diff --git a/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml b/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml
index 6b38c0f94a26653f9156d4b4ce30402e7a0cb960..6b01041224a57492813956dcfc8e12b78a48a86e 100644
--- a/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml
+++ b/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml
@@ -1622,7 +1622,11 @@ let commands_rw () =
         in
         match r with
         | Ok _ -> return_unit
-        | Error [Environment.Ecoproto_error Delegate_storage.Active_delegate] ->
+        | Error
+            [
+              Environment.Ecoproto_error
+                Delegate_storage.Contract.Active_delegate;
+            ] ->
             let*! () = cctxt#message "Delegate already activated." in
             return_unit
         | Error el -> Lwt.return_error el);
diff --git a/src/proto_alpha/lib_protocol/alpha_context.ml b/src/proto_alpha/lib_protocol/alpha_context.ml
index 0d730ba4372a6bd28cc61772258090c027aa20f3..63ee7e4e2037ac316679932e66d21bd9900fbdd2 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.ml
+++ b/src/proto_alpha/lib_protocol/alpha_context.ml
@@ -306,6 +306,12 @@ module Contract = struct
 
   let get_manager_key = Contract_manager_storage.get_manager_key
 
+  module Delegate = struct
+    let find = Contract_delegate_storage.find
+
+    include Delegate_storage.Contract
+  end
+
   module Internal_for_tests = struct
     include Contract_repr
     include Contract_storage
@@ -480,11 +486,9 @@ module Delegate = struct
 
   let prepare_stake_distribution = Stake_storage.prepare_stake_distribution
 
-  let registered = Contract_delegate_storage.registered
-
-  let find = Contract_delegate_storage.find
-
   let delegated_contracts = Contract_delegate_storage.delegated_contracts
+
+  let deactivated = Delegate_activation_storage.is_inactive
 end
 
 module Stake_distribution = struct
diff --git a/src/proto_alpha/lib_protocol/alpha_context.mli b/src/proto_alpha/lib_protocol/alpha_context.mli
index c430caa37d61aa669002a98a54b8272ebbac8019..fd1de02d68aa4a8dbb3405ece18d93cfcb64b228 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.mli
+++ b/src/proto_alpha/lib_protocol/alpha_context.mli
@@ -1350,9 +1350,6 @@ module Seed : sig
 
   val compute_randao : context -> context tzresult Lwt.t
 
-  val cycle_end :
-    context -> Cycle.t -> (context * Nonce.unrevealed list) tzresult Lwt.t
-
   (* RPC *)
   type seed_computation_status =
     | Nonce_revelation_stage
@@ -1670,15 +1667,13 @@ end
 (** This module re-exports definitions from {!Contract_repr} and
     {!Contract_storage}. *)
 module Contract : sig
-  type t =
-    | Implicit of Signature.Public_key_hash.t
-    | Originated of Contract_hash.t
+  type t = Implicit of public_key_hash | Originated of Contract_hash.t
 
   type error += Non_existing_contract of t
 
   include BASIC_DATA with type t := t
 
-  val implicit_encoding : Signature.public_key_hash Data_encoding.t
+  val implicit_encoding : public_key_hash Data_encoding.t
 
   val originated_encoding : Contract_hash.t Data_encoding.t
 
@@ -1804,6 +1799,18 @@ module Contract : sig
     script:Script.t * Lazy_storage.diffs option ->
     context tzresult Lwt.t
 
+  (** Functions for handling the delegate of a contract.*)
+  module Delegate : sig
+    (** See {!Contract_delegate_storage.find}. *)
+    val find : context -> t -> public_key_hash option tzresult Lwt.t
+
+    (** See {!Delegate_storage.Contract.init}. *)
+    val init : context -> t -> public_key_hash -> context tzresult Lwt.t
+
+    (** See {!Delegate_storage.Contract.set}. *)
+    val set : context -> t -> public_key_hash option -> context tzresult Lwt.t
+  end
+
   (** This module discloses definitions that are only useful for tests and must
       not be used otherwise. *)
   module Internal_for_tests : sig
@@ -1871,7 +1878,7 @@ end
 (** This module re-exports definitions from {!Tx_rollup_withdraw_repr}. *)
 module Tx_rollup_withdraw : sig
   type order = {
-    claimer : Signature.Public_key_hash.t;
+    claimer : public_key_hash;
     ticket_hash : Ticket_hash.t;
     amount : Tx_rollup_l2_qty.t;
   }
@@ -2005,7 +2012,7 @@ module Tx_rollup_reveal : sig
     ty : Script.lazy_expr;
     ticketer : Contract.t;
     amount : Tx_rollup_l2_qty.t;
-    claimer : Signature.Public_key_hash.t;
+    claimer : public_key_hash;
   }
 
   val encoding : t Data_encoding.t
@@ -2160,7 +2167,7 @@ module Tx_rollup_commitment : sig
     type nonrec t = {
       commitment : Compact.t;
       commitment_hash : Tx_rollup_commitment_hash.t;
-      committer : Signature.Public_key_hash.t;
+      committer : public_key_hash;
       submitted_at : Raw_level.t;
       finalized_at : Raw_level.t option;
     }
@@ -2191,10 +2198,9 @@ module Tx_rollup_commitment : sig
     context ->
     Tx_rollup.t ->
     Tx_rollup_state.t ->
-    Signature.public_key_hash ->
+    public_key_hash ->
     Full.t ->
-    (context * Tx_rollup_state.t * Signature.public_key_hash option) tzresult
-    Lwt.t
+    (context * Tx_rollup_state.t * public_key_hash option) tzresult Lwt.t
 
   val find :
     context ->
@@ -2230,16 +2236,10 @@ module Tx_rollup_commitment : sig
     (context * Submitted_commitment.t) tzresult Lwt.t
 
   val pending_bonded_commitments :
-    context ->
-    Tx_rollup.t ->
-    Signature.public_key_hash ->
-    (context * int) tzresult Lwt.t
+    context -> Tx_rollup.t -> public_key_hash -> (context * int) tzresult Lwt.t
 
   val has_bond :
-    context ->
-    Tx_rollup.t ->
-    Signature.public_key_hash ->
-    (context * bool) tzresult Lwt.t
+    context -> Tx_rollup.t -> public_key_hash -> (context * bool) tzresult Lwt.t
 
   val finalize_commitment :
     context ->
@@ -2254,16 +2254,10 @@ module Tx_rollup_commitment : sig
     (context * Tx_rollup_state.t * Tx_rollup_level.t) tzresult Lwt.t
 
   val remove_bond :
-    context ->
-    Tx_rollup.t ->
-    Signature.public_key_hash ->
-    context tzresult Lwt.t
+    context -> Tx_rollup.t -> public_key_hash -> context tzresult Lwt.t
 
   val slash_bond :
-    context ->
-    Tx_rollup.t ->
-    Signature.public_key_hash ->
-    (context * bool) tzresult Lwt.t
+    context -> Tx_rollup.t -> public_key_hash -> (context * bool) tzresult Lwt.t
 
   val reject_commitment :
     context ->
@@ -2311,8 +2305,8 @@ module Tx_rollup_errors : sig
       }
     | Level_already_has_commitment of Tx_rollup_level.t
     | Wrong_inbox_hash
-    | Bond_does_not_exist of Signature.public_key_hash
-    | Bond_in_use of Signature.public_key_hash
+    | Bond_does_not_exist of public_key_hash
+    | Bond_in_use of public_key_hash
     | No_uncommitted_inbox
     | No_commitment_to_finalize
     | No_commitment_to_remove
@@ -2481,7 +2475,7 @@ module Receipt : sig
     | Baking_bonuses
     | Storage_fees
     | Double_signing_punishments
-    | Lost_endorsing_rewards of Signature.Public_key_hash.t * bool * bool
+    | Lost_endorsing_rewards of public_key_hash * bool * bool
     | Liquidity_baking_subsidies
     | Burned
     | Commitments of Blinded_public_key_hash.t
@@ -2518,23 +2512,11 @@ end
    {!Delegate_missed_endorsements_storage},
    {!Delegate_slashed_deposits_storage}, {!Delegate_cycles}. *)
 module Delegate : sig
-  val init :
-    context ->
-    Contract.t ->
-    Signature.Public_key_hash.t ->
-    context tzresult Lwt.t
-
-  (** See {!Contract_delegate_storage.find}. *)
-  val find : context -> Contract.t -> public_key_hash option tzresult Lwt.t
-
-  val set :
-    context -> Contract.t -> public_key_hash option -> context tzresult Lwt.t
-
   val frozen_deposits_limit :
-    context -> Signature.Public_key_hash.t -> Tez.t option tzresult Lwt.t
+    context -> public_key_hash -> Tez.t option tzresult Lwt.t
 
   val set_frozen_deposits_limit :
-    context -> Signature.Public_key_hash.t -> Tez.t option -> context Lwt.t
+    context -> public_key_hash -> Tez.t option -> context Lwt.t
 
   val fold :
     context ->
@@ -2560,10 +2542,7 @@ module Delegate : sig
   val cycle_end :
     context ->
     Cycle.t ->
-    Nonce.unrevealed list ->
-    (context * Receipt.balance_updates * Signature.Public_key_hash.t list)
-    tzresult
-    Lwt.t
+    (context * Receipt.balance_updates * public_key_hash list) tzresult Lwt.t
 
   val already_slashed_for_double_endorsing :
     context -> public_key_hash -> Level.t -> bool tzresult Lwt.t
@@ -2589,15 +2568,15 @@ module Delegate : sig
 
   val record_baking_activity_and_pay_rewards_and_fees :
     context ->
-    payload_producer:Signature.Public_key_hash.t ->
-    block_producer:Signature.Public_key_hash.t ->
+    payload_producer:public_key_hash ->
+    block_producer:public_key_hash ->
     baking_reward:Tez.t ->
     reward_bonus:Tez.t option ->
     (context * Receipt.balance_updates) tzresult Lwt.t
 
   val record_endorsing_participation :
     context ->
-    delegate:Signature.Public_key_hash.t ->
+    delegate:public_key_hash ->
     participation:level_participation ->
     endorsing_power:int ->
     context tzresult Lwt.t
@@ -2606,25 +2585,20 @@ module Delegate : sig
 
   val frozen_deposits : context -> public_key_hash -> deposits tzresult Lwt.t
 
-  val staking_balance :
-    context -> Signature.Public_key_hash.t -> Tez.t tzresult Lwt.t
+  val staking_balance : context -> public_key_hash -> Tez.t tzresult Lwt.t
 
