diff --git a/src/hash.ml b/src/hash.ml
index cfaf5836..72a1d557 100644
--- a/src/hash.ml
+++ b/src/hash.ml
@@ -16,7 +16,7 @@ module type S = sig
   val to_b32 : t -> B32.t
 end
 
-module H32 = struct
+module H32 : S = struct
   type t = SHA256.t
 
   let hash s = SHA256.(digest_string s)
@@ -34,7 +34,7 @@ module H32 = struct
     let open Bin in
     map (bytes 32) of_octets to_octets
 
-  (* hashes are not b32 encoded in the database *)
+  (* hashs are not b32 encoded in the database *)
   let caqti =
     let open Caqti_type in
     custom
@@ -45,7 +45,7 @@ module H32 = struct
   let jsont = Jsont.of_of_string ~kind:"Hash 32" of_b32 ~enc:to_b32
 end
 
-module H64 = struct
+module H64 : S = struct
   type t = SHA512.t
 
   let hash s = SHA512.(digest_string s)
@@ -63,7 +63,6 @@ module H64 = struct
     let open Bin in
     map (bytes 64) of_octets to_octets
 
-  (* hashes are not b32 encoded in the database *)
   let caqti =
     let open Caqti_type in
     custom
@@ -74,20 +73,16 @@ module H64 = struct
   let jsont = Jsont.of_of_string ~kind:"Hash 64" of_b32 ~enc:to_b32
 end
 
-(* C-terminated strings
-   some strings need to be hashed with a '\0' termination char *)
-module Cstring = struct
-  module H32 = struct
-    include H32
+module H32_cstring : S = struct
+  include H32
 
-    let hash s = hash (s ^ "\x00")
-  end
+  let hash s = hash (s ^ "\x00")
+end
 
-  module H64 = struct
-    include H64
+module H64_cstring : S = struct
+  include H64
 
-    let hash s = hash (s ^ "\x00")
-  end
+  let hash s = hash (s ^ "\x00")
 end
 
 (* TODO
diff --git a/src/keys.ml b/src/keys.ml
index e2f7dc37..97b6f86c 100644
--- a/src/keys.ml
+++ b/src/keys.ml
@@ -160,7 +160,7 @@ module Make (Conn : Pg.CONN) (Fs : Fat.FS) : S = struct
       signf Sm_rsa.sign_secmod
         {
           h_denom_pub= h_pub;
-          h_section_name= Hash.Cstring.H64.hash section_name;
+          h_section_name= Hash.H64_cstring.hash section_name;
           anchor_time= stamp_start;
           duration_withdraw= Timestamp.diff stamp_start stamp_expire_withdraw;
         }
diff --git a/src/mte_management.ml b/src/mte_management.ml
index d5fd44e2..cc453afc 100644
--- a/src/mte_management.ml
+++ b/src/mte_management.ml
@@ -108,7 +108,7 @@ module Auditors = struct
       {
         start_date= validity_start;
         auditor_pub;
-        h_auditor_url= Hash.Cstring.H64.hash auditor_url;
+        h_auditor_url= Hash.H64_cstring.hash auditor_url;
       }
 
   let do_ ~db_conn v =
@@ -204,7 +204,7 @@ module Wire_fee = struct
     let open Signatures.MasterWireFee in
     verify Config.master_public_key master_sig_wire
       {
-        h_wire_method= Hash.Cstring.H64.hash wire_method;
+        h_wire_method= Hash.H64_cstring.hash wire_method;
         start_date= fee_start;
         end_date= fee_end;
         wire_fee;
@@ -320,10 +320,10 @@ module Wire = struct
     in
     let h_wire_details = Hash.FullPaytoHash.hash payto_uri in
     let h_conversion_url =
-      Hash.Cstring.H64.hash ((* ?? *) Option.value ~default:"" conversion_url)
+      Hash.H64_cstring.hash ((* ?? *) Option.value ~default:"" conversion_url)
     in
-    let h_credit_restrictions = Hash.Cstring.H64.hash "" in
-    let h_debit_restrictions = Hash.Cstring.H64.hash "" in
+    let h_credit_restrictions = Hash.H64_cstring.hash "" in
+    let h_debit_restrictions = Hash.H64_cstring.hash "" in
     (* - *)
     let* () =
       let open Signatures.MasterWireDetails in
@@ -466,7 +466,7 @@ module Drain = struct
         wtid;
         date;
         amount;
-        h_section= Hash.Cstring.H64.hash debit_account_section;
+        h_section= Hash.H64_cstring.hash debit_account_section;
         h_payto= FullPaytoHash.hash credit_payto_uri;
       }
 
