From 55a216bd152e3d270044a890e3d45a928021879e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Thir=C3=A9?=
 <francois.thire@nomadic-labs.com>
Date: Tue, 25 Oct 2022 10:01:43 +0200
Subject: [PATCH 1/5] Dal: Rename parameter 'nb_pages' into 'pages_per_slot'

---
 src/lib_crypto_dal/cryptobox.ml | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/lib_crypto_dal/cryptobox.ml b/src/lib_crypto_dal/cryptobox.ml
index a10c0345851f..5c799f461c0b 100644
--- a/src/lib_crypto_dal/cryptobox.ml
+++ b/src/lib_crypto_dal/cryptobox.ml
@@ -281,7 +281,7 @@ module Inner = struct
     (* Domain for the FFT on erasure encoded slots (as polynomials). *)
     shard_size : int;
     (* Length of a shard in terms of scalar elements. *)
-    nb_pages : int;
+    pages_per_slot : int;
     (* Number of slot pages. *)
     page_length : int;
     remaining_bytes : int;
@@ -381,7 +381,7 @@ module Inner = struct
         domain_2k = make_domain (2 * k);
         domain_n = make_domain n;
         shard_size;
-        nb_pages = slot_size / page_size;
+        pages_per_slot = slot_size / page_size;
         page_length;
         remaining_bytes = page_size mod scalar_bytes_amount;
         evaluations_log;
@@ -412,19 +412,19 @@ module Inner = struct
     else
       let offset = ref 0 in
       let res = Array.init t.k (fun _ -> Scalar.(copy zero)) in
-      for page = 0 to t.nb_pages - 1 do
+      for page = 0 to t.pages_per_slot - 1 do
         for elt = 0 to t.page_length - 1 do
           if !offset > t.slot_size then ()
           else if elt = t.page_length - 1 then (
             let dst = Bytes.create t.remaining_bytes in
             Bytes.blit slot !offset dst 0 t.remaining_bytes ;
             offset := !offset + t.remaining_bytes ;
-            res.((elt * t.nb_pages) + page) <- Scalar.of_bytes_exn dst)
+            res.((elt * t.pages_per_slot) + page) <- Scalar.of_bytes_exn dst)
           else
             let dst = Bytes.create scalar_bytes_amount in
             Bytes.blit slot !offset dst 0 scalar_bytes_amount ;
             offset := !offset + scalar_bytes_amount ;
-            res.((elt * t.nb_pages) + page) <- Scalar.of_bytes_exn dst
+            res.((elt * t.pages_per_slot) + page) <- Scalar.of_bytes_exn dst
         done
       done ;
       Ok res
@@ -436,7 +436,7 @@ module Inner = struct
 
   let eval_coset t eval slot offset page =
     for elt = 0 to t.page_length - 1 do
-      let idx = (elt * t.nb_pages) + page in
+      let idx = (elt * t.pages_per_slot) + page in
       let coeff = Scalar.to_bytes (Array.get eval idx) in
       if elt = t.page_length - 1 then (
         Bytes.blit coeff 0 slot !offset t.remaining_bytes ;
@@ -452,7 +452,7 @@ module Inner = struct
     let eval = Evaluations.(evaluation_fft t.domain_k p |> to_array) in
     let slot = Bytes.init t.slot_size (fun _ -> '0') in
     let offset = ref 0 in
-    for page = 0 to t.nb_pages - 1 do
+    for page = 0 to t.pages_per_slot - 1 do
       eval_coset t eval slot offset page
     done ;
     slot
@@ -803,7 +803,7 @@ module Inner = struct
         ])
 
   let prove_page t p page_index =
-    if page_index < 0 || page_index >= t.nb_pages then
+    if page_index < 0 || page_index >= t.pages_per_slot then
       Error `Segment_index_out_of_range
     else
       let l = 1 lsl Z.(log2up (of_int t.page_length)) in
@@ -813,10 +813,12 @@ module Inner = struct
       in
       Ok (commit t quotient)
 
+  let pages_per_slot t = t.pages_per_slot
+
   (* Parses the [slot_page] to get the evaluations that it contains. The
      evaluation points are given by the [slot_page_index]. *)
   let verify_page t cm {index = slot_page_index; content = slot_page} proof =
-    if slot_page_index < 0 || slot_page_index >= t.nb_pages then
+    if slot_page_index < 0 || slot_page_index >= t.pages_per_slot then
       Error `Segment_index_out_of_range
     else
       let domain = Domains.build ~log:Z.(log2up (of_int t.page_length)) in
-- 
GitLab