   (** See {!Contract_delegate_storage.delegated_contracts}. *)
-  val delegated_contracts :
-    context -> Signature.Public_key_hash.t -> Contract.t list Lwt.t
+  val delegated_contracts : context -> public_key_hash -> Contract.t list Lwt.t
 
-  val delegated_balance :
-    context -> Signature.Public_key_hash.t -> Tez.t tzresult Lwt.t
+  val delegated_balance : context -> public_key_hash -> Tez.t tzresult Lwt.t
 
-  (** See {!Contract_delegate_storage.registered}. *)
-  val registered : context -> Signature.Public_key_hash.t -> bool tzresult Lwt.t
+  val registered : context -> public_key_hash -> bool Lwt.t
 
-  val deactivated :
-    context -> Signature.Public_key_hash.t -> bool tzresult Lwt.t
+  val deactivated : context -> public_key_hash -> bool tzresult Lwt.t
 
   (** See {!Delegate_activation_storage.last_cycle_before_deactivation}. *)
   val last_cycle_before_deactivation :
-    context -> Signature.Public_key_hash.t -> Cycle.t tzresult Lwt.t
+    context -> public_key_hash -> Cycle.t tzresult Lwt.t
 
   val pubkey : context -> public_key_hash -> public_key tzresult Lwt.t
 
@@ -2705,8 +2679,7 @@ module Vote : sig
 
   val clear_proposals : context -> context Lwt.t
 
-  val listings_encoding :
-    (Signature.Public_key_hash.t * int64) list Data_encoding.t
+  val listings_encoding : (public_key_hash * int64) list Data_encoding.t
 
   val update_listings : context -> context tzresult Lwt.t
 
@@ -2732,13 +2705,12 @@ module Vote : sig
   val delegate_info_encoding : delegate_info Data_encoding.t
 
   val get_delegate_info :
-    context -> Signature.Public_key_hash.t -> delegate_info tzresult Lwt.t
+    context -> public_key_hash -> delegate_info tzresult Lwt.t
 
-  val get_voting_power_free :
-    context -> Signature.Public_key_hash.t -> int64 tzresult Lwt.t
+  val get_voting_power_free : context -> public_key_hash -> int64 tzresult Lwt.t
 
   val get_voting_power :
-    context -> Signature.Public_key_hash.t -> (context * int64) tzresult Lwt.t
+    context -> public_key_hash -> (context * int64) tzresult Lwt.t
 
   val get_total_voting_power_free : context -> int64 tzresult Lwt.t
 
@@ -2827,7 +2799,7 @@ module Dal : sig
 
     val expected_size_in_bits : max_index:Slot_index.t -> int
 
-    val shards : context -> endorser:Signature.Public_key_hash.t -> int list
+    val shards : context -> endorser:public_key_hash -> int list
 
     val record_available_shards : context -> t -> int list -> context
   end
@@ -2914,8 +2886,7 @@ module Sc_rollup : sig
 
   val in_memory_size : t -> Cache_memory_helpers.sint
 
-  module Staker :
-    S.SIGNATURE_PUBLIC_KEY_HASH with type t = Signature.Public_key_hash.t
+  module Staker : S.SIGNATURE_PUBLIC_KEY_HASH with type t = public_key_hash
 
   module State_hash : sig
     include S.HASH
@@ -2937,7 +2908,7 @@ module Sc_rollup : sig
       type internal_inbox_message = {
         payload : Script.expr;
         sender : Contract_hash.t;
-        source : Signature.public_key_hash;
+        source : public_key_hash;
       }
 
       type t = Internal of internal_inbox_message | External of string
@@ -3111,7 +3082,7 @@ module Sc_rollup : sig
       rollup ->
       payload:Script.expr ->
       sender:Contract_hash.t ->
-      source:Signature.public_key_hash ->
+      source:public_key_hash ->
       (t * Z.t * context) tzresult Lwt.t
 
     val inbox : context -> rollup -> (t * context) tzresult Lwt.t
@@ -3656,8 +3627,8 @@ module Sc_rollup : sig
     val start_game :
       context ->
       t ->
-      player:Signature.public_key_hash ->
-      opponent:Signature.public_key_hash ->
+      player:public_key_hash ->
+      opponent:public_key_hash ->
       context tzresult Lwt.t
 
     val game_move :
@@ -3752,7 +3723,7 @@ module Block_header : sig
       Liquidity_baking_repr.liquidity_baking_toggle_vote;
   }
 
-  type protocol_data = {contents : contents; signature : Signature.t}
+  type protocol_data = {contents : contents; signature : signature}
 
   type t = {shell : Block_header.shell_header; protocol_data : protocol_data}
 
@@ -3809,8 +3780,7 @@ module Block_header : sig
     predecessor_round:Round.t ->
     unit tzresult
 
-  val check_signature :
-    t -> Chain_id.t -> Signature.Public_key.t -> unit tzresult
+  val check_signature : t -> Chain_id.t -> public_key -> unit tzresult
 
   val begin_validate_block_header :
     block_header:t ->
@@ -3819,7 +3789,7 @@ module Block_header : sig
     predecessor_round:Round.t ->
     fitness:Fitness.t ->
     timestamp:Time.t ->
-    delegate_pk:Signature.public_key ->
+    delegate_pk:public_key ->
     round_durations:Round.round_durations ->
     proof_of_work_threshold:int64 ->
     expected_commitment:bool ->
@@ -4006,7 +3976,7 @@ type 'kind operation = {
 
 and 'kind protocol_data = {
   contents : 'kind contents_list;
-  signature : Signature.t option;
+  signature : signature option;
 }
 
 and _ contents_list =
@@ -4019,7 +3989,7 @@ and _ contents =
   | Preendorsement : consensus_content -> Kind.preendorsement contents
   | Endorsement : consensus_content -> Kind.endorsement contents
   | Dal_slot_availability :
-      Signature.Public_key_hash.t * Dal.Endorsement.t
+      public_key_hash * Dal.Endorsement.t
       -> Kind.dal_slot_availability contents
   | Seed_nonce_revelation : {
       level : Raw_level.t;
@@ -4051,13 +4021,13 @@ and _ contents =
     }
       -> Kind.activate_account contents
   | Proposals : {
-      source : Signature.Public_key_hash.t;
+      source : public_key_hash;
       period : int32;
       proposals : Protocol_hash.t list;
     }
       -> Kind.proposals contents
   | Ballot : {
-      source : Signature.Public_key_hash.t;
+      source : public_key_hash;
       period : int32;
       proposal : Protocol_hash.t;
       ballot : Vote.ballot;
@@ -4065,7 +4035,7 @@ and _ contents =
       -> Kind.ballot contents
   | Failing_noop : string -> Kind.failing_noop contents
   | Manager_operation : {
-      source : Signature.Public_key_hash.t;
+      source : public_key_hash;
       fee : Tez.tez;
       counter : counter;
       operation : 'kind manager_operation;
@@ -4075,7 +4045,7 @@ and _ contents =
       -> 'kind Kind.manager contents
 
 and _ manager_operation =
-  | Reveal : Signature.Public_key.t -> Kind.reveal manager_operation
+  | Reveal : public_key -> Kind.reveal manager_operation
   | Transaction : {
       amount : Tez.tez;
       parameters : Script.lazy_expr;
@@ -4084,14 +4054,12 @@ and _ manager_operation =
     }
       -> Kind.transaction manager_operation
   | Origination : {
-      delegate : Signature.Public_key_hash.t option;
+      delegate : public_key_hash option;
       script : Script.t;
       credit : Tez.tez;
     }
       -> Kind.origination manager_operation
-  | Delegation :
-      Signature.Public_key_hash.t option
-      -> Kind.delegation manager_operation
+  | Delegation : public_key_hash option -> Kind.delegation manager_operation
   | Register_global_constant : {
       value : Script.lazy_expr;
     }
@@ -4704,8 +4672,8 @@ module Token : sig
   type container =
     [ `Contract of Contract.t
     | `Collected_commitments of Blinded_public_key_hash.t
-    | `Delegate_balance of Signature.Public_key_hash.t
-    | `Frozen_deposits of Signature.Public_key_hash.t
+    | `Delegate_balance of public_key_hash
+    | `Frozen_deposits of public_key_hash
     | `Block_fees
     | `Frozen_bonds of Contract.t * Bond_id.t ]
 
