diff --git a/cbor/CBOR.ml b/cbor/CBOR.ml
deleted file mode 100644
index d57402f..0000000
--- a/cbor/CBOR.ml
+++ /dev/null
@@ -1,228 +0,0 @@
-(** CBOR encoder/decoder, RFC 7049 *)
-
-open Printf
-module BE = EndianBytes.BigEndian_unsafe
-module SE = EndianString.BigEndian_unsafe
-
-exception Error of string
-
-let (@@) f x = f x
-let (|>) x f = f x
-let list_iteri f l = let i = ref 0 in List.iter (fun x -> f !i x; incr i) l
-let fail fmt = ksprintf (fun s -> raise (Error s)) fmt
-
-module Encode = struct
-
-let start () = Buffer.create 10
-
-let init b ~maj add =
-  assert (maj >= 0 && maj < 8);
-  assert (add >= 0 && add < 32);
-  Buffer.add_char b @@ char_of_int @@ (maj lsl 5) lor add
-
-let put_n b n f x =
-  let s = Bytes.create n in
-  f s 0 x;
-  Buffer.add_string b (Bytes.unsafe_to_string s)
-
-let max_uint32 =
-  match Sys.word_size with
-  | 32 -> max_int (* max signed int, but on 32-bit this is enough *)
-  | _ -> int_of_string "0xFF_FF_FF_FF" (* so that it compiles on 32-bit *)
-
-let put b ~maj n =
-  assert (n >= 0);
-  if n < 24 then
-    init b ~maj n
-  else if n < 256 then
-    begin init b ~maj 24; Buffer.add_char b @@ char_of_int n end
-  else if n < 65536 then
-    begin init b ~maj 25; put_n b 2 BE.set_int16 n end
-  else if n <= max_uint32 then
-    begin init b ~maj 26; put_n b 4 BE.set_int32 @@ Int32.of_int n end
-  else
-    begin init b ~maj 27; put_n b 8 BE.set_int64 @@ Int64.of_int n end
-
-let int b n =
-  let (maj,n) = if n < 0 then 1, -1 - n else 0, n in
-  put b ~maj n
-
-let hex_char x =
-  assert (x >= 0 && x < 16);
-  if x <= 9 then Char.chr @@ Char.code '0' + x
-  else Char.chr @@ Char.code 'a' + x - 10
-
-let to_hex s =
-  let r = Bytes.create (String.length s * 2) in
-  for i = 0 to String.length s - 1 do
-    Bytes.set r (i*2) @@ hex_char @@ Char.code s.[i] lsr 4;
-    Bytes.set r (i*2+1) @@ hex_char @@ Char.code s.[i] land 0b1111;
-  done;
-  Bytes.to_string r
-
-end
-
-module Simple = struct
-
-type t =
-[ `Null
-| `Undefined
-| `Simple of int
-| `Bool of bool
-| `Int of int
-| `Float of float
-| `Bytes of string
-| `Text of string
-| `Array of t list
-| `Map of (t * t) list
-]
-
-let encode item =
-  let open Encode in
-  let b = start () in
-  let rec write = function
-  | `Null -> put b ~maj:7 22;
-  | `Undefined -> put b ~maj:7 23;
-  | `Bool false -> put b ~maj:7 20;
-  | `Bool true -> put b ~maj:7 21;
-  | `Simple n when (n >= 0 && n <= 23) || (n >= 32 && n <= 255) -> put b ~maj:7 n
-  | `Simple n -> fail "encode: simple(%d)" n
-  | `Int n -> int b n
-  | `Float f -> init b ~maj:7 27; put_n b 8 BE.set_double f
-  | `Bytes s -> put b ~maj:2 (String.length s); Buffer.add_string b s
-  | `Text s -> put b ~maj:3 (String.length s); Buffer.add_string b s
-  | `Array l -> put b ~maj:4 (List.length l); List.iter write l
-  | `Map m -> put b ~maj:5 (List.length m); List.iter (fun (a,b) -> write a; write b) m
-  in
-  write item;
-  Buffer.contents b
-
-let need (s,i) n =
-  if n > String.length s || !i + n > String.length s then
-    fail "truncated: len %d pos %d need %d" (String.length s) !i n;
-  let j = !i in
-  i := !i + n;
-  j
-
-let get_byte (s,_ as r) = int_of_char @@ s.[need r 1]
-let get_n (s,_ as r) n f = f s @@ need r n
-let get_s (s,_ as r) n = String.sub s (need r n) n
-
-let get_additional byte1 = byte1 land 0b11111
-let is_indefinite byte1 = get_additional byte1 = 31
-
-let int64_max_int = Int64.of_int max_int
-let two_min_int32 = 2 * Int32.to_int Int32.min_int
-
-let extract_number byte1 r =
-  match get_additional byte1 with
-  | n when n < 24 -> n
-  | 24 -> get_byte r
-  | 25 -> get_n r 2 SE.get_uint16
-  | 26 ->
-    let n = Int32.to_int @@ get_n r 4 SE.get_int32 in
-    if n < 0 then n - two_min_int32 else n
-  | 27 ->
-    let n = get_n r 8 SE.get_int64 in
-    if n > int64_max_int || n < 0L then fail "extract_number: %Lu" n;
-    Int64.to_int n
-  | n -> fail "bad additional %d" n
-
-let get_float16 s i =
-  let half = Char.code s.[i] lsl 8 + Char.code s.[i+1] in
-  let mant = half land 0x3ff in
-  let value =
-    match (half lsr 10) land 0x1f with (* exp *)
-    | 31 when mant = 0 -> infinity
-    | 31 -> nan
-    | 0 -> ldexp (float mant) ~-24
-    | exp -> ldexp (float @@ mant + 1024) (exp - 25)
-  in
-  if half land 0x8000 = 0 then value else ~-. value
-
-exception Break
-
-let extract_list byte1 r f =