From e5723d7c5c8948782df9d4f189fa805cfa8da8cc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Thir=C3=A9?=
 <francois.thire@nomadic-labs.com>
Date: Tue, 25 Oct 2022 10:01:04 +0200
Subject: [PATCH 2/5] Dal: Export the number of pages per slot

---
 src/lib_crypto_dal/cryptobox.ml              | 10 ++++++----
 src/lib_crypto_dal/cryptobox_intf.ml         | 11 +++++++----
 src/lib_protocol_environment/sigs/v8.ml      | 11 +++++++----
 src/lib_protocol_environment/sigs/v8/dal.mli | 11 +++++++----
 4 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/src/lib_crypto_dal/cryptobox.ml b/src/lib_crypto_dal/cryptobox.ml
index 5c799f461c0b..5add41b8f48c 100644
--- a/src/lib_crypto_dal/cryptobox.ml
+++ b/src/lib_crypto_dal/cryptobox.ml
@@ -346,9 +346,13 @@ module Inner = struct
          (req "slot_size" int31)
          (req "number_of_shards" uint16))
 
+  let pages_per_slot {slot_size; page_size; _} = slot_size / page_size
+
   (* Error cases of this functions are not encapsulated into
      `tzresult` for modularity reasons. *)
-  let make {redundancy_factor; slot_size; page_size; number_of_shards} =
+  let make
+      ({redundancy_factor; slot_size; page_size; number_of_shards} as
+      parameters) =
     let open Result_syntax in
     let k = slot_as_polynomial_length ~slot_size in
     let n = redundancy_factor * k in
@@ -381,7 +385,7 @@ module Inner = struct
         domain_2k = make_domain (2 * k);
         domain_n = make_domain n;
         shard_size;
-        pages_per_slot = slot_size / page_size;
+        pages_per_slot = pages_per_slot parameters;
         page_length;
         remaining_bytes = page_size mod scalar_bytes_amount;
         evaluations_log;
@@ -813,8 +817,6 @@ module Inner = struct
       in
       Ok (commit t quotient)
 
-  let pages_per_slot t = t.pages_per_slot
-
   (* Parses the [slot_page] to get the evaluations that it contains. The
      evaluation points are given by the [slot_page_index]. *)
   let verify_page t cm {index = slot_page_index; content = slot_page} proof =
diff --git a/src/lib_crypto_dal/cryptobox_intf.ml b/src/lib_crypto_dal/cryptobox_intf.ml
index 95c0f4fb266c..be90ae7dbc78 100644
--- a/src/lib_crypto_dal/cryptobox_intf.ml
+++ b/src/lib_crypto_dal/cryptobox_intf.ml
@@ -95,10 +95,13 @@ module type VERIFIER = sig
   (** An encoding for the proof of a page. *)
   val page_proof_encoding : page_proof Data_encoding.t
 
-  (** [verify_page t srs commitment page page_proof] returns [Ok
-     true] if the [proof] certifies that the [slot_page] is indeed
-     included in the slot committed with commitment
-     [commitment]. Returns [Ok false] otherwise.
+  (** [pages_per_slot t] returns the number of expected pages per slot. *)
+  val pages_per_slot : parameters -> int
+
+  (** [verify_page t srs commitment page page_proof] returns [Ok true]
+     if the [proof] certifies that the [slot_page] is indeed included
+     in the slot committed with commitment [commitment]. Returns [Ok
+     false] otherwise.
 