@@ -4727,7 +4695,7 @@ module Token : sig
   type sink =
     [ `Storage_fees
     | `Double_signing_punishments
-    | `Lost_endorsing_rewards of Signature.Public_key_hash.t * bool * bool
+    | `Lost_endorsing_rewards of public_key_hash * bool * bool
     | `Burned
     | `Tx_rollup_rejection_punishments
     | `Sc_rollup_refutation_punishments
diff --git a/src/proto_alpha/lib_protocol/apply.ml b/src/proto_alpha/lib_protocol/apply.ml
index f82c5a2095f8d5552c686c8566990da7cdda68c2..43cbd7fea9c25744aec038862b42b08d35c61918 100644
--- a/src/proto_alpha/lib_protocol/apply.ml
+++ b/src/proto_alpha/lib_protocol/apply.ml
@@ -273,7 +273,7 @@ let update_script_storage_and_ticket_balances ctxt ~self storage
   Ticket_accounting.update_ticket_balances ctxt ~self ~ticket_diffs operations
 
 let apply_delegation ~ctxt ~source ~delegate ~before_operation =
-  Delegate.set ctxt source delegate >|=? fun ctxt ->
+  Contract.Delegate.set ctxt source delegate >|=? fun ctxt ->
   (ctxt, Gas.consumed ~since:before_operation ~until:ctxt, [])
 
 type 'loc execution_arg =
@@ -522,7 +522,7 @@ let apply_origination ~ctxt ~storage_type ~storage ~unparsed_code
   let contract = Contract.Originated contract_hash in
   (match delegate with
   | None -> return ctxt
-  | Some delegate -> Delegate.init ctxt contract delegate)
+  | Some delegate -> Contract.Delegate.init ctxt contract delegate)
   >>=? fun ctxt ->
   Token.transfer ctxt (`Contract source) (`Contract contract) credit
   >>=? fun (ctxt, balance_updates) ->
@@ -1011,7 +1011,7 @@ let apply_manager_operation :
             Tez.(limit > max_limit)
             (Set_deposits_limit_too_high {limit; max_limit}))
       >>?= fun () ->
-      Delegate.registered ctxt source >>=? fun is_registered ->
+      Delegate.registered ctxt source >>= fun is_registered ->
       error_unless
         is_registered
         (Set_deposits_limit_on_unregistered_delegate source)
@@ -2175,8 +2175,7 @@ let may_start_new_cycle ctxt =
   match Level.dawn_of_a_new_cycle ctxt with
   | None -> return (ctxt, [], [])
   | Some last_cycle ->
-      Seed.cycle_end ctxt last_cycle >>=? fun (ctxt, unrevealed) ->
-      Delegate.cycle_end ctxt last_cycle unrevealed
+      Delegate.cycle_end ctxt last_cycle
       >>=? fun (ctxt, balance_updates, deactivated) ->
       Bootstrap.cycle_end ctxt last_cycle >|=? fun ctxt ->
       (ctxt, balance_updates, deactivated)
diff --git a/src/proto_alpha/lib_protocol/bootstrap_storage.ml b/src/proto_alpha/lib_protocol/bootstrap_storage.ml
index b9abaec549892bbc65886880f281d64cd5368800..592bdebbec46a3168cd6f2d1e6bf2f66c0ca07e7 100644
--- a/src/proto_alpha/lib_protocol/bootstrap_storage.ml
+++ b/src/proto_alpha/lib_protocol/bootstrap_storage.ml
@@ -59,7 +59,7 @@ let init_account (ctxt, balance_updates)
         public_key_hash
         public_key
       >>=? fun ctxt ->
-      Delegate_storage.set
+      Delegate_storage.Contract.set
         ctxt
         contract
         (Some (Option.value ~default:public_key_hash delegate_to))
@@ -84,7 +84,7 @@ let init_contract ~typecheck (ctxt, balance_updates)
   let contract = Contract_repr.Originated contract_hash in
   (match delegate with
   | None -> return ctxt
-  | Some delegate -> Delegate_storage.init ctxt contract delegate)
+  | Some delegate -> Delegate_storage.Contract.init ctxt contract delegate)
   >>=? fun ctxt ->
   let origin = Receipt_repr.Protocol_migration in
   Token.transfer ~origin ctxt `Bootstrap (`Contract contract) amount
diff --git a/src/proto_alpha/lib_protocol/contract_delegate_storage.ml b/src/proto_alpha/lib_protocol/contract_delegate_storage.ml
index 8dbb1063250d137bb618ecbbea219224ce703804..75efd48243daa84662d3c0079af54998d5758763 100644
--- a/src/proto_alpha/lib_protocol/contract_delegate_storage.ml
+++ b/src/proto_alpha/lib_protocol/contract_delegate_storage.ml
@@ -25,14 +25,6 @@
 
 let find = Storage.Contract.Delegate.find
 
-(* A delegate is registered if its "implicit account" delegates to itself. *)
-let registered c delegate =
-  Storage.Contract.Delegate.find c (Contract_repr.Implicit delegate)
-  >|=? function
-  | Some current_delegate ->
-      Signature.Public_key_hash.equal delegate current_delegate
-  | None -> false
-
 let init ctxt contract delegate =
   Storage.Contract.Delegate.init ctxt contract delegate >>=? fun ctxt ->
   let delegate_contract = Contract_repr.Implicit delegate in
diff --git a/src/proto_alpha/lib_protocol/contract_delegate_storage.mli b/src/proto_alpha/lib_protocol/contract_delegate_storage.mli
index ac62d6ecd423259ca153c08f7596a7c9f697c14f..189a03df8fdf1ea3d5f861ba8b749297952dac6e 100644
--- a/src/proto_alpha/lib_protocol/contract_delegate_storage.mli
+++ b/src/proto_alpha/lib_protocol/contract_delegate_storage.mli
@@ -34,15 +34,9 @@ val find :
   Contract_repr.t ->
   Signature.Public_key_hash.t option tzresult Lwt.t
 
-(** [registered ctxt delegate] returns true iff delegate is an implicit contract
-    that delegates to itself. *)
-val registered :
-  Raw_context.t -> Signature.Public_key_hash.t -> bool tzresult Lwt.t
-
 (** [init ctxt contract delegate] sets the [delegate] associated to [contract].
 
-    This function is undefined if [contract] is not allocated, or if [contract]
-    has already a delegate. *)
+    This function assumes that [contract] does not have a delegate already. *)
 val init :
   Raw_context.t ->
   Contract_repr.t ->
@@ -54,20 +48,19 @@ val init :
     This function does not affect the value of the expression
     [find ctxt contract].
 
-    This function is undefined if [contract] is not allocated. *)
+    This function assumes that [contract] is allocated. *)
 val unlink : Raw_context.t -> Contract_repr.t -> Raw_context.t tzresult Lwt.t
 
 (** [delete ctxt contract] behaves as [unlink ctxt contract], but in addition
     removes the association of the [contract] to its current delegate, leaving
     the former without delegate.
 
-    This function is undefined if [contract] is not allocated. *)
+    This function assumes that [contract] is allocated. *)
 val delete : Raw_context.t -> Contract_repr.t -> Raw_context.t tzresult Lwt.t
 
 (** [set ctxt contract delegate] updates the [delegate] associated to [contract].
 
-    This function is undefined if [contract] is not allocated, or if [contract]
-    does not have a delegate. *)
+    This function assumes that [contract] is allocated and has a delegate. *)
 val set :
   Raw_context.t ->
   Contract_repr.t ->
diff --git a/src/proto_alpha/lib_protocol/contract_services.ml b/src/proto_alpha/lib_protocol/contract_services.ml
index 89ea4ce0f4fe1ab65cb8ecbead5ca83a95ce3028..e7f7bd5766f0cf4184100b19038bb0320ad11e93 100644
--- a/src/proto_alpha/lib_protocol/contract_services.ml
+++ b/src/proto_alpha/lib_protocol/contract_services.ml
@@ -401,7 +401,7 @@ let register () =
           | false -> return_some None
           | true ->
               Contract.get_manager_key ctxt mgr >|=? fun key -> Some (Some key))) ;
-  register_opt_field ~chunked:false S.delegate Delegate.find ;
+  register_opt_field ~chunked:false S.delegate Contract.Delegate.find ;
   opt_register1 ~chunked:false S.counter (fun ctxt contract () () ->
       match contract with
       | Originated _ -> return_none
@@ -555,7 +555,7 @@ let register () =
     S.info
     (fun ctxt contract {normalize_types} ->
       Contract.get_balance ctxt contract >>=? fun balance ->
-      Delegate.find ctxt contract >>=? fun delegate ->
+      Contract.Delegate.find ctxt contract >>=? fun delegate ->
       match contract with
       | Implicit manager ->
           Contract.get_counter ctxt manager >|=? fun counter ->
diff --git a/src/proto_alpha/lib_protocol/contract_storage.mli b/src/proto_alpha/lib_protocol/contract_storage.mli
index 8b6890c863c6cadc5467ca72fb148f4531b4a5b9..c08e7b45fb5797bfdf19c545da4008764bdec865 100644
--- a/src/proto_alpha/lib_protocol/contract_storage.mli
+++ b/src/proto_alpha/lib_protocol/contract_storage.mli
@@ -46,7 +46,7 @@ type error +=
       Signature.Public_key_hash.t
 
 (** [allocated ctxt contract] returns [true] if and only if the
-   contract is stored in [Storage.Contract.Balance]. *)
+   contract is stored in {!Storage.Contract.Spendable_balance}. *)
 val allocated : Raw_context.t -> Contract_repr.t -> bool Lwt.t
 
