_base32));
     goto err;
@@ -1005,4 +1006,3 @@ rend_cache_store_v2_desc_as_client(const char *desc,
   tor_free(intro_content);
   return retval;
 }
-
diff --git a/src/feature/rend/rendcommon.c b/src/feature/rend/rendcommon.c
index de48af795f..5cc054f454 100644
--- a/src/feature/rend/rendcommon.c
+++ b/src/feature/rend/rendcommon.c
@@ -171,9 +171,10 @@ rend_compute_v2_desc_id(char *desc_id_out, const char *service_id,
   }
   /* Convert service ID to binary. */
   if (base32_decode(service_id_binary, REND_SERVICE_ID_LEN,
-                    service_id, REND_SERVICE_ID_LEN_BASE32) < 0) {
+                    service_id, REND_SERVICE_ID_LEN_BASE32) !=
+      REND_SERVICE_ID_LEN) {
     log_warn(LD_REND, "Could not compute v2 descriptor ID: "
-                      "Illegal characters in service ID: %s",
+                      "Illegal characters or wrong length for service ID: %s",
              safe_str_client(service_id));
     return -1;
   }
diff --git a/src/feature/rend/rendparse.c b/src/feature/rend/rendparse.c
index abd0feb448..a98cb3ad88 100644
--- a/src/feature/rend/rendparse.c
+++ b/src/feature/rend/rendparse.c
@@ -143,8 +143,9 @@ rend_parse_v2_service_descriptor(rend_service_descriptor_t **parsed_out,
     goto err;
   }
   if (base32_decode(desc_id_out, DIGEST_LEN,
-                    tok->args[0], REND_DESC_ID_V2_LEN_BASE32) < 0) {
-    log_warn(LD_REND, "Descriptor ID contains illegal characters: %s",
+                    tok->args[0], REND_DESC_ID_V2_LEN_BASE32) != DIGEST_LEN) {
+    log_warn(LD_REND,
+             "Descriptor ID has wrong length or illegal characters: %s",
              tok->args[0]);
     goto err;
   }
@@ -174,8 +175,10 @@ rend_parse_v2_service_descriptor(rend_service_descriptor_t **parsed_out,
     log_warn(LD_REND, "Invalid secret ID part: '%s'", tok->args[0]);
     goto err;
   }
-  if (base32_decode(secret_id_part, DIGEST_LEN, tok->args[0], 32) < 0) {
-    log_warn(LD_REND, "Secret ID part contains illegal characters: %s",
+  if (base32_decode(secret_id_part, DIGEST_LEN, tok->args[0], 32) !=
+      DIGEST_LEN) {
+    log_warn(LD_REND,
+             "Secret ID part has wrong length or illegal characters: %s",
              tok->args[0]);
     goto err;
   }
@@ -429,8 +432,10 @@ rend_parse_introduction_points(rend_service_descriptor_t *parsed,
     /* Parse identifier. */
     tok = find_by_keyword(tokens, R_IPO_IDENTIFIER);
     if (base32_decode(info->identity_digest, DIGEST_LEN,
-                      tok->args[0], REND_INTRO_POINT_ID_LEN_BASE32) < 0) {
-      log_warn(LD_REND, "Identity digest contains illegal characters: %s",
+                      tok->args[0], REND_INTRO_POINT_ID_LEN_BASE32) !=
+        DIGEST_LEN) {
+      log_warn(LD_REND,
+               "Identity digest has wrong length or illegal characters: %s",
                tok->args[0]);
       rend_intro_point_free(intro);
       goto err;
diff --git a/src/lib/encoding/binascii.c b/src/lib/encoding/binascii.c
index de4d1648bb..187df34243 100644
--- a/src/lib/encoding/binascii.c
+++ b/src/lib/encoding/binascii.c
@@ -84,7 +84,7 @@ base32_encode(char *dest, size_t destlen, const char *src, size_t srclen)
 }
 
 /** Implements base32 decoding as in RFC 4648.
- * Returns 0 if successful, -1 otherwise.
+ * Return the number of bytes decoded if successful; -1 otherwise.
  */
 int
 base32_decode(char *dest, size_t destlen, const char *src, size_t srclen)
@@ -147,7 +147,7 @@ base32_decode(char *dest, size_t destlen, const char *src, size_t srclen)
   memset(tmp, 0, srclen); /* on the heap, this should be safe */
   tor_free(tmp);
   tmp = NULL;
-  return 0;
+  return i;
 }
 