       Fails if the index of the page is out of range. *)
   val verify_page :
diff --git a/src/lib_protocol_environment/sigs/v8.ml b/src/lib_protocol_environment/sigs/v8.ml
index 40ed1bd693f8..d2c8b9cb9a00 100644
--- a/src/lib_protocol_environment/sigs/v8.ml
+++ b/src/lib_protocol_environment/sigs/v8.ml
@@ -11961,10 +11961,13 @@ type page_proof
 (** An encoding for the proof of a page. *)
 val page_proof_encoding : page_proof Data_encoding.t
 
-(** [verify_page t commitment page page_proof] returns [Ok
-     true] if the [proof] certifies that the [slot_page] is indeed
-     included in the slot committed with commitment
-     [commitment]. Returns [Ok false] otherwise.
+(** [pages_per_slot t] returns the number of expected pages per slot. *)
+val pages_per_slot : parameters -> int
+
+(** [verify_page t srs commitment page page_proof] returns [Ok true]
+     if the [proof] certifies that the [slot_page] is indeed included
+     in the slot committed with commitment [commitment]. Returns [Ok
+     false] otherwise.
 
       Fails if the index of the page is out of range. *)
 val verify_page :
diff --git a/src/lib_protocol_environment/sigs/v8/dal.mli b/src/lib_protocol_environment/sigs/v8/dal.mli
index a81d669d7c79..911704b38628 100644
--- a/src/lib_protocol_environment/sigs/v8/dal.mli
+++ b/src/lib_protocol_environment/sigs/v8/dal.mli
@@ -89,10 +89,13 @@ type page_proof
 (** An encoding for the proof of a page. *)
 val page_proof_encoding : page_proof Data_encoding.t
 
-(** [verify_page t commitment page page_proof] returns [Ok
-     true] if the [proof] certifies that the [slot_page] is indeed
-     included in the slot committed with commitment
-     [commitment]. Returns [Ok false] otherwise.
+(** [pages_per_slot t] returns the number of expected pages per slot. *)
+val pages_per_slot : parameters -> int
+
+(** [verify_page t srs commitment page page_proof] returns [Ok true]
+     if the [proof] certifies that the [slot_page] is indeed included
+     in the slot committed with commitment [commitment]. Returns [Ok
+     false] otherwise.
 
       Fails if the index of the page is out of range. *)
 val verify_page :
-- 
GitLab


From 378972352909570a569ba289fb8a5bc31390623c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Thir=C3=A9?=
 <francois.thire@nomadic-labs.com>
Date: Tue, 25 Oct 2022 10:02:14 +0200
Subject: [PATCH 3/5] Dal: `verify_segment' now check the length of the page
 content

---
 src/lib_crypto_dal/cryptobox.ml               | 71 ++++++++++---------
 src/lib_crypto_dal/cryptobox_intf.ml          |  6 +-
 .../environment_V7.ml                         | 11 ++-
 src/lib_protocol_environment/sigs/v8.ml       |  8 +--
 src/lib_protocol_environment/sigs/v8/dal.mli  |  8 +--
 src/proto_alpha/lib_protocol/dal_slot_repr.ml |  7 +-
 6 files changed, 65 insertions(+), 46 deletions(-)

diff --git a/src/lib_crypto_dal/cryptobox.ml b/src/lib_crypto_dal/cryptobox.ml
index 5add41b8f48c..73200b2427ff 100644
--- a/src/lib_crypto_dal/cryptobox.ml
+++ b/src/lib_crypto_dal/cryptobox.ml
@@ -823,39 +823,44 @@ module Inner = struct
     if slot_page_index < 0 || slot_page_index >= t.pages_per_slot then
       Error `Segment_index_out_of_range
     else
-      let domain = Domains.build ~log:Z.(log2up (of_int t.page_length)) in
-      let slot_page_evaluations =
-        Array.init
-          (1 lsl Z.(log2up (of_int t.page_length)))
-          (function
-            | i when i < t.page_length - 1 ->
-                let dst = Bytes.create scalar_bytes_amount in
-                Bytes.blit
-                  slot_page
-                  (i * scalar_bytes_amount)
-                  dst
-                  0
-                  scalar_bytes_amount ;
-                Scalar.of_bytes_exn dst
-            | i when i = t.page_length - 1 ->
-                let dst = Bytes.create t.remaining_bytes in
-                Bytes.blit
-                  slot_page
-                  (i * scalar_bytes_amount)
-                  dst
-                  0
-                  t.remaining_bytes ;
-                Scalar.of_bytes_exn dst
-            | _ -> Scalar.(copy zero))
-      in
-      Ok
-        (verify
-           t
-           cm
-           t.srs.kate_amortized_srs_g2_pages
-           domain
-           (Domains.get t.domain_k slot_page_index, slot_page_evaluations)
-           proof)
+      let expected_page_length = t.page_size in
+      let got_page_length = Bytes.length slot_page in
+      if expected_page_length <> got_page_length then
+        Error `Page_length_mismatch
+      else
+        let domain = Domains.build ~log:Z.(log2up (of_int t.page_length)) in
+        let slot_page_evaluations =
+          Array.init
+            (1 lsl Z.(log2up (of_int t.page_length)))
+            (function
+              | i when i < t.page_length - 1 ->
+                  let dst = Bytes.create scalar_bytes_amount in
+                  Bytes.blit
+                    slot_page
+                    (i * scalar_bytes_amount)
+                    dst
+                    0
+                    scalar_bytes_amount ;
+                  Scalar.of_bytes_exn dst
+              | i when i = t.page_length - 1 ->
+                  let dst = Bytes.create t.remaining_bytes in
+                  Bytes.blit
+                    slot_page
+                    (i * scalar_bytes_amount)
+                    dst
+                    0
+                    t.remaining_bytes ;
+                  Scalar.of_bytes_exn dst
+              | _ -> Scalar.(copy zero))
+        in
+        Ok
+          (verify
+             t
+             cm
+             t.srs.kate_amortized_srs_g2_pages
+             domain
+             (Domains.get t.domain_k slot_page_index, slot_page_evaluations)
+             proof)
 end
 