 (** [exists ctxt contract] returns [true] if and only if either the
diff --git a/src/proto_alpha/lib_protocol/delegate_activation_storage.mli b/src/proto_alpha/lib_protocol/delegate_activation_storage.mli
index 911bf6c30b08035023d5ee78d24d7de876b0939d..390d37cbef2f0ca55d48ca6f063f1fe5ea3e5c7a 100644
--- a/src/proto_alpha/lib_protocol/delegate_activation_storage.mli
+++ b/src/proto_alpha/lib_protocol/delegate_activation_storage.mli
@@ -40,7 +40,7 @@ val last_cycle_before_deactivation :
   Raw_context.t -> Signature.Public_key_hash.t -> Cycle_repr.t tzresult Lwt.t
 
 (** [set_inactive context delegate] adds [delegate] to the set of inactive
- * contracts. *)
+    contracts. *)
 val set_inactive :
   Raw_context.t -> Signature.Public_key_hash.t -> Raw_context.t Lwt.t
 
diff --git a/src/proto_alpha/lib_protocol/delegate_cycles.ml b/src/proto_alpha/lib_protocol/delegate_cycles.ml
index 0a2dac5e6c7823e0cda08a4dac964bd385fcd2f0..27c1fa572ed7d4b6b5d99576309a64ad5eaf47e0 100644
--- a/src/proto_alpha/lib_protocol/delegate_cycles.ml
+++ b/src/proto_alpha/lib_protocol/delegate_cycles.ml
@@ -41,8 +41,8 @@ let update_activity ctxt last_cycle =
             delegate
           >>=? fun cycle ->
           if Cycle_repr.(cycle <= last_cycle) then
-            Delegate_storage.set_inactive ctxt delegate >|=? fun ctxt ->
-            (ctxt, delegate :: deactivated)
+            Stake_storage.set_inactive ctxt delegate >>= fun ctxt ->
+            return (ctxt, delegate :: deactivated)
           else return (ctxt, deactivated))
       >|=? fun (ctxt, deactivated) -> (ctxt, deactivated)
 
@@ -247,7 +247,8 @@ let distribute_endorsing_rewards ctxt last_cycle unrevealed_nonces =
     (ctxt, [])
     delegates
 
-let cycle_end ctxt last_cycle unrevealed_nonces =
+let cycle_end ctxt last_cycle =
+  Seed_storage.cycle_end ctxt last_cycle >>=? fun (ctxt, unrevealed_nonces) ->
   let new_cycle = Cycle_repr.add last_cycle 1 in
   Delegate_sampler.select_new_distribution_at_cycle_end ctxt ~new_cycle
   >>=? fun ctxt ->
diff --git a/src/proto_alpha/lib_protocol/delegate_cycles.mli b/src/proto_alpha/lib_protocol/delegate_cycles.mli
index 7fb56220567c59efae60e2592c7368f4687808d5..1b7f8a87bad6cc85ca7982ef207c33d5e6fb0ae0 100644
--- a/src/proto_alpha/lib_protocol/delegate_cycles.mli
+++ b/src/proto_alpha/lib_protocol/delegate_cycles.mli
@@ -34,7 +34,6 @@
 val cycle_end :
   Raw_context.t ->
   Cycle_repr.t ->
-  Storage.Seed.unrevealed_nonce list ->
   (Raw_context.t
   * Receipt_repr.balance_updates
   * Signature.Public_key_hash.t list)
diff --git a/src/proto_alpha/lib_protocol/delegate_missed_endorsements_storage.ml b/src/proto_alpha/lib_protocol/delegate_missed_endorsements_storage.ml
index 2d1ef3030d6bb43880a7a7a89ad25644ac687bcd..48d3be9240d52a292ec1990e807bd0d9a2a1928f 100644
--- a/src/proto_alpha/lib_protocol/delegate_missed_endorsements_storage.ml
+++ b/src/proto_alpha/lib_protocol/delegate_missed_endorsements_storage.ml
@@ -50,7 +50,7 @@ type level_participation = Participated | Didn't_participate
 let record_endorsing_participation ctxt ~delegate ~participation
     ~endorsing_power =
   match participation with
-  | Participated -> Delegate_storage.set_active ctxt delegate
+  | Participated -> Stake_storage.set_active ctxt delegate
   | Didn't_participate -> (
       let contract = Contract_repr.Implicit delegate in
       Storage.Contract.Missed_endorsements.find ctxt contract >>=? function
@@ -97,9 +97,9 @@ let record_endorsing_participation ctxt ~delegate ~participation
 
 let record_baking_activity_and_pay_rewards_and_fees ctxt ~payload_producer
     ~block_producer ~baking_reward ~reward_bonus =
-  Delegate_storage.set_active ctxt payload_producer >>=? fun ctxt ->
+  Stake_storage.set_active ctxt payload_producer >>=? fun ctxt ->
   (if not (Signature.Public_key_hash.equal payload_producer block_producer) then
-   Delegate_storage.set_active ctxt block_producer
+   Stake_storage.set_active ctxt block_producer
   else return ctxt)
   >>=? fun ctxt ->
   let pay_payload_producer ctxt delegate =
diff --git a/src/proto_alpha/lib_protocol/delegate_services.ml b/src/proto_alpha/lib_protocol/delegate_services.ml
index e8426d3dd35b8cab5563732f32e2b693ed5934d8..5efd3ecbe425df52ee6d5afeabc2a87dbe0aa507 100644
--- a/src/proto_alpha/lib_protocol/delegate_services.ml
+++ b/src/proto_alpha/lib_protocol/delegate_services.ml
@@ -356,7 +356,7 @@ module S = struct
 end
 
 let check_delegate_registered ctxt pkh =
-  Delegate.registered ctxt pkh >>=? function
+  Delegate.registered ctxt pkh >>= function
   | true -> return_unit
   | false -> fail (Not_registered pkh)
 
diff --git a/src/proto_alpha/lib_protocol/delegate_storage.ml b/src/proto_alpha/lib_protocol/delegate_storage.ml
index 3399246a130c97d92ee1f087b9469cd42d3fb269..28e96c3f2ff1a888a84eb251005c4f946425c4fa 100644
--- a/src/proto_alpha/lib_protocol/delegate_storage.ml
+++ b/src/proto_alpha/lib_protocol/delegate_storage.ml
@@ -26,64 +26,9 @@
 (*****************************************************************************)
 
 type error +=
-  | (* `Permanent *) No_deletion of Signature.Public_key_hash.t
-  | (* `Temporary *) Active_delegate
-  | (* `Temporary *) Current_delegate
-  | (* `Permanent *) Empty_delegate_account of Signature.Public_key_hash.t
   | (* `Permanent *) Unregistered_delegate of Signature.Public_key_hash.t
 
 let () =
-  register_error_kind
-    `Permanent
-    ~id:"delegate.no_deletion"
-    ~title:"Forbidden delegate deletion"
-    ~description:"Tried to unregister a delegate"
-    ~pp:(fun ppf delegate ->
-      Format.fprintf
-        ppf
-        "Delegate deletion is forbidden (%a)"
-        Signature.Public_key_hash.pp
-        delegate)
-    Data_encoding.(obj1 (req "delegate" Signature.Public_key_hash.encoding))
-    (function No_deletion c -> Some c | _ -> None)
-    (fun c -> No_deletion c) ;
-  register_error_kind
-    `Temporary
-    ~id:"delegate.already_active"
-    ~title:"Delegate already active"
-    ~description:"Useless delegate reactivation"
-    ~pp:(fun ppf () ->
-      Format.fprintf ppf "The delegate is still active, no need to refresh it")
-    Data_encoding.empty
-    (function Active_delegate -> Some () | _ -> None)
-    (fun () -> Active_delegate) ;
-  register_error_kind
-    `Temporary
-    ~id:"delegate.unchanged"
-    ~title:"Unchanged delegated"
-    ~description:"Contract already delegated to the given delegate"
-    ~pp:(fun ppf () ->
-      Format.fprintf
-        ppf
-        "The contract is already delegated to the same delegate")
-    Data_encoding.empty
-    (function Current_delegate -> Some () | _ -> None)
-    (fun () -> Current_delegate) ;
-  register_error_kind
-    `Permanent
-    ~id:"delegate.empty_delegate_account"
-    ~title:"Empty delegate account"
-    ~description:"Cannot register a delegate when its implicit account is empty"
-    ~pp:(fun ppf delegate ->
-      Format.fprintf
-        ppf
-        "Delegate registration is forbidden when the delegate\n\
-        \           implicit account is empty (%a)"
-        Signature.Public_key_hash.pp
-        delegate)
-    Data_encoding.(obj1 (req "delegate" Signature.Public_key_hash.encoding))
-    (function Empty_delegate_account c -> Some c | _ -> None)
-    (fun c -> Empty_delegate_account c) ;
   (* Unregistered delegate *)
   register_error_kind
     `Permanent
@@ -101,96 +46,166 @@ let () =
     (function Unregistered_delegate k -> Some k | _ -> None)
     (fun k -> Unregistered_delegate k)
 