-  if is_indefinite byte1 then
-    let l = ref [] in
-    try while true do l := f r :: !l done; assert false with Break -> List.rev !l
-  else
-    let n = extract_number byte1 r in Array.to_list @@ Array.init n (fun _ -> f r)
-
-let rec extract_pair r =
-  let a = extract r in
-  let b = try extract r with Break -> fail "extract_pair: unexpected break" in
-  a,b
-and extract_string byte1 r f =
-  if is_indefinite byte1 then
-    let b = Buffer.create 10 in
-    try while true do Buffer.add_string b (f @@ extract r) done; assert false with Break -> Buffer.contents b
-  else
-    let n = extract_number byte1 r in get_s r n
-and extract r =
-  let byte1 = get_byte r in
-  match byte1 lsr 5 with
-  | 0 -> `Int (extract_number byte1 r)
-  | 1 -> `Int (-1 - extract_number byte1 r)
-  | 2 -> `Bytes (extract_string byte1 r (function `Bytes s -> s | _ -> fail "extract: not a bytes chunk"))
-  | 3 -> `Text (extract_string byte1 r (function `Text s -> s | _ -> fail "extract: not a text chunk"))
-  | 4 -> `Array (extract_list byte1 r extract)
-  | 5 -> `Map (extract_list byte1 r extract_pair)
-  | 6 -> let _tag = extract_number byte1 r in extract r
-  | 7 ->
-    begin match get_additional byte1 with
-    | n when n < 20 -> `Simple n
-    | 20 -> `Bool false
-    | 21 -> `Bool true
-    | 22 -> `Null
-    | 23 -> `Undefined
-    | 24 -> `Simple (get_byte r)
-    | 25 -> `Float (get_n r 2 get_float16)
-    | 26 -> `Float (get_n r 4 SE.get_float)
-    | 27 -> `Float (get_n r 8 SE.get_double)
-    | 31 -> raise Break
-    | a -> fail "extract: (7,%d)" a
-    end
-  | _ -> assert false
-
-let decode_partial s =
-  let i = ref 0 in
-  let x = try extract (s,i) with Break -> fail "decode: unexpected break" in
-  x, String.sub s !i (String.length s - !i)
-
-let decode s : t =
-  let x, rest = decode_partial s in
-  if rest = "" then x
-  else fail "decode: extra data: len %d pos %d" (String.length s) (String.length s - String.length rest)
-
-let to_diagnostic item =
-  let b = Buffer.create 10 in
-  let put = Buffer.add_string b in
-  let rec write = function
-  | `Null -> put "null"
-  | `Bool false -> put "false"
-  | `Bool true -> put "true"
-  | `Simple n -> bprintf b "simple(%d)" n
-  | `Undefined -> put "undefined"
-  | `Int n -> bprintf b "%d" n
-  | `Float f ->
-    begin match classify_float f with
-    | FP_nan -> put "NaN"
-    | FP_infinite -> put (if f < 0. then "-Infinity" else "Infinity")
-    | FP_zero | FP_normal | FP_subnormal -> bprintf b "%g" f
-    end
-  | `Bytes s -> bprintf b "h'%s'" (Encode.to_hex s)
-  | `Text s -> bprintf b "\"%s\"" s
-  | `Array l ->
-    put "[";
-    l |> list_iteri (fun i x -> if i <> 0 then put ", "; write x);
-    put "]"
-  | `Map m ->
-    put "{";
-    m |> list_iteri (fun i (k,v) -> if i <> 0 then put ", "; write k; put ": "; write v);
-    put "}"
-  in
-  write item;
-  Buffer.contents b
-
-end (* Simple *)
diff --git a/cbor/CBOR.mli b/cbor/CBOR.mli
deleted file mode 100644
index 4e8f789..0000000
--- a/cbor/CBOR.mli
+++ /dev/null
@@ -1,26 +0,0 @@
-(** CBOR encoder/decoder, RFC 7049 *)
-
-exception Error of string
-
-module Simple : sig
-
-type t =
-[ `Null
-| `Undefined
-| `Simple of int
-| `Bool of bool
-| `Int of int
-| `Float of float
-| `Bytes of string
-| `Text of string
-| `Array of t list
-| `Map of (t * t) list
-]
-
-val encode : t -> string
-val decode : string -> t
-val decode_partial : string -> t * string
-
-val to_diagnostic : t -> string
-
-end
diff --git a/cbor/dune b/cbor/dune
deleted file mode 100644
index e16f80f..0000000
--- a/cbor/dune
+++ /dev/null
@@ -1,5 +0,0 @@
-(library
- (name cbor)
- (public_name webauthn.cbor)
- (wrapped false)
- (libraries ocplib-endian))
diff --git a/src/dune b/src/dune
index 4efe4a7..6b50e81 100644
--- a/src/dune
+++ b/src/dune
@@ -3,4 +3,4 @@
  (public_name webauthn)
  (preprocess
   (pps ppx_deriving_yojson))
- (libraries mirage-crypto-rng yojson mirage-crypto-ec x509 base64 webauthn.cbor))
+ (libraries mirage-crypto-rng yojson mirage-crypto-ec x509 base64 cbor))
diff --git a/webauthn.opam b/webauthn.opam
index f925fae..e0b8835 100644
--- a/webauthn.opam
+++ b/webauthn.opam
@@ -29,6 +29,7 @@ depends: [
   "x509" {>= "0.13.0"}
   "base64" {>= "3.1.0"}
   "cstruct" {>= "6.0.0"}
+  "cbor" {>= "0.5"}
 ]
 
 synopsis: "WebAuthn - authenticating users to services using public key cryptography"