 include Inner
diff --git a/src/lib_crypto_dal/cryptobox_intf.ml b/src/lib_crypto_dal/cryptobox_intf.ml
index be90ae7dbc78..d7bd0d814274 100644
--- a/src/lib_crypto_dal/cryptobox_intf.ml
+++ b/src/lib_crypto_dal/cryptobox_intf.ml
@@ -103,11 +103,13 @@ module type VERIFIER = sig
      in the slot committed with commitment [commitment]. Returns [Ok
      false] otherwise.
 
-      Fails if the index of the page is out of range. *)
+      Fails if the index of the page is out of range or if the page is
+     not of the expected length [page_size] given for the
+     initialisation of [t]. *)
   val verify_page :
     t ->
     commitment ->
     page ->
     page_proof ->
-    (bool, [> `Segment_index_out_of_range]) Result.t
+    (bool, [> `Segment_index_out_of_range | `Page_length_mismatch]) Result.t
 end
diff --git a/src/lib_protocol_environment/environment_V7.ml b/src/lib_protocol_environment/environment_V7.ml
index b77c5e9c06c7..4f6d306d9952 100644
--- a/src/lib_protocol_environment/environment_V7.ml
+++ b/src/lib_protocol_environment/environment_V7.ml
@@ -1398,5 +1398,14 @@ struct
 
   module Equality_witness = Environment_context.Equality_witness
   module Plonk = Tezos_protocol_environment_structs.V7.Plonk
-  module Dal = Tezos_crypto_dal.Cryptobox.Verifier
+
+  module Dal = struct
+    include Tezos_crypto_dal.Cryptobox.Verifier
+
+    let verify_page t sh page proof =
+      match verify_page t sh page proof with
+      | Error `Page_length_mismatch -> Ok false
+      | Error `Segment_index_out_of_range -> Error `Segment_index_out_of_range
+      | Ok r -> Ok r
+  end
 end
diff --git a/src/lib_protocol_environment/sigs/v8.ml b/src/lib_protocol_environment/sigs/v8.ml
index d2c8b9cb9a00..04e45ef17d3a 100644
--- a/src/lib_protocol_environment/sigs/v8.ml
+++ b/src/lib_protocol_environment/sigs/v8.ml
@@ -11969,15 +11969,15 @@ val pages_per_slot : parameters -> int
      in the slot committed with commitment [commitment]. Returns [Ok
      false] otherwise.
 