-let set_inactive ctxt delegate =
-  Delegate_activation_storage.set_inactive ctxt delegate >>= fun ctxt ->
-  Stake_storage.deactivate_only_call_from_delegate_storage ctxt delegate >|= ok
-
-let set_active ctxt delegate =
-  Delegate_activation_storage.set_active ctxt delegate
-  >>=? fun (ctxt, inactive) ->
-  if not inactive then return ctxt
-  else Stake_storage.activate_only_call_from_delegate_storage ctxt delegate
-
-let deactivated = Delegate_activation_storage.is_inactive
-
-let init ctxt contract delegate =
-  Contract_manager_storage.is_manager_key_revealed ctxt delegate
-  >>=? fun known_delegate ->
-  error_unless known_delegate (Unregistered_delegate delegate) >>?= fun () ->
-  Contract_delegate_storage.registered ctxt delegate >>=? fun is_registered ->
-  error_unless is_registered (Unregistered_delegate delegate) >>?= fun () ->
-  Contract_delegate_storage.init ctxt contract delegate >>=? fun ctxt ->
-  Contract_storage.get_balance_and_frozen_bonds ctxt contract
-  >>=? fun balance_and_frozen_bonds ->
-  Stake_storage.add_stake ctxt delegate balance_and_frozen_bonds
-
-let set c contract delegate =
-  match delegate with
-  | None -> (
-      (* check if contract is a registered delegate *)
-      (match contract with
-      | Contract_repr.Implicit pkh ->
-          Contract_delegate_storage.registered c pkh >>=? fun is_registered ->
-          fail_when is_registered (No_deletion pkh)
-      | Originated _ -> return_unit)
-      >>=? fun () ->
-      Contract_delegate_storage.find c contract >>=? function
-      | None -> return c
-      | Some delegate ->
-          (* Removes the balance of the contract from the delegate *)
-          Contract_storage.get_balance_and_frozen_bonds c contract
-          >>=? fun balance_and_frozen_bonds ->
-          Stake_storage.remove_stake c delegate balance_and_frozen_bonds
-          >>=? fun c -> Contract_delegate_storage.delete c contract)
-  | Some delegate ->
-      Contract_manager_storage.is_manager_key_revealed c delegate
-      >>=? fun known_delegate ->
-      Contract_delegate_storage.registered c delegate
-      >>=? fun registered_delegate ->
-      let self_delegation =
-        match contract with
-        | Implicit pkh -> Signature.Public_key_hash.equal pkh delegate
-        | Originated _ -> false
+let registered = Storage.Delegates.mem
+
+module Contract = struct
+  let init ctxt contract delegate =
+    Contract_manager_storage.is_manager_key_revealed ctxt delegate
+    >>=? fun known_delegate ->
+    error_unless known_delegate (Unregistered_delegate delegate) >>?= fun () ->
+    registered ctxt delegate >>= fun is_registered ->
+    error_unless is_registered (Unregistered_delegate delegate) >>?= fun () ->
+    Contract_delegate_storage.init ctxt contract delegate >>=? fun ctxt ->
+    Contract_storage.get_balance_and_frozen_bonds ctxt contract
+    >>=? fun balance_and_frozen_bonds ->
+    Stake_storage.add_stake ctxt delegate balance_and_frozen_bonds
+
+  type error +=
+    | (* `Temporary *) Active_delegate
+    | (* `Permanent *) Empty_delegate_account of Signature.Public_key_hash.t
+
+  let () =
+    register_error_kind
+      `Temporary
+      ~id:"delegate.already_active"
+      ~title:"Delegate already active"
+      ~description:"Useless delegate reactivation"
+      ~pp:(fun ppf () ->
+        Format.fprintf ppf "The delegate is still active, no need to refresh it")
+      Data_encoding.empty
+      (function Active_delegate -> Some () | _ -> None)
+      (fun () -> Active_delegate) ;
+    register_error_kind
+      `Permanent
+      ~id:"delegate.empty_delegate_account"
+      ~title:"Empty delegate account"
+      ~description:
+        "Cannot register a delegate when its implicit account is empty"
+      ~pp:(fun ppf delegate ->
+        Format.fprintf
+          ppf
+          "Delegate registration is forbidden when the delegate\n\
+          \           implicit account is empty (%a)"
+          Signature.Public_key_hash.pp
+          delegate)
+      Data_encoding.(obj1 (req "delegate" Signature.Public_key_hash.encoding))
+      (function Empty_delegate_account c -> Some c | _ -> None)
+      (fun c -> Empty_delegate_account c)
+
+  let set_self_delegate c delegate =
+    let open Lwt_tzresult_syntax in
+    let*! is_registered = registered c delegate in
+    if is_registered then
+      let* () =
+        let* is_inactive = Delegate_activation_storage.is_inactive c delegate in
+        fail_unless is_inactive Active_delegate
       in
-      if (not known_delegate) || not (registered_delegate || self_delegation)
-      then fail (Unregistered_delegate delegate)
-      else
-        Contract_delegate_storage.find c contract >>=? fun current_delegate ->
-        (match current_delegate with
-        | Some current_delegate
-          when Signature.Public_key_hash.equal delegate current_delegate ->
-            if self_delegation then
-              Delegate_activation_storage.is_inactive c delegate >>=? function
-              | true -> return_unit
-              | false -> fail Active_delegate
-            else fail Current_delegate
-        | None | Some _ -> return_unit)
-        >>=? fun () ->
-        (* check if contract is a registered delegate *)
-        (match contract with
-        | Contract_repr.Implicit pkh ->
-            Contract_delegate_storage.registered c pkh >>=? fun is_registered ->
-            (* allow self-delegation to re-activate *)
-            if (not self_delegation) && is_registered then
-              fail (No_deletion pkh)
-            else return_unit
-        | Originated _ -> return_unit)
-        >>=? fun () ->
-        Contract_storage.allocated c contract >>= fun exists ->
-        error_when
-          (self_delegation && not exists)
-          (Empty_delegate_account delegate)
-        >>?= fun () ->
+      Stake_storage.set_active c delegate
+    else
+      let contract = Contract_repr.Implicit delegate in
+      let* () =
+        let* is_pk_revealed =
+          Contract_manager_storage.is_manager_key_revealed c delegate
+        in
+        fail_unless is_pk_revealed (Unregistered_delegate delegate)
+      in
+      let* () =
+        let*! is_allocated = Contract_storage.allocated c contract in
+        fail_unless is_allocated (Empty_delegate_account delegate)
+      in
+      let* balance_and_frozen_bonds =
         Contract_storage.get_balance_and_frozen_bonds c contract
-        >>=? fun balance_and_frozen_bonds ->
+      in
+      let* c =
         Stake_storage.remove_contract_stake c contract balance_and_frozen_bonds
-        >>=? fun c ->
-        Contract_delegate_storage.set c contract delegate >>=? fun c ->
-        Stake_storage.add_stake c delegate balance_and_frozen_bonds
-        >>=? fun c ->
-        if self_delegation then
-          Storage.Delegates.add c delegate >>= fun c -> set_active c delegate
-        else return c
+      in
+      let* c = Contract_delegate_storage.set c contract delegate in
+      let* c = Stake_storage.add_stake c delegate balance_and_frozen_bonds in
+      let*! c = Storage.Delegates.add c delegate in
+      let* c = Stake_storage.set_active c delegate in
+      return c
+
+  type error +=
+    | (* `Permanent *) No_deletion of Signature.Public_key_hash.t
+    | (* `Temporary *) Current_delegate
+
+  let () =
+    register_error_kind
+      `Permanent
+      ~id:"delegate.no_deletion"
+      ~title:"Forbidden delegate deletion"
+      ~description:"Tried to unregister a delegate"
+      ~pp:(fun ppf delegate ->
+        Format.fprintf
+          ppf
+          "Delegate deletion is forbidden (%a)"
+          Signature.Public_key_hash.pp
+          delegate)
+      Data_encoding.(obj1 (req "delegate" Signature.Public_key_hash.encoding))
+      (function No_deletion c -> Some c | _ -> None)
+      (fun c -> No_deletion c) ;
+    register_error_kind
+      `Temporary
+      ~id:"delegate.unchanged"
+      ~title:"Unchanged delegated"
+      ~description:"Contract already delegated to the given delegate"
+      ~pp:(fun ppf () ->
+        Format.fprintf
+          ppf
+          "The contract is already delegated to the same delegate")
+      Data_encoding.empty
+      (function Current_delegate -> Some () | _ -> None)
+      (fun () -> Current_delegate)
+
+  let set_delegate c contract delegate =
+    let open Lwt_tzresult_syntax in
+    let* () =
+      match contract with
+      | Contract_repr.Originated _ -> return_unit
+      | Implicit pkh ->
+          let*! is_registered = registered c pkh in
+          fail_when is_registered (No_deletion pkh)
+    in
+    let* () =
+      let* current_delegate = Contract_delegate_storage.find c contract in
+      match (delegate, current_delegate) with
+      | None, None ->
+          (* we don't fail in this case in order not to risk breaking
+             existing smart contracts. *)
+          return_unit
+      | Some delegate, Some current_delegate
+        when Signature.Public_key_hash.equal delegate current_delegate ->
+          fail Current_delegate
+      | _ -> return_unit
+    in
+    let* balance_and_frozen_bonds =
+      Contract_storage.get_balance_and_frozen_bonds c contract
+    in
+    let* c =
+      Stake_storage.remove_contract_stake c contract balance_and_frozen_bonds
+    in
+    match delegate with
+    | None ->
+        let* c = Contract_delegate_storage.delete c contract in
+        return c
+    | Some delegate ->
+        let* () =
+          let*! is_delegate_registered = registered c delegate in
+          fail_when
+            (not is_delegate_registered)
+            (Unregistered_delegate delegate)
+        in
+        let* c = Contract_delegate_storage.set c contract delegate in
+        let* c = Stake_storage.add_stake c delegate balance_and_frozen_bonds in
+        return c
+
+  let set c contract delegate =
+    match (delegate, contract) with
+    | Some delegate, Contract_repr.Implicit source
+      when Signature.Public_key_hash.equal source delegate ->
+        set_self_delegate c delegate
+    | _ -> set_delegate c contract delegate
+end
 
 let fold = Storage.Delegates.fold
 
@@ -215,7 +230,7 @@ let spendable_balance ctxt delegate =
   Storage.Contract.Spendable_balance.get ctxt contract
 
 let staking_balance ctxt delegate =
-  Contract_delegate_storage.registered ctxt delegate >>=? fun is_registered ->
+  registered ctxt delegate >>= fun is_registered ->
   if is_registered then Stake_storage.get_staking_balance ctxt delegate
   else return Tez_repr.zero
 
diff --git a/src/proto_alpha/lib_protocol/delegate_storage.mli b/src/proto_alpha/lib_protocol/delegate_storage.mli
index 78eadc0204a93579e178d132c306a57b86c65c64..784d7732f492b8c411fe88145fcf5c2f5a3836cf 100644
--- a/src/proto_alpha/lib_protocol/delegate_storage.mli
+++ b/src/proto_alpha/lib_protocol/delegate_storage.mli
@@ -26,6 +26,7 @@
 (*****************************************************************************)
 
 (** This module groups everything related to delegate registration.
+    For the invariants maintained, see the submodule {!Contract}.
 
