diff --git a/src/proto_alpha/lib_delegate/baking_actions.ml b/src/proto_alpha/lib_delegate/baking_actions.ml
index 48ca71b4086b17fe653b85db7d9dd30d4b79acd8..614603b688a6ae1476880cf0349bc937f97b4138 100644
--- a/src/proto_alpha/lib_delegate/baking_actions.ml
+++ b/src/proto_alpha/lib_delegate/baking_actions.ml
@@ -30,6 +30,42 @@ module Events = Baking_events.Actions
 
 module Profiler = (val Profiler.wrap Baking_profiler.baker_profiler)
 
+type error +=
+  | Unexpected_signature_type of Signature.t
+  | Missing_bls_companion_key_for_dal of Baking_state.Key.t
+
+let () =
+  register_error_kind
+    `Permanent
+    ~id:"Baking_actions.unexpected_signature_type"
+    ~title:"Unexpected signature type"
+    ~description:"Signature should be a BLS signature."
+    ~pp:(fun ppf s ->
+      Format.fprintf
+        ppf
+        "Signature should be a BLS signature %a."
+        Signature.pp
+        s)
+    Data_encoding.(obj1 (req "signature" Signature.encoding))
+    (function Unexpected_signature_type s -> Some s | _ -> None)
+    (fun s -> Unexpected_signature_type s) ;
+  register_error_kind
+    `Permanent
+    ~id:"Baking_actions.Missing_bls_companion_key_for_dal"
+    ~title:"Missing a BLS companion key for DAL attestations"
+    ~description:
+      "The consensus key is a BLS key but is missing a companion key, so it \
+       cannot sign a DAL attestation."
+    ~pp:(fun ppf s ->
+      Format.fprintf
+        ppf
+        "Expected a BLS companion key for the consensus key %a."
+        Baking_state.Key.pp
+        s)
+    Data_encoding.(obj1 (req "consensus_key" Baking_state.Key.encoding))
+    (function Missing_bls_companion_key_for_dal ck -> Some ck | _ -> None)
+    (fun ck -> Missing_bls_companion_key_for_dal ck)
+
 module Operations_source = struct
   type error +=
     | Failed_operations_fetch of {
@@ -690,16 +726,60 @@ let forge_and_sign_consensus_vote global_state ~branch unsigned_consensus_vote :
   let unsigned_operation_bytes =
     Data_encoding.Binary.to_bytes_exn encoding unsigned_operation
   in
-  let sk_uri = delegate.consensus_key.secret_key_uri in
-  let* signature =
+  let sk_consensus_uri = delegate.consensus_key.secret_key_uri in
+  let* consensus_sig =
     sign
       ?timeout:global_state.config.remote_calls_timeout
       ~signing_request
       cctxt
       ~watermark
-      sk_uri
+      sk_consensus_uri
       unsigned_operation_bytes
   in
+  let* signature =
+    if not bls_mode then return consensus_sig
+    else
+      match dal_content with
+      | None -> return consensus_sig
+      | Some {attestation = dal_attestation} -> (
+          let* companion_key =
+            match delegate.companion_key with
+            | None ->
+                tzfail
+                  (Missing_bls_companion_key_for_dal delegate.consensus_key)
+            | Some companion_key -> return companion_key
+          in
+          let sk_companion_uri = companion_key.secret_key_uri in
+          let* companion_sig =
+            sign
+              ?timeout:global_state.config.remote_calls_timeout
+              ~signing_request
+              cctxt
+              ~watermark
+              sk_companion_uri
+              unsigned_operation_bytes
+          in
+          match (consensus_sig, companion_sig) with
+          (* This if-else branch is for BLS mode so both signatures
+             should be BLS signatures *)
+          | Signature.Bls consensus_sig, Signature.Bls companion_sig -> (
+              let dal_dependent_bls_sig_opt =
+                Alpha_context.Dal.Attestation.Dal_dependent_signing
+                .aggregate_sig
+                  ~subgroup_check:false
+                  ~consensus_sig
+                  ~companion_sig
+                  dal_attestation
+              in
+              match dal_dependent_bls_sig_opt with
+              | None -> tzfail Baking_errors.Signature_aggregation_failure
+              | Some dal_dependent_bls_sig_opt ->
+                  return (Signature.Bls dal_dependent_bls_sig_opt : Signature.t)
+              )
+          | Signature.Bls _, _ ->
+              tzfail (Unexpected_signature_type companion_sig)
+          | _ -> tzfail (Unexpected_signature_type consensus_sig))
+  in
   let protocol_data = Operation_data {contents; signature = Some signature} in
   let signed_operation : Operation.packed = {shell; protocol_data} in
   return {unsigned_consensus_vote; signed_operation}
diff --git a/src/proto_alpha/lib_delegate/baking_errors.ml b/src/proto_alpha/lib_delegate/baking_errors.ml
index 1ebc51e5a8f6743474c10e105c95bf60c5ffebea..ff0dccdc812cc7a3a3b6796e477b69165bfdd61b 100644
--- a/src/proto_alpha/lib_delegate/baking_errors.ml
+++ b/src/proto_alpha/lib_delegate/baking_errors.ml
@@ -435,3 +435,17 @@ let () =
     Data_encoding.unit
     (function Incompatible_dal_options -> Some () | _ -> None)
     (fun () -> Incompatible_dal_options)
+
+(* BLS related errors *)
+type error += Signature_aggregation_failure
+
+let () =
+  register_error_kind
+    `Permanent
+    ~id:"baker.signature_aggregation_failure"
+    ~title:"Signature aggregation failure"
+    ~description:"Signature aggregation failed."
+    ~pp:(fun ppf () -> Format.fprintf ppf "Signature aggregation failed.")
+    Data_encoding.unit
+    (function Signature_aggregation_failure -> Some () | _ -> None)
+    (fun () -> Signature_aggregation_failure)
diff --git a/src/proto_alpha/lib_delegate/block_forge.ml b/src/proto_alpha/lib_delegate/block_forge.ml
index 102fd897253bb90d6020639e8064e6bd325d0c0b..7e3531ce1c87eeeebd7a34f0b51f5a0470abfa30 100644
--- a/src/proto_alpha/lib_delegate/block_forge.ml
+++ b/src/proto_alpha/lib_delegate/block_forge.ml
@@ -26,19 +26,6 @@
 open Protocol
 open Alpha_context
 