-      Fails if the index of the page is out of range. *)
+      Fails if the index of the page is out of range or if the page is
+     not of the expected length [page_size] given for the
+     initialisation of [t]. *)
 val verify_page :
   t ->
   commitment ->
   page ->
   page_proof ->
-  ( bool,
-    [> `Degree_exceeds_srs_length of string | `Segment_index_out_of_range] )
-  Result.t
+  (bool, [> `Segment_index_out_of_range | `Page_length_mismatch]) Result.t
 end
 # 136 "v8.in.ml"
 
diff --git a/src/lib_protocol_environment/sigs/v8/dal.mli b/src/lib_protocol_environment/sigs/v8/dal.mli
index 911704b38628..b8a7d918e6aa 100644
--- a/src/lib_protocol_environment/sigs/v8/dal.mli
+++ b/src/lib_protocol_environment/sigs/v8/dal.mli
@@ -97,12 +97,12 @@ val pages_per_slot : parameters -> int
      in the slot committed with commitment [commitment]. Returns [Ok
      false] otherwise.
 
-      Fails if the index of the page is out of range. *)
+      Fails if the index of the page is out of range or if the page is
+     not of the expected length [page_size] given for the
+     initialisation of [t]. *)
 val verify_page :
   t ->
   commitment ->
   page ->
   page_proof ->
-  ( bool,
-    [> `Degree_exceeds_srs_length of string | `Segment_index_out_of_range] )
-  Result.t
+  (bool, [> `Segment_index_out_of_range | `Page_length_mismatch]) Result.t
diff --git a/src/proto_alpha/lib_protocol/dal_slot_repr.ml b/src/proto_alpha/lib_protocol/dal_slot_repr.ml
index 7448c9ce5a60..9a23410edc33 100644
--- a/src/proto_alpha/lib_protocol/dal_slot_repr.ml
+++ b/src/proto_alpha/lib_protocol/dal_slot_repr.ml
@@ -631,9 +631,12 @@ module History = struct
             "Wrong page content for the given page index and slot commitment"
       | Error `Segment_index_out_of_range ->
           fail_with_error_msg "Segment_index_out_of_range"
-      | Error (`Degree_exceeds_srs_length s) ->
+      | Error `Page_length_mismatch ->
           fail_with_error_msg
-          @@ Format.sprintf "Degree_exceeds_srs_length: %s" s
+          @@ Format.sprintf
+               "Page_length_mismatch: Expected:%d. Got: %d"
+               dal_params.page_size
+               (Bytes.length page.content)
 
     let produce_proof dal_params page_id ~page_info slots_hist hist_cache =
       let open Lwt_tzresult_syntax in
-- 
GitLab


From 9f7eefef5ae4fe9989adb0d246e709e362886458 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Thir=C3=A9?=
 <francois.thire@nomadic-labs.com>
Date: Tue, 25 Oct 2022 13:50:57 +0200
Subject: [PATCH 4/5] Dal: Export a parameter function

---
 src/lib_crypto_dal/cryptobox.ml              | 12 ++++--------
 src/lib_crypto_dal/cryptobox.mli             |  3 ---
 src/lib_crypto_dal/cryptobox_intf.ml         |  4 ++++
 src/lib_protocol_environment/sigs/v8.ml      |  4 ++++
 src/lib_protocol_environment/sigs/v8/dal.mli |  4 ++++
 5 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/lib_crypto_dal/cryptobox.ml b/src/lib_crypto_dal/cryptobox.ml
index 73200b2427ff..0651cfd3335b 100644
--- a/src/lib_crypto_dal/cryptobox.ml
+++ b/src/lib_crypto_dal/cryptobox.ml
@@ -396,6 +396,10 @@ module Inner = struct
     in
     ensure_validity t
 
+  let parameters
+      ({redundancy_factor; slot_size; page_size; number_of_shards; _} : t) =
+    {redundancy_factor; slot_size; page_size; number_of_shards}
+
   let polynomial_degree = Polynomials.degree
 
   let polynomial_evaluate = Polynomials.evaluate
@@ -878,12 +882,4 @@ module Internal_for_tests = struct
     {srs_g1; srs_g2}
 