     It also groups "trivial" getters/setters related to delegates.
 
@@ -35,34 +36,59 @@
 *)
 
 type error +=
-  | (* `Permanent *) No_deletion of Signature.Public_key_hash.t
-  | (* `Temporary *) Active_delegate
-  | (* `Temporary *) Current_delegate
-  | (* `Permanent *) Empty_delegate_account of Signature.Public_key_hash.t
   | (* `Permanent *) Unregistered_delegate of Signature.Public_key_hash.t
 
-val set_active :
-  Raw_context.t -> Signature.Public_key_hash.t -> Raw_context.t tzresult Lwt.t
-
-val set_inactive :
-  Raw_context.t -> Signature.Public_key_hash.t -> Raw_context.t tzresult Lwt.t
-
-val deactivated :
-  Raw_context.t -> Signature.Public_key_hash.t -> bool tzresult Lwt.t
-
-(** Allow to register a delegate when creating an account. *)
-val init :
-  Raw_context.t ->
-  Contract_repr.t ->
-  Signature.Public_key_hash.t ->
-  Raw_context.t tzresult Lwt.t
-
-(** Allow to set the delegate of an account. *)
-val set :
-  Raw_context.t ->
-  Contract_repr.t ->
-  Signature.Public_key_hash.t option ->
-  Raw_context.t tzresult Lwt.t
+(** This module ensures the following invariants:
+    - registered delegates (i.e. those that appear in {!Storage.Delegates}) are
+    self-delegated, that is a delegate's implicit account delegates to itself
+    (i.e. {!Contract_delegate_storage.find} [delegate] returns [delegate]),
+    - registered delegates have their public keys revealed,
+    - registered delegates cannot change their delegation,
+    - stake is properly moved when changing delegation.
+*)
+module Contract : sig
+  type error +=
+    | (* `Temporary *) Active_delegate
+    | (* `Permanent *) Empty_delegate_account of Signature.Public_key_hash.t
+    | (* `Permanent *) No_deletion of Signature.Public_key_hash.t
+    | (* `Temporary *) Current_delegate
+
+  (** [init ctxt contract delegate] registers a delegate when
+      creating a contract.
+
+      This functions assumes that [contract] is allocated.
+
+      This function returns the {!Unregistered_delegate} error
+      if [contract] already has a delegate or
+      if [delegate] is not a registered delegate. *)
+  val init :
+    Raw_context.t ->
+    Contract_repr.t ->
+    Signature.Public_key_hash.t ->
+    Raw_context.t tzresult Lwt.t
+
+  (** [set ctxt contract delegate_opt] allows to set the
+      delegate of a contract to [delegate] when [delegate_opt = Some delegate]
+      or to unset the delegate when [delegate_opt = None].
+      When [delegate_opt = Some contract] (aka self-delegation),
+      the function also registers the contract as a delegate and
+      sets the delegate as {{!module:Delegate_activation_storage}active}.
+
+      It returns the {!Unregistered_delegate} error when self-delegating and when the public key is not yet revealed.
+      It returns the {!Empty_delegate_account} error when self-delegating and the implicit account is not {{!Contract_storage.allocated}allocated}.
+      It returns the {!Active_delegate} error when self-delegating and the delegate is already active.
+      It returns the {!Unregistered_delegate} error when trying to set the delegate to an unregistered delegate.
+      It returns the {!Current_delegate} error when contract is already delegated to the same delegate.
+      It returns the {!No_deletion} error when trying to unset or change the delegate of a registered delegate. *)
+  val set :
+    Raw_context.t ->
+    Contract_repr.t ->
+    Signature.Public_key_hash.t option ->
+    Raw_context.t tzresult Lwt.t
+end
+
+(** Has a delegate been registered in the delegate table? *)
+val registered : Raw_context.t -> Signature.Public_key_hash.t -> bool Lwt.t
 
 (** Iterate on all registered delegates. *)
 val fold :
diff --git a/src/proto_alpha/lib_protocol/stake_storage.ml b/src/proto_alpha/lib_protocol/stake_storage.ml
index 76e3f1bf6ec8ba567143e2290f19bc750e368fa1..08549fa26a2c5bc84bd10820600bcbbe8fc2b714 100644
--- a/src/proto_alpha/lib_protocol/stake_storage.ml
+++ b/src/proto_alpha/lib_protocol/stake_storage.ml
@@ -107,16 +107,21 @@ let add_stake ctxt delegate amount =
        would also have it now). *)
     return ctxt
 
-let deactivate_only_call_from_delegate_storage ctxt delegate =
+let set_inactive ctxt delegate =
+  Delegate_activation_storage.set_inactive ctxt delegate >>= fun ctxt ->
   Storage.Stake.Active_delegates_with_minimal_stake.remove ctxt delegate
 
-let activate_only_call_from_delegate_storage ctxt delegate =
-  get_initialized_stake ctxt delegate >>=? fun (staking_balance, ctxt) ->
-  let minimal_stake = Constants_storage.minimal_stake ctxt in
-  if Tez_repr.(staking_balance >= minimal_stake) then
-    Storage.Stake.Active_delegates_with_minimal_stake.add ctxt delegate ()
-    >>= fun ctxt -> return ctxt
-  else return ctxt
+let set_active ctxt delegate =
+  Delegate_activation_storage.set_active ctxt delegate
+  >>=? fun (ctxt, inactive) ->
+  if not inactive then return ctxt
+  else
+    get_initialized_stake ctxt delegate >>=? fun (staking_balance, ctxt) ->
+    let minimal_stake = Constants_storage.minimal_stake ctxt in
+    if Tez_repr.(staking_balance >= minimal_stake) then
+      Storage.Stake.Active_delegates_with_minimal_stake.add ctxt delegate ()
+      >>= fun ctxt -> return ctxt
+    else return ctxt
 
 let snapshot ctxt =
   Storage.Stake.Last_snapshot.get ctxt >>=? fun index ->
diff --git a/src/proto_alpha/lib_protocol/stake_storage.mli b/src/proto_alpha/lib_protocol/stake_storage.mli
index 84e7e67ab64ae08bb6f74dc06e66a0d3ff73d02b..515d001f2f2fe9823f00beb0acf33116923afea2 100644
--- a/src/proto_alpha/lib_protocol/stake_storage.mli
+++ b/src/proto_alpha/lib_protocol/stake_storage.mli
@@ -46,10 +46,10 @@ val add_stake :
   Tez_repr.t ->
   Raw_context.t tzresult Lwt.t
 
-val deactivate_only_call_from_delegate_storage :
+val set_inactive :
   Raw_context.t -> Signature.Public_key_hash.t -> Raw_context.t Lwt.t
 
-val activate_only_call_from_delegate_storage :
+val set_active :
   Raw_context.t -> Signature.Public_key_hash.t -> Raw_context.t tzresult Lwt.t
 
 val get_staking_balance :
diff --git a/src/proto_alpha/lib_protocol/test/integration/consensus/test_delegation.ml b/src/proto_alpha/lib_protocol/test/integration/consensus/test_delegation.ml
index 880961fcc6cdfc4ec1a5ab890de1895a855c8428..101f50fb89c2713ceb1f8e25c640c9aa53a52c4e 100644
--- a/src/proto_alpha/lib_protocol/test/integration/consensus/test_delegation.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/consensus/test_delegation.ml
@@ -56,7 +56,7 @@ let expect_error err = function
 let expect_alpha_error err = expect_error (Environment.Ecoproto_error err)
 
 let expect_no_change_registered_delegate_pkh pkh = function
-  | Environment.Ecoproto_error (Delegate_storage.No_deletion pkh0) :: _
+  | Environment.Ecoproto_error (Delegate_storage.Contract.No_deletion pkh0) :: _
     when pkh0 = pkh ->
       return_unit
   | _ -> failwith "Delegate can not be deleted and operation should fail."
@@ -221,7 +221,8 @@ let bootstrap_manager_already_registered_delegate ~fee () =
   else
     Incremental.add_operation
       ~expect_apply_failure:(function
-        | Environment.Ecoproto_error Delegate_storage.Active_delegate :: _ ->
+        | Environment.Ecoproto_error Delegate_storage.Contract.Active_delegate
+          :: _ ->
             return_unit
         | _ -> failwith "Delegate is already active and operation should fail.")
       i
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml
index 772137cfa47585f4fd9422a4426eb404059a4ff1..1ca7ec09ae115c80a9fc2aecd9c01ec1e1695c90 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml
@@ -335,6 +335,16 @@ let wrong_voting_period_kind loc = function
   | [Environment.Ecoproto_error (Wrong_voting_period_kind _)] -> return_unit
   | err -> wrong_error "Wrong_voting_period_kind" err loc
 