@@ -515,7 +515,7 @@ module AmlOfficer = struct
       {
         change_date;
         officer_pub;
-        h_officer_name= Hash.Cstring.H64.hash officer_name;
+        h_officer_name= Hash.H64_cstring.hash officer_name;
         is_active;
       }
 
@@ -558,7 +558,7 @@ module Partners = struct
         end_date;
         wad_frequency;
         wad_fee;
-        h_url= Hash.Cstring.H64.hash partner_base_url;
+        h_url= Hash.H64_cstring.hash partner_base_url;
       }
 
   let do_ ~db_conn v =
diff --git a/src/signatures.ml b/src/signatures.ml
index f727b5c2..c7a3db0b 100644
--- a/src/signatures.ml
+++ b/src/signatures.ml
@@ -180,7 +180,7 @@ module DenominationKeyAnnouncement = struct
     (* purpose = TALER_SIGNATURE_SM_RSA_DENOMINATION_KEY *)
     type r = {
       h_denom_pub: DenominationHash.t;
-      h_section_name: Hash.Cstring.H64.t;
+      h_section_name: Hash.H64_cstring.t;
       anchor_time: Timestamp.t;
       duration_withdraw: TimeRelative.t;
     }
@@ -195,7 +195,7 @@ module DenominationKeyAnnouncement = struct
           { h_denom_pub; h_section_name; anchor_time; duration_withdraw })
       |+ Purpose.field purpose
       |+ field DenominationHash.bin (fun t -> t.h_denom_pub)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_section_name)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_section_name)
       |+ field Timestamp.bin (fun t -> t.anchor_time)
       |+ field TimeRelative.bin (fun t -> t.duration_withdraw)
       |> sealr
@@ -365,7 +365,7 @@ module MasterAddAuditor = struct
     type r = {
       start_date: Timestamp.t;
       auditor_pub: AuditorPublicKeyP.t;
-      h_auditor_url: Hash.Cstring.H64.t;
+      h_auditor_url: Hash.H64_cstring.t;
     }
 
     let bin =
@@ -376,7 +376,7 @@ module MasterAddAuditor = struct
       |+ Purpose.field purpose
       |+ field Timestamp.bin (fun t -> t.start_date)
       |+ field AuditorPublicKeyP.bin (fun t -> t.auditor_pub)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_auditor_url)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_auditor_url)
       |> sealr
   end
 
@@ -464,9 +464,9 @@ module MasterWireDetails = struct
     (* purpose = TALER_SIGNATURE_MASTER_WIRE_DETAILS *)
     type r = {
       h_wire_details: FullPaytoHash.t;
-      h_conversion_url: Hash.Cstring.H64.t;
-      h_credit_restrictions: Hash.Cstring.H64.t;
-      h_debit_restrictions: Hash.Cstring.H64.t;
+      h_conversion_url: Hash.H64_cstring.t;
+      h_credit_restrictions: Hash.H64_cstring.t;
+      h_debit_restrictions: Hash.H64_cstring.t;
     }
 
     let bin =
@@ -488,9 +488,9 @@ module MasterWireDetails = struct
           })
       |+ Purpose.field purpose
       |+ field FullPaytoHash.bin (fun t -> t.h_wire_details)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_conversion_url)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_credit_restrictions)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_debit_restrictions)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_conversion_url)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_credit_restrictions)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_debit_restrictions)
       |> sealr
   end
 
@@ -503,9 +503,9 @@ module MasterAddWire = struct
     type r = {
       start_date: Timestamp.t;
       h_wire: FullPaytoHash.t;
-      h_conversion_url: Hash.Cstring.H64.t;
-      h_credit_restrictions: Hash.Cstring.H64.t;
-      h_debit_restrictions: Hash.Cstring.H64.t;
+      h_conversion_url: Hash.H64_cstring.t;
+      h_credit_restrictions: Hash.H64_cstring.t;
+      h_debit_restrictions: Hash.H64_cstring.t;
     }
 
     let bin =
@@ -530,9 +530,9 @@ module MasterAddWire = struct
       |+ Purpose.field _purpose
       |+ field Timestamp.bin (fun t -> t.start_date)
       |+ field FullPaytoHash.bin (fun t -> t.h_wire)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_conversion_url)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_credit_restrictions)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_debit_restrictions)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_conversion_url)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_credit_restrictions)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_debit_restrictions)
       |> sealr
   end
 
@@ -567,7 +567,7 @@ module MasterDrainProfit = struct
       wtid: WireTransferIdentifierRawP.t;
       date: Timestamp.t;
       amount: Amount.t;
-      h_section: Hash.Cstring.H64.t;
+      h_section: Hash.H64_cstring.t;
       h_payto: FullPaytoHash.t;
     }
 