   let load_parameters parameters = initialisation_parameters := Some parameters
-
-  let parameters (t : t) =
-    {
-      redundancy_factor = t.redundancy_factor;
-      slot_size = t.slot_size;
-      page_size = t.page_size;
-      number_of_shards = t.number_of_shards;
-    }
 end
diff --git a/src/lib_crypto_dal/cryptobox.mli b/src/lib_crypto_dal/cryptobox.mli
index 37c8e2b53178..afa68d7049ac 100644
--- a/src/lib_crypto_dal/cryptobox.mli
+++ b/src/lib_crypto_dal/cryptobox.mli
@@ -218,7 +218,4 @@ module Internal_for_tests : sig
      from test frameworks where tests with various parameters could be
      run using the same binary. *)
   val load_parameters : initialisation_parameters -> unit
-
-  (** [parameters t] returns the parameters with which [t] was initialized. *)
-  val parameters : t -> parameters
 end
diff --git a/src/lib_crypto_dal/cryptobox_intf.ml b/src/lib_crypto_dal/cryptobox_intf.ml
index d7bd0d814274..825bc4f002ef 100644
--- a/src/lib_crypto_dal/cryptobox_intf.ml
+++ b/src/lib_crypto_dal/cryptobox_intf.ml
@@ -65,6 +65,10 @@ module type VERIFIER = sig
     primitives defined in this module and stores them in a value of type [t] *)
   val make : parameters -> (t, [> `Fail of string]) result
 
+  (** [parameters t] returns the parameters given when [t] was
+     initialised with the function {!val:make} *)
+  val parameters : t -> parameters
+
   (** Commitment to a polynomial. *)
   type commitment
 
diff --git a/src/lib_protocol_environment/sigs/v8.ml b/src/lib_protocol_environment/sigs/v8.ml
index 04e45ef17d3a..e494e59c5432 100644
--- a/src/lib_protocol_environment/sigs/v8.ml
+++ b/src/lib_protocol_environment/sigs/v8.ml
@@ -11913,6 +11913,10 @@ val parameters_encoding : parameters Data_encoding.t
   defined in this module and store them in a value of type [t] *)
 val make : parameters -> (t, [> `Fail of string]) result
 
+(** [parameters t] returns the parameters given when [t] was
+     initialised with the function {!val:make} *)
+val parameters : t -> parameters
+
 (** Commitment to a polynomial. *)
 type commitment
 
diff --git a/src/lib_protocol_environment/sigs/v8/dal.mli b/src/lib_protocol_environment/sigs/v8/dal.mli
index b8a7d918e6aa..7950e6e1ea20 100644
--- a/src/lib_protocol_environment/sigs/v8/dal.mli
+++ b/src/lib_protocol_environment/sigs/v8/dal.mli
@@ -41,6 +41,10 @@ val parameters_encoding : parameters Data_encoding.t
   defined in this module and store them in a value of type [t] *)
 val make : parameters -> (t, [> `Fail of string]) result
 
+(** [parameters t] returns the parameters given when [t] was
+     initialised with the function {!val:make} *)
+val parameters : t -> parameters
+
 (** Commitment to a polynomial. *)
 type commitment
 
-- 
GitLab


From 20e5bf406af9204d1b2245c70cb2fa8b93a0fade Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Thir=C3=A9?=
 <francois.thire@nomadic-labs.com>
Date: Tue, 25 Oct 2022 14:19:28 +0200
Subject: [PATCH 5/5] Protocol/DAL: use pages_per_slot

---
 .../bin_sc_rollup_node/dal_slots_tracker.ml   |  2 +-
 .../lib_parameters/default_parameters.ml      |  4 +--
 src/proto_alpha/lib_protocol/alpha_context.ml |  2 ++
 .../lib_protocol/alpha_context.mli            | 16 ++++++----
 src/proto_alpha/lib_protocol/dal_slot_repr.ml | 20 ++++++------
 .../lib_protocol/dal_slot_repr.mli            | 32 ++++++++++---------
 .../lib_protocol/test/helpers/dal_helpers.ml  |  4 +--
 7 files changed, 44 insertions(+), 36 deletions(-)