-type error += Signature_aggregation_failure
-
-let () =
-  register_error_kind
-    `Permanent
-    ~id:"Block_forge.signature_aggregation_failure"
-    ~title:"Signature aggregation failure"
-    ~description:"Signature aggregation failed."
-    ~pp:(fun ppf () -> Format.fprintf ppf "Signature aggregation failed.")
-    Data_encoding.unit
-    (function Signature_aggregation_failure -> Some () | _ -> None)
-    (fun () -> Signature_aggregation_failure)
-
 type unsigned_block = {
   unsigned_block_header : Block_header.t;
   operations : Tezos_base.Operation.t list list;
@@ -449,7 +436,7 @@ let aggregate_attestations eligible_attestations =
           in
           let protocol_data = {contents; signature = Some (Bls signature)} in
           return (Some {shell; protocol_data = Operation_data protocol_data})
-      | None -> tzfail Signature_aggregation_failure)
+      | None -> tzfail Baking_errors.Signature_aggregation_failure)
 
 (* [partition_consensus_operations_on_proposal operations] partitions consensus
    operations as follows :
@@ -578,7 +565,7 @@ let aggregate_attestations_on_reproposal consensus_operations =
             {shell; protocol_data = Operation_data protocol_data}
           in
           return (attestations_aggregate :: other_operations)
-      | None -> tzfail Signature_aggregation_failure)
+      | None -> tzfail Baking_errors.Signature_aggregation_failure)
 
 (* [forge] a new [unsigned_block] in accordance with [simulation_kind] and
    [simulation_mode] *)
diff --git a/src/proto_alpha/lib_protocol/alpha_context.mli b/src/proto_alpha/lib_protocol/alpha_context.mli
index 4a43e54b22afd463467dd2e30ad6b25c4a1015f4..89880e76062638462c6bb0617bdace4ee321abe4 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.mli
+++ b/src/proto_alpha/lib_protocol/alpha_context.mli
@@ -2878,6 +2878,24 @@ module Dal : sig
     val record_attestation : context -> tb_slot:Slot.t -> t -> context
 
     val attestations : context -> t Slot.Map.t
+
+    module Dal_dependent_signing : sig
+      (** See {!Dal_attestation_repr.Dal_dependent_signing.aggregate_pk}. *)
+      val aggregate_pk :
+        subgroup_check:bool ->
+        consensus_pk:Bls.Public_key.t ->
+        companion_pk:Bls.Public_key.t ->
+        t ->
+        Bls.Public_key.t option
+
+      (** See {!Dal_attestation_repr.Dal_dependent_signing.aggregate_sig}. *)
+      val aggregate_sig :
+        subgroup_check:bool ->
+        consensus_sig:Bls.t ->
+        companion_sig:Bls.t ->
+        t ->
+        Bls.t option
+    end
   end
 