 #define BASE64_OPENSSL_LINELEN 64
diff --git a/src/test/fuzz/fuzz_strops.c b/src/test/fuzz/fuzz_strops.c
index 64a6453050..a37cbb5be8 100644
--- a/src/test/fuzz/fuzz_strops.c
+++ b/src/test/fuzz/fuzz_strops.c
@@ -86,15 +86,13 @@ b16_enc(const chunk_t *inp)
   return ch;
 }
 
-#if 0
 static chunk_t *
 b32_dec(const chunk_t *inp)
 {
   chunk_t *ch = chunk_new(inp->len);//XXXX
   int r = base32_decode((char *)ch->buf, ch->len, (char *)inp->buf, inp->len);
   if (r >= 0) {
-    ch->len = r; // XXXX we need some way to get the actual length of
-                 // XXXX the output here.
+    ch->len = r;
   } else {
     chunk_free(ch);
   }
@@ -108,7 +106,6 @@ b32_enc(const chunk_t *inp)
   ch->len = strlen((char *) ch->buf);
   return ch;
 }
-#endif
 
 static chunk_t *
 b64_dec(const chunk_t *inp)
@@ -222,10 +219,7 @@ fuzz_main(const uint8_t *stdin_buf, size_t data_size)
       ENCODE_ROUNDTRIP(b16_enc, b16_dec, chunk_free_);
       break;
     case 1:
-      /*
-        XXXX see notes above about our base-32 functions.
       ENCODE_ROUNDTRIP(b32_enc, b32_dec, chunk_free_);
-      */
       break;
     case 2:
       ENCODE_ROUNDTRIP(b64_enc, b64_dec, chunk_free_);
diff --git a/src/test/test_crypto.c b/src/test/test_crypto.c
index 0b57448bcf..0903c5c49a 100644
--- a/src/test/test_crypto.c
+++ b/src/test/test_crypto.c
@@ -1703,13 +1703,13 @@ test_crypto_base32_decode(void *arg)
   /* Encode and decode a random string. */
   base32_encode(encoded, 96 + 1, plain, 60);
   res = base32_decode(decoded, 60, encoded, 96);
-  tt_int_op(res,OP_EQ, 0);
+  tt_int_op(res, OP_EQ, 60);
   tt_mem_op(plain,OP_EQ, decoded, 60);
   /* Encode, uppercase, and decode a random string. */
   base32_encode(encoded, 96 + 1, plain, 60);
   tor_strupper(encoded);
   res = base32_decode(decoded, 60, encoded, 96);
-  tt_int_op(res,OP_EQ, 0);
+  tt_int_op(res, OP_EQ, 60);
   tt_mem_op(plain,OP_EQ, decoded, 60);
   /* Change encoded string and decode. */
   if (encoded[0] == 'A' || encoded[0] == 'a')
@@ -1717,12 +1717,12 @@ test_crypto_base32_decode(void *arg)
   else
     encoded[0] = 'A';
   res = base32_decode(decoded, 60, encoded, 96);
-  tt_int_op(res,OP_EQ, 0);
+  tt_int_op(res, OP_EQ, 60);
   tt_mem_op(plain,OP_NE, decoded, 60);
   /* Bad encodings. */
   encoded[0] = '!';
   res = base32_decode(decoded, 60, encoded, 96);
-  tt_int_op(0, OP_GT, res);
+  tt_int_op(res, OP_LT, 0);
 
  done:
   ;
diff --git a/src/test/test_util_format.c b/src/test/test_util_format.c
index 3a0b41faa5..c8945a707c 100644
--- a/src/test/test_util_format.c
+++ b/src/test/test_util_format.c
@@ -346,7 +346,7 @@ test_util_format_base32_decode(void *arg)
     const char *src = "mjwgc2dcnrswqmjs";
 
     ret = base32_decode(dst, strlen(expected), src, strlen(src));
-    tt_int_op(ret, OP_EQ, 0);
+    tt_int_op(ret, OP_EQ, 10);
     tt_str_op(expected, OP_EQ, dst);
   }
 
@@ -357,7 +357,7 @@ test_util_format_base32_decode(void *arg)
     const char *src = "mjwgc2dcnrswq";
 
     ret = base32_decode(dst, strlen(expected), src, strlen(src));
-    tt_int_op(ret, OP_EQ, 0);
+    tt_int_op(ret, OP_EQ, 8);
     tt_mem_op(expected, OP_EQ, dst, strlen(expected));
   }