diff --git a/src/proto_alpha/bin_sc_rollup_node/dal_slots_tracker.ml b/src/proto_alpha/bin_sc_rollup_node/dal_slots_tracker.ml
index f988042e4372..eabf13ed0045 100644
--- a/src/proto_alpha/bin_sc_rollup_node/dal_slots_tracker.ml
+++ b/src/proto_alpha/bin_sc_rollup_node/dal_slots_tracker.ml
@@ -230,7 +230,7 @@ let download_and_save_slots
     @@ Bitset.inter subscribed_slots_indexes confirmed_slots_indexes
   in
   let params = protocol_constants.parametric.dal.cryptobox_parameters in
-  let number_of_pages = params.slot_size / params.page_size in
+  let number_of_pages = Dal.Page.pages_per_slot params in
   (* DAL/FIXME: https://gitlab.com/tezos/tezos/-/issues/2766.
      As part of the clean rollup storage workflow, we should make sure that
      pages for old slots are removed from the storage when not needed anymore.
diff --git a/src/proto_alpha/lib_parameters/default_parameters.ml b/src/proto_alpha/lib_parameters/default_parameters.ml
index 629fd3e63e80..91041cab3b54 100644
--- a/src/proto_alpha/lib_parameters/default_parameters.ml
+++ b/src/proto_alpha/lib_parameters/default_parameters.ml
@@ -60,7 +60,7 @@ let sc_rollup_timeout_period_in_blocks = 20_160
    Think harder about those values. *)
 let default_cryptobox_parameters =
   {
-    Dal.Slots_history.page_size = 4096;
+    Dal.page_size = 4096;
     slot_size = 1 lsl 20;
     redundancy_factor = 16;
     number_of_shards = 2048;
@@ -276,7 +276,7 @@ let constants_mainnet =
 let derive_cryptobox_parameters ~redundancy_factor ~mainnet_constants_divider =
   let m = default_cryptobox_parameters in
   {
-    Dal.Slots_history.redundancy_factor;
+    Dal.redundancy_factor;
     page_size = m.page_size / mainnet_constants_divider;
     slot_size = m.slot_size / mainnet_constants_divider;
     number_of_shards = m.number_of_shards / mainnet_constants_divider;
diff --git a/src/proto_alpha/lib_protocol/alpha_context.ml b/src/proto_alpha/lib_protocol/alpha_context.ml
index 1edf9aa6825f..2e60209824c1 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.ml
+++ b/src/proto_alpha/lib_protocol/alpha_context.ml
@@ -97,6 +97,8 @@ module Sc_rollup = struct
 end
 
 module Dal = struct
+  include Dal_slot_repr
+
   module Slot_index = struct
     include Dal_slot_repr.Index
   end
diff --git a/src/proto_alpha/lib_protocol/alpha_context.mli b/src/proto_alpha/lib_protocol/alpha_context.mli
index f04a6959c5d8..8c838787e522 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.mli
+++ b/src/proto_alpha/lib_protocol/alpha_context.mli
@@ -2782,6 +2782,13 @@ end
 
 (** This module exposes definitions for the data-availability layer. *)
 module Dal : sig
+  type parameters = Dal.parameters = {
+    redundancy_factor : int;
+    page_size : int;
+    slot_size : int;
+    number_of_shards : int;
+  }
+
   (** This module re-exports definitions from {!Dal_slot_repr.Index}. *)
   module Slot_index : sig
     type t
@@ -2822,6 +2829,8 @@ module Dal : sig
   module Page : sig
     type content = bytes
 
+    val pages_per_slot : parameters -> int
+
     module Index : sig
       type t = int
 
@@ -2904,13 +2913,6 @@ module Dal : sig
       Slot.Header.t list ->
       (t * History_cache.t) tzresult
 
-    type dal_parameters = Dal.parameters = {
-      redundancy_factor : int;
-      page_size : int;
-      slot_size : int;
-      number_of_shards : int;
-    }
-
     type proof
   end
 
diff --git a/src/proto_alpha/lib_protocol/dal_slot_repr.ml b/src/proto_alpha/lib_protocol/dal_slot_repr.ml
index 9a23410edc33..bb7d89917a92 100644
--- a/src/proto_alpha/lib_protocol/dal_slot_repr.ml
+++ b/src/proto_alpha/lib_protocol/dal_slot_repr.ml
@@ -23,6 +23,15 @@
 (*                                                                           *)
 (*****************************************************************************)
 
+type parameters = Dal.parameters = {
+  redundancy_factor : int;
+  page_size : int;
+  slot_size : int;
+  number_of_shards : int;
+}
+
+let parameters_encoding = Dal.parameters_encoding
+
 module Commitment = struct
   (* DAL/FIXME https://gitlab.com/tezos/tezos/-/issues/3389
 
@@ -120,6 +129,8 @@ module Page = struct
 
   type slot_index = Index.t
 
+  let pages_per_slot = Dal.pages_per_slot
+
   module Index = struct
     type t = int
 