   type slot_id = {published_level : Raw_level.t; index : Slot_index.t}
diff --git a/src/proto_alpha/lib_protocol/dal_attestation_repr.ml b/src/proto_alpha/lib_protocol/dal_attestation_repr.ml
index 0daa88ff0fd3ff2a69825673b9a87ac963c5d749..5c9375180b3c745155b80cb9222a238a57054f64 100644
--- a/src/proto_alpha/lib_protocol/dal_attestation_repr.ml
+++ b/src/proto_alpha/lib_protocol/dal_attestation_repr.ml
@@ -47,6 +47,8 @@ let encoding = Bitset.encoding
 
 let empty = Bitset.empty
 
+let to_z = Bitset.to_z
+
 let is_attested t index =
   let open Dal_slot_index_repr in
   match Bitset.mem t (to_int index) with
@@ -175,3 +177,46 @@ module Accountability = struct
       total_shards = number_of_shards;
     }
 end
+
+module Dal_dependent_signing = struct
+  (* Computes [((to_z t) + 1) * companion + consensus].
+
+     The purpose of the [+ 1] is to guarantee that the result is
+     different from [consensus], even when [t] is {!empty} (because
+     dal is optional in attestations, and attestations without dal are
+     signed with just the consensus key).
+
+     Produces the same result but is faster than calling
+     [aggregate_weighted_opt
+       [((to_z t) + 1, companion); (Z.one, consensus)]]. *)
+  let aggregate ~subgroup_check ~aggregate_opt ~aggregate_weighted_opt
+      ~consensus ~companion t =
+    let subgroup_check = Some subgroup_check in
+    let z = Z.succ (to_z t) in
+    let weighted_companion_opt =
+      if Z.equal z Z.one then
+        (* Small optimization for the [t = empty] case. *)
+        Some companion
+      else aggregate_weighted_opt ?subgroup_check [(z, companion)]
+    in
+    Option.bind weighted_companion_opt (fun weighted_companion ->
+        aggregate_opt ?subgroup_check [weighted_companion; consensus])
+
+  let aggregate_pk ~subgroup_check ~consensus_pk ~companion_pk t =
+    aggregate
+      ~subgroup_check
+      ~aggregate_opt:Bls.aggregate_public_key_opt
+      ~aggregate_weighted_opt:Bls.aggregate_public_key_weighted_opt
+      ~consensus:consensus_pk
+      ~companion:companion_pk
+      t
+
+  let aggregate_sig ~subgroup_check ~consensus_sig ~companion_sig t =
+    aggregate
+      ~subgroup_check
+      ~aggregate_opt:Bls.aggregate_signature_opt
+      ~aggregate_weighted_opt:Bls.aggregate_signature_weighted_opt
+      ~consensus:consensus_sig
+      ~companion:companion_sig
+      t
+end
diff --git a/src/proto_alpha/lib_protocol/dal_attestation_repr.mli b/src/proto_alpha/lib_protocol/dal_attestation_repr.mli
index 06d59da6dd1a29d88cd01248bbd115c18e451272..6ef9b54fad05db5f9328f357c1333db3214986af 100644
--- a/src/proto_alpha/lib_protocol/dal_attestation_repr.mli
+++ b/src/proto_alpha/lib_protocol/dal_attestation_repr.mli
@@ -137,3 +137,34 @@ module Accountability : sig
     Dal_slot_index_repr.t ->
     attestation_status
 end
+
+(** {!type-t}-dependent combination of public keys or signatures. *)
+module Dal_dependent_signing : sig
+  (** Encodes the {!type-t} argument into a specific combination of
+      [consensus_pk] and [companion_pk].
+
+      If [subgroup_check] is set, also checks whether the points are
+      in the appropriate subgroup.
+
+      Returns [None] if the deserialization of points fails or the
+      subgroup check fails -- this cannot happen when the provided
+      keys are valid BLS keys.
+
+      Guarantees that the resulting key is different from both
+      [consensus_pk] and [companion_pk]. *)
+  val aggregate_pk :
+    subgroup_check:bool ->
+    consensus_pk:Bls.Public_key.t ->
+    companion_pk:Bls.Public_key.t ->
+    t ->
+    Bls.Public_key.t option
+
+  (** Computes the same {!type-t}-dependent combination as
+      {!aggregate_pk}, but with signatures instead of public keys. *)
+  val aggregate_sig :
+    subgroup_check:bool ->
+    consensus_sig:Bls.t ->
+    companion_sig:Bls.t ->
+    t ->
+    Bls.t option
+end
diff --git a/src/proto_alpha/lib_protocol/validate.ml b/src/proto_alpha/lib_protocol/validate.ml
index 0c2f8be7e326d9069d90e83f064345df52a03003..137079c75d4d3c9d0d1e32b64fe81ab97c691d5c 100644
--- a/src/proto_alpha/lib_protocol/validate.ml
+++ b/src/proto_alpha/lib_protocol/validate.ml
@@ -826,12 +826,52 @@ module Consensus = struct
         dal_content
     in
     let*? () =
+      let open Result_syntax in
       if check_signature then
-        Operation.check_signature
-          vi.ctxt