+let proposals_from_unregistered_delegate loc = function
+  | [Environment.Ecoproto_error (Proposals_from_unregistered_delegate _)] ->
+      return_unit
+  | err -> wrong_error "Proposals_from_unregistered_delegate" err loc
+
+let ballot_from_unregistered_delegate loc = function
+  | [Environment.Ecoproto_error (Ballot_from_unregistered_delegate _)] ->
+      return_unit
+  | err -> wrong_error "Ballot_from_unregistered_delegate" err loc
+
 let source_not_in_vote_listings loc = function
   | [Environment.Ecoproto_error Source_not_in_vote_listings] -> return_unit
   | err -> wrong_error "Source_not_in_vote_listings" err loc
@@ -1330,6 +1340,13 @@ let test_proposals_source_not_in_vote_listings () =
   let* block, funder = context_init1 ~blocks_per_cycle:10l () in
   let fresh_account = Account.new_account () in
   let proposer = Contract.Implicit fresh_account.pkh in
+  let assert_fails_with_unregistered_delegate block =
+    assert_validate_proposals_fails
+      ~expected_error:proposals_from_unregistered_delegate
+      ~proposer
+      ~proposals:[Protocol_hash.zero]
+      block
+  in
   let assert_fails_with_source_not_in_vote_listings block =
     assert_validate_proposals_fails
       ~expected_error:source_not_in_vote_listings
@@ -1338,15 +1355,15 @@ let test_proposals_source_not_in_vote_listings () =
       block
   in
   (* Fail when the source has no contract in the storage. *)
-  let* () = assert_fails_with_source_not_in_vote_listings block __LOC__ in
+  let* () = assert_fails_with_unregistered_delegate block __LOC__ in
   let* operation = Op.transaction (B block) funder proposer Tez.one in
   let* block = Block.bake block ~operation in
   (* Fail when the contract's public key is unreavealed. *)
-  let* () = assert_fails_with_source_not_in_vote_listings block __LOC__ in
+  let* () = assert_fails_with_unregistered_delegate block __LOC__ in
   let* operation = Op.revelation (B block) fresh_account.pk in
   let* block = Block.bake block ~operation in
   (* Fail when the source is not a delegate. *)
-  let* () = assert_fails_with_source_not_in_vote_listings block __LOC__ in
+  let* () = assert_fails_with_unregistered_delegate block __LOC__ in
   let* operation = Op.delegation (B block) proposer (Some fresh_account.pkh) in
   let* block = Block.bake block ~operation in
   (* Fail when the source is a delegate, but not yet in the vote listings. *)
@@ -1790,16 +1807,24 @@ let test_ballot_source_not_in_vote_listings () =
       ~ballot:Vote.Yay
       block
   in
+  let assert_fails_with_unregistered_delegate block =
+    assert_validate_ballot_fails
+      ~expected_error:ballot_from_unregistered_delegate
+      ~voter
+      ~proposal
+      ~ballot:Vote.Yay
+      block
+  in
   (* Fail when the source has no contract in the storage. *)
-  let* () = assert_fails_with_source_not_in_vote_listings block __LOC__ in
+  let* () = assert_fails_with_unregistered_delegate block __LOC__ in
   let* operation = Op.transaction (B block) funder voter Tez.one in
   let* block = Block.bake block ~operation in
   (* Fail when the contract's public key is unreavealed. *)
-  let* () = assert_fails_with_source_not_in_vote_listings block __LOC__ in
+  let* () = assert_fails_with_unregistered_delegate block __LOC__ in
   let* operation = Op.revelation (B block) fresh_account.pk in
   let* block = Block.bake block ~operation in
   (* Fail when the source is not a delegate. *)
-  let* () = assert_fails_with_source_not_in_vote_listings block __LOC__ in
+  let* () = assert_fails_with_unregistered_delegate block __LOC__ in
   let* operation = Op.delegation (B block) voter (Some fresh_account.pkh) in
   let* block = Block.bake block ~operation in
   (* Fail when the source is a delegate, but not yet in the vote listings. *)
diff --git a/src/proto_alpha/lib_protocol/test/integration/test_frozen_bonds.ml b/src/proto_alpha/lib_protocol/test/integration/test_frozen_bonds.ml
index 3717b5e8317a35d12345e255f27a2ce4e003b520..3704c98b187e5275181a71d62be0eb2f89fb3b03 100644
--- a/src/proto_alpha/lib_protocol/test/integration/test_frozen_bonds.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/test_frozen_bonds.ml
@@ -93,7 +93,7 @@ let init_test ~user_is_delegate =
   (* Configure delegate, as a delegate by self-delegation, for which
      revealing its manager key is a prerequisite. *)
   Contract.reveal_manager_key ctxt delegate delegate_pk >>>=? fun ctxt ->
-  Delegate.set ctxt delegate_contract (Some delegate) >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt delegate_contract (Some delegate) >>>=? fun ctxt ->
   return (ctxt, user_contract, user_account, delegate)
 
 (** Tested scenario :
@@ -111,7 +111,7 @@ let test_delegate_then_freeze_deposit () =
   (* Fetch user's initial balance before freeze. *)
   Token.balance ctxt user_account >>>=? fun (ctxt, user_balance) ->
   (* Let user delegate to "delegate". *)
-  Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
   (* Fetch staking balance after delegation and before freeze. *)
   Delegate.staking_balance ctxt delegate >>>=? fun staking_balance ->
   (* Freeze a tx-rollup deposit. *)
@@ -126,7 +126,7 @@ let test_delegate_then_freeze_deposit () =
   (* Ensure staking balance did not change. *)
   Assert.equal_tez ~loc:__LOC__ staking_balance' staking_balance >>=? fun () ->
   (* Remove delegation. *)
-  Delegate.set ctxt user_contract None >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt user_contract None >>>=? fun ctxt ->
   (* Fetch staking balance after delegation removal. *)
   Delegate.staking_balance ctxt delegate >>>=? fun staking_balance'' ->
   (* Ensure staking balance decreased by user's initial balance. *)
@@ -173,7 +173,7 @@ let test_freeze_deposit_then_delegate () =
      Now, fetch staking balance before delegation and after freeze. *)
   Delegate.staking_balance ctxt delegate >>>=? fun staking_balance ->
   (* Let user delegate to "delegate". *)
-  Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
   (* Fetch staking balance after delegation. *)
   Delegate.staking_balance ctxt delegate >>>=? fun staking_balance' ->
   (* ensure staking balance increased by the user's balance. *)
@@ -191,7 +191,7 @@ let test_freeze_deposit_then_delegate () =
   Assert.equal_tez ~loc:__LOC__ staking_balance'' staking_balance'
   >>=? fun () ->
   (* Remove delegation. *)
-  Delegate.set ctxt user_contract None >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt user_contract None >>>=? fun ctxt ->
   (* Fetch staking balance. *)
   Delegate.staking_balance ctxt delegate >>>=? fun staking_balance''' ->
   (* Check that staking balance has decreased by the user's initial balance. *)
@@ -341,7 +341,7 @@ let test_delegated_balance () =
   (* Check that the delegated balance of [delegate] is null. *)
   check_delegated_balance_is ctxt ~loc:__LOC__ delegate Tez.zero >>=? fun () ->
   (* Let user delegate to "delegate". *)
-  Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
   (* Fetch staking balance after delegation. *)
   Delegate.staking_balance ctxt delegate >>>=? fun staking_balance' ->
   (* ensure staking balance increased by the user's balance. *)
@@ -365,7 +365,7 @@ let test_delegated_balance () =
   check_delegated_balance_is ctxt ~loc:__LOC__ delegate user_balance
   >>=? fun () ->
   (* Remove delegation. *)
-  Delegate.set ctxt user_contract None >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt user_contract None >>>=? fun ctxt ->
   (* Fetch staking balance. *)
   Delegate.staking_balance ctxt delegate >>>=? fun staking_balance''' ->
   (* Check that staking balance has decreased by the user's initial balance. *)
@@ -407,7 +407,8 @@ let test_scenario scenario =
   (* Configure delegate, as a delegate by self-delegation, for which
      revealing its manager key is a prerequisite. *)
   Contract.reveal_manager_key ctxt delegate2 delegate_pk2 >>>=? fun ctxt ->
-  Delegate.set ctxt delegate_contract2 (Some delegate2) >>>=? fun ctxt ->
+  Contract.Delegate.set ctxt delegate_contract2 (Some delegate2)
+  >>>=? fun ctxt ->
   let tx_rollup1, nonce = mk_tx_rollup () in
   let tx_rollup2, _ = mk_tx_rollup ~nonce () in
   let bond_id1 = Bond_id.Tx_rollup_bond_id tx_rollup1 in
@@ -422,7 +423,7 @@ let test_scenario scenario =
     Contract.get_balance_and_frozen_bonds ctxt user_contract
     >>>=? fun user_balance ->
     (* Let user delegate to "delegate". *)
-    Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
+    Contract.Delegate.set ctxt user_contract (Some delegate) >>>=? fun ctxt ->
     (* Fetch staking balance after delegation  *)
     Delegate.staking_balance ctxt delegate >>>=? fun staking_balance' ->
     Assert.equal_tez
@@ -496,7 +497,7 @@ let test_scenario scenario =
     (* Fetch user's initial balance before undelegate. *)
     Token.balance ctxt user_account >>>=? fun (_, user_balance) ->
     (* Remove delegation. *)
-    Delegate.set ctxt user_contract None >>>=? fun ctxt ->
+    Contract.Delegate.set ctxt user_contract None >>>=? fun ctxt ->
     (* Fetch staking balance after delegation removal. *)
     Delegate.staking_balance ctxt delegate >>>=? fun staking_balance' ->
     (* Ensure staking balance decreased by delegation amount *)
diff --git a/src/proto_alpha/lib_protocol/test/integration/test_token.ml b/src/proto_alpha/lib_protocol/test/integration/test_token.ml
index 4a05fb1a885e7d9e132c526f87c3b45bc7ec7193..1d3edd5f6c2f7db8e5f0bdc89c0ed23e73c6913a 100644
--- a/src/proto_alpha/lib_protocol/test/integration/test_token.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/test_token.ml
@@ -516,13 +516,13 @@ let build_test_cases () =
   (* Configure baker1, and baker2 as delegates by self-delegation, for which
      revealing their manager key is a prerequisite. *)
   wrap (Contract.reveal_manager_key ctxt baker1 baker1_pk) >>=? fun ctxt ->
-  wrap (Delegate.set ctxt (Contract.Implicit baker1) (Some baker1))
+  wrap (Contract.Delegate.set ctxt (Contract.Implicit baker1) (Some baker1))
   >>=? fun ctxt ->
   wrap (Contract.reveal_manager_key ctxt baker2 baker2_pk) >>=? fun ctxt ->
-  wrap (Delegate.set ctxt (Contract.Implicit baker2) (Some baker2))
+  wrap (Contract.Delegate.set ctxt (Contract.Implicit baker2) (Some baker2))
   (* Let user1 delegate to baker2. *)
   >>=? fun ctxt ->
-  wrap (Delegate.set ctxt (Contract.Implicit user1) (Some baker2))
+  wrap (Contract.Delegate.set ctxt (Contract.Implicit user1) (Some baker2))
   >>=? fun ctxt ->
   let tx_rollup1 = mk_rollup () in
   let bond_id1 = Bond_id.Tx_rollup_bond_id tx_rollup1 in
diff --git a/src/proto_alpha/lib_protocol/validate_errors.ml b/src/proto_alpha/lib_protocol/validate_errors.ml
index 00f517d5a3c5ae9abc07c39d52105ec3d1d2107e..eb7e00753be8eb4f407a8b23eed5b55dea0e4293 100644
--- a/src/proto_alpha/lib_protocol/validate_errors.ml
+++ b/src/proto_alpha/lib_protocol/validate_errors.ml
@@ -411,6 +411,7 @@ module Voting = struct
     | Conflicting_dictator_proposals of Operation_hash.t
     | Testnet_dictator_multiple_proposals
     | Testnet_dictator_conflicting_operation
+    | Proposals_from_unregistered_delegate of Signature.Public_key_hash.t
     | (* Ballot errors *)
         Ballot_for_wrong_proposal of {
         current : Protocol_hash.t;
@@ -418,6 +419,7 @@ module Voting = struct
       }
     | Already_submitted_a_ballot
     | Conflicting_ballot of {conflicting_operation : Operation_hash.t}
+    | Ballot_from_unregistered_delegate of Signature.Public_key_hash.t
 