@@ -586,15 +597,6 @@ module History = struct
             pp_inclusion_proof
             next_inc_proof
 
-    type dal_parameters = Dal.parameters = {
-      redundancy_factor : int;
-      page_size : int;
-      slot_size : int;
-      number_of_shards : int;
-    }
-
-    let dal_parameters_encoding = Dal.parameters_encoding
-
     type error += Dal_proof_error of string
 
     let () =
diff --git a/src/proto_alpha/lib_protocol/dal_slot_repr.mli b/src/proto_alpha/lib_protocol/dal_slot_repr.mli
index cb39a47ea04c..a17d2d713a2a 100644
--- a/src/proto_alpha/lib_protocol/dal_slot_repr.mli
+++ b/src/proto_alpha/lib_protocol/dal_slot_repr.mli
@@ -23,6 +23,19 @@
 (*                                                                           *)
 (*****************************************************************************)
 
+(** To verify the proof of a page membership in its associated slot, the
+     Cryptobox module needs the following Dal parameters. These are part of the
+     protocol's parameters. See {!Default_parameters.default_dal}. *)
+type parameters = Dal.parameters = {
+  redundancy_factor : int;
+  page_size : int;
+  slot_size : int;
+  number_of_shards : int;
+}
+
+(** An encoding for values of type {!parameters}. *)
+val parameters_encoding : parameters Data_encoding.t
+
 (** Slot header representation for the data-availability layer.
 
     {1 Overview}
@@ -109,6 +122,8 @@ module Page : sig
 
   type slot_index = Index.t
 
+  val pages_per_slot : Dal.parameters -> int
+
   module Index : sig
     type t = int
 
@@ -242,19 +257,6 @@ module History : sig
   (** Pretty-printer for {!proof}. *)
   val pp_proof : Format.formatter -> proof -> unit
 
-  (** To verify the proof of a page membership in its associated slot, the
-     Cryptobox module needs the following Dal parameters. These are part of the
-     protocol's parameters. See {!Default_parameters.default_dal}. *)
-  type dal_parameters = Dal.parameters = {
-    redundancy_factor : int;
-    page_size : int;
-    slot_size : int;
-    number_of_shards : int;
-  }
-
-  (** An encoding for values of type {!dal_parameters}. *)
-  val dal_parameters_encoding : dal_parameters Data_encoding.t
-
   (** [produce_proof dal_parameters page_id page_info slots_hist hist_cache]
       produces a proof that either:
       - there exists a confirmed slot in the skip list that contains
@@ -273,7 +275,7 @@ module History : sig
       the candidate slot (if any).
   *)
   val produce_proof :
-    dal_parameters ->
+    parameters ->
     Page.t ->
     page_info:(Page.content * Page.proof) option ->
     t ->
@@ -291,7 +293,7 @@ module History : sig
       the candidate slot (if any).
   *)
   val verify_proof :
-    dal_parameters -> Page.t -> t -> proof -> Page.content option tzresult Lwt.t
+    parameters -> Page.t -> t -> proof -> Page.content option tzresult Lwt.t
 
   type error += Add_element_in_slots_skip_list_violates_ordering
 
diff --git a/src/proto_alpha/lib_protocol/test/helpers/dal_helpers.ml b/src/proto_alpha/lib_protocol/test/helpers/dal_helpers.ml
index d833c46adca5..221181ef6b0d 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/dal_helpers.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/dal_helpers.ml
@@ -49,7 +49,7 @@ let mk_cryptobox dal_params =
   let open Result_syntax in
   let parameters =
     Cryptobox.Internal_for_tests.initialisation_parameters_from_slot_size
-      ~slot_size:dal_params.Hist.slot_size
+      ~slot_size:dal_params.S.slot_size
   in
   let () = Cryptobox.Internal_for_tests.load_parameters parameters in
   match Cryptobox.make dal_params with
@@ -59,7 +59,7 @@ let mk_cryptobox dal_params =
 let derive_dal_parameters (reference : Cryptobox.parameters) ~redundancy_factor
     ~constants_divider =
   {
-    Hist.redundancy_factor;
+    S.redundancy_factor;
     page_size = reference.page_size / constants_divider;
     slot_size = reference.slot_size / constants_divider;
     number_of_shards = reference.number_of_shards / constants_divider;
-- 
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