-          consensus_key.consensus_pk
-          vi.chain_id
-          operation
+        let* dal_dependent_pk =
+          match (consensus_key.Consensus_key.consensus_pk, dal_content) with
+          | Bls consensus_bls_pk, Some {attestation = dal_attestation}
+            when Constants.aggregate_attestation vi.ctxt -> (
+              match consensus_key.companion_pk with
+              | None ->
+                  tzfail
+                    (Missing_companion_key_for_bls_dal
+                       (Consensus_key.pkh consensus_key))
+              | Some companion_pk -> (
+                  let dal_dependent_bls_pk_opt =
+                    Dal.Attestation.Dal_dependent_signing.aggregate_pk
+                      ~subgroup_check:false
+                        (* We disable subgroup check (for better
+                           performances) because the context only
+                           contains valid consensus and companion
+                           keys. *)
+                      ~consensus_pk:consensus_bls_pk
+                      ~companion_pk
+                      dal_attestation
+                  in
+                  match dal_dependent_bls_pk_opt with
+                  | None ->
+                      tzfail
+                        Validate_errors.Consensus.Public_key_aggregation_failure
+                  | Some dal_dependent_bls_pk ->
+                      return
+                        (Signature.Bls dal_dependent_bls_pk
+                          : Signature.Public_key.t)))
+          | _ ->
+              (* When the feature flag is not set or the consensus key
+                 is non-BLS, we use the old behavior: the signed
+                 content (which includes the dal_content if any) is
+                 signed by the consensus key alone.
+
+                 When the dal_content is None (even with enabled
+                 feature flag and BLS consensus key), it is
+                 represented by [dal_dependent_pk =
+                 consensus_pk]. Notably, this allows a BLS consensus
+                 key without any associated companion key to still
+                 issue an attestation without DAL. *)
+              return consensus_key.consensus_pk
+        in
+        Operation.check_signature vi.ctxt dal_dependent_pk vi.chain_id operation
       else ok_unit
     in
     return voting_power
diff --git a/src/proto_alpha/lib_protocol/validate_errors.ml b/src/proto_alpha/lib_protocol/validate_errors.ml
index e01f026e71c4effb67c5b7995418d7f9f8e2b867..64555a25cd91c50ed1334f869f31dfd060568874 100644
--- a/src/proto_alpha/lib_protocol/validate_errors.ml
+++ b/src/proto_alpha/lib_protocol/validate_errors.ml
@@ -129,6 +129,7 @@ module Consensus = struct
         conflict : operation_conflict;
       }
     | Consensus_operation_not_allowed
+    | Missing_companion_key_for_bls_dal of Consensus_key.t
     | Aggregate_disabled
     | Aggregate_in_mempool
     | Aggregate_not_implemented
@@ -362,6 +363,16 @@ module Consensus = struct
       Data_encoding.empty
       (function Consensus_operation_not_allowed -> Some () | _ -> None)
       (fun () -> Consensus_operation_not_allowed) ;
+    register_error_kind
+      `Permanent
+      ~id:"validate.missing_companion_key_for_bls_dal"
+      ~title:"Missing companion key for DAL attestation with BLS"
+      ~description:
+        "The consensus key is a BLS key but is missing a companion key, so it \
+         cannot issue a DAL attestation"
+      Data_encoding.(obj1 (req "consensus_key" Consensus_key.encoding))
+      (function Missing_companion_key_for_bls_dal x -> Some x | _ -> None)
+      (fun x -> Missing_companion_key_for_bls_dal x) ;
     register_error_kind
       `Permanent
       ~id:"validate.aggregate_operation_not_allowed_in_mempool"
diff --git a/src/proto_alpha/lib_protocol/validate_errors.mli b/src/proto_alpha/lib_protocol/validate_errors.mli
index b95ca58bf12f658face616373b135ea634a00d31..f3d24a8d0f89a2c479a9d7af9b27a4cdff24f478 100644
--- a/src/proto_alpha/lib_protocol/validate_errors.mli
+++ b/src/proto_alpha/lib_protocol/validate_errors.mli
@@ -82,6 +82,7 @@ module Consensus : sig
         kind : consensus_operation_kind;
         conflict : operation_conflict;
       }
+    | Missing_companion_key_for_bls_dal of Consensus_key.t
     | Aggregate_disabled
     | Aggregate_in_mempool
     | Aggregate_not_implemented