   let () =
     (* Shared voting errors *)
@@ -666,6 +668,21 @@ module Voting = struct
       Data_encoding.empty
       (function Testnet_dictator_conflicting_operation -> Some () | _ -> None)
       (fun () -> Testnet_dictator_conflicting_operation) ;
+    register_error_kind
+      `Permanent
+      ~id:"operation.proposals_from_unregistered_delegate"
+      ~title:"Proposals from an unregistered delegate"
+      ~description:"Cannot submit proposals with an unregistered delegate."
+      ~pp:(fun ppf c ->
+        Format.fprintf
+          ppf
+          "Cannot submit proposals with public key hash %a (unregistered \
+           delegate)."
+          Signature.Public_key_hash.pp
+          c)
+      Data_encoding.(obj1 (req "delegate" Signature.Public_key_hash.encoding))
+      (function Proposals_from_unregistered_delegate c -> Some c | _ -> None)
+      (fun c -> Proposals_from_unregistered_delegate c) ;
 
     (* Ballot errors *)
     register_error_kind
@@ -723,7 +740,21 @@ module Voting = struct
         | Conflicting_ballot {conflicting_operation} ->
             Some conflicting_operation
         | _ -> None)
-      (fun conflicting_operation -> Conflicting_ballot {conflicting_operation})
+      (fun conflicting_operation -> Conflicting_ballot {conflicting_operation}) ;
+    register_error_kind
+      `Permanent
+      ~id:"operation.ballot_from_unregistered_delegate"
+      ~title:"Ballot from an unregistered delegate"
+      ~description:"Cannot cast a ballot for an unregistered delegate."
+      ~pp:(fun ppf c ->
+        Format.fprintf
+          ppf
+          "Cannot cast a ballot for public key hash %a (unregistered delegate)."
+          Signature.Public_key_hash.pp
+          c)
+      Data_encoding.(obj1 (req "delegate" Signature.Public_key_hash.encoding))
+      (function Ballot_from_unregistered_delegate c -> Some c | _ -> None)
+      (fun c -> Ballot_from_unregistered_delegate c)
 end
 
 module Anonymous = struct
diff --git a/src/proto_alpha/lib_protocol/validate_errors.mli b/src/proto_alpha/lib_protocol/validate_errors.mli
index 2d52451bdf471e8844f07edc872df98bd4da9f4a..d83d9fdb111f44937cb792019a30d590cea58ed7 100644
--- a/src/proto_alpha/lib_protocol/validate_errors.mli
+++ b/src/proto_alpha/lib_protocol/validate_errors.mli
@@ -113,6 +113,7 @@ module Voting : sig
     | Conflicting_dictator_proposals of Operation_hash.t
     | Testnet_dictator_multiple_proposals
     | Testnet_dictator_conflicting_operation
+    | Proposals_from_unregistered_delegate of Signature.Public_key_hash.t
     | (* Ballot errors *)
         Ballot_for_wrong_proposal of {
         current : Protocol_hash.t;
@@ -120,6 +121,7 @@ module Voting : sig
       }
     | Already_submitted_a_ballot
     | Conflicting_ballot of {conflicting_operation : Operation_hash.t}
+    | Ballot_from_unregistered_delegate of Signature.Public_key_hash.t
 end
 
 (** Errors that may arise while validating an anonymous operation. *)
diff --git a/src/proto_alpha/lib_protocol/validate_operation.ml b/src/proto_alpha/lib_protocol/validate_operation.ml
index 94d3b45d03da8a23e19250be0aed1d6a6b7a30a6..6c9a67ade92a297528a7f97e548a0046fd08d6f6 100644
--- a/src/proto_alpha/lib_protocol/validate_operation.ml
+++ b/src/proto_alpha/lib_protocol/validate_operation.ml
@@ -964,6 +964,11 @@ module Voting = struct
       Compare.Int32.(expected = period_index)
       (Wrong_voting_period_index {expected; provided = period_index})
 
+  let check_proposals_source_is_registered ctxt source =
+    let open Lwt_tzresult_syntax in
+    let*! is_registered = Delegate.registered ctxt source in
+    fail_unless is_registered (Proposals_from_unregistered_delegate source)
+
   (** Check that the list of proposals is not empty and does not contain
     duplicates. *)
   let check_proposal_list_sanity proposals =
@@ -1034,12 +1039,20 @@ module Voting = struct
     let*! has_ballot = Vote.has_recorded_ballot ctxt source in
     fail_when has_ballot Already_submitted_a_ballot
 
+  let check_ballot_source_is_registered ctxt source =
+    let open Lwt_tzresult_syntax in
+    let*! is_registered = Delegate.registered ctxt source in
+    fail_unless is_registered (Ballot_from_unregistered_delegate source)
+
   (** Check that a Proposals operation can be safely applied.
 
     @return [Error Wrong_voting_period_index] if the operation's
     period and the [context]'s current period do not have the same
     index.
 
+    @return [Error Proposals_from_unregistered_delegate] if the
+    source is not a registered delegate.
+
     @return [Error Empty_proposals] if the list of proposals is empty.
 
     @return [Error Proposals_contain_duplicate] if the list of
@@ -1099,6 +1112,7 @@ module Voting = struct
              vs.voting_state
              oph)
       else
+        let* () = check_proposals_source_is_registered vi.ctxt source in
         let*? () = check_proposal_list_sanity proposals in
         let*? () = check_period_kind_for_proposals current_period in
         let* () = check_in_listings vi.ctxt source in
@@ -1131,6 +1145,9 @@ module Voting = struct
 
   (** Check that a Ballot operation can be safely applied.
 
+    @return [Error Ballot_from_unregistered_delegate] if the
+    source is not a registered delegate.
+
     @return [Error Conflicting_ballot] if the source has already
     submitted a ballot in the current block/mempool.
 
@@ -1163,6 +1180,7 @@ module Voting = struct
     let (Single (Ballot {source; period; proposal; ballot = _})) =
       operation.protocol_data.contents
     in
+    let* () = check_ballot_source_is_registered vi.ctxt source in
     let*? () = check_ballot_conflicts vs.voting_state source in
     let* current_period = Voting_period.get_current vi.ctxt in
     let*? () = check_period_index ~expected:current_period.index period in