@@ -580,7 +580,7 @@ module MasterDrainProfit = struct
       |+ field WireTransferIdentifierRawP.bin (fun t -> t.wtid)
       |+ field Timestamp.bin (fun t -> t.date)
       |+ field Amount.bin (fun t -> t.amount)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_section)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_section)
       |+ field FullPaytoHash.bin (fun t -> t.h_payto)
       |> sealr
   end
@@ -594,7 +594,7 @@ module MasterAmlOfficerStatus = struct
     type r = {
       change_date: Timestamp.t;
       officer_pub: AmlOfficerPublicKeyP.t;
-      h_officer_name: Hash.Cstring.H64.t;
+      h_officer_name: Hash.H64_cstring.t;
       is_active: int32;
     }
 
@@ -606,7 +606,7 @@ module MasterAmlOfficerStatus = struct
       |+ Purpose.field _purpose
       |+ field Timestamp.bin (fun t -> t.change_date)
       |+ field AmlOfficerPublicKeyP.bin (fun t -> t.officer_pub)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_officer_name)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_officer_name)
       |+ field beint32 (fun t -> t.is_active)
       |> sealr
   end
@@ -623,7 +623,7 @@ module PartnerConfiguration = struct
       end_date: Timestamp.t;
       wad_frequency: TimeRelative.t;
       wad_fee: Amount.t;
-      h_url: Hash.Cstring.H64.t;
+      h_url: Hash.H64_cstring.t;
     }
 
     let bin =
@@ -646,7 +646,7 @@ module PartnerConfiguration = struct
       |+ field Timestamp.bin (fun t -> t.end_date)
       |+ field TimeRelative.bin (fun t -> t.wad_frequency)
       |+ field Amount.bin (fun t -> t.wad_fee)
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_url)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_url)
       |> sealr
   end
 
@@ -657,7 +657,7 @@ module WadPartnerSignature = struct
   module R = struct
     (* purpose = TALER_SIGNATURE_MASTER_PARTNER_DETAILS *)
     type r = {
-      h_partner_base_url: Hash.Cstring.H64.t;
+      h_partner_base_url: Hash.H64_cstring.t;
       master_public_key: MasterPublicKeyP.t;
       start_date: Timestamp.t;
       end_date: Timestamp.t;
@@ -688,7 +688,7 @@ module WadPartnerSignature = struct
             wad_frequency;
           })
       |+ Purpose.field _purpose
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_partner_base_url)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_partner_base_url)
       |+ field MasterPublicKeyP.bin (fun t -> t.master_public_key)
       |+ field Timestamp.bin (fun t -> t.start_date)
       |+ field Timestamp.bin (fun t -> t.end_date)
@@ -704,7 +704,7 @@ module MasterWireFee = struct
   module R = struct
     (* purpose = TALER_SIGNATURE_MASTER_WIRE_FEES *)
     type r = {
-      h_wire_method: Hash.Cstring.H64.t;
+      h_wire_method: Hash.H64_cstring.t;
       start_date: Timestamp.t;
       end_date: Timestamp.t;
       wire_fee: Amount.t;
@@ -718,7 +718,7 @@ module MasterWireFee = struct
         (fun _purpose h_wire_method start_date end_date wire_fee closing_fee ->
           { h_wire_method; start_date; end_date; wire_fee; closing_fee })
       |+ Purpose.field _purpose
-      |+ field Hash.Cstring.H64.bin (fun t -> t.h_wire_method)
+      |+ field Hash.H64_cstring.bin (fun t -> t.h_wire_method)
       |+ field Timestamp.bin (fun t -> t.start_date)
       |+ field Timestamp.bin (fun t -> t.end_date)
       |+ field Amount.bin (fun t -> t.wire_fee)
@@ -733,7 +733,7 @@ module ExchangeKeyValidity = struct
   module R = struct
     (* purpose = TALER_SIGNATURE_AUDITOR_EXCHANGE_KEYS *)
     type r = {
-      auditor_url_hash: Hash.Cstring.H64.t;
+      auditor_url_hash: Hash.H64_cstring.t;
       master: MasterPublicKeyP.t;
       start: Timestamp.t;
       expire_withdraw: Timestamp.t;
@@ -778,7 +778,7 @@ module ExchangeKeyValidity = struct
             denom_hash;
           })
       |+ Purpose.field _purpose
-      |+ field Hash.Cstring.H64.bin (fun t -> t.auditor_url_hash)
+      |+ field Hash.H64_cstring.bin (fun t -> t.auditor_url_hash)
       |+ field MasterPublicKeyP.bin (fun t -> t.master)
       |+ field Timestamp.bin (fun t -> t.start)
       |+ field Timestamp.bin (fun t -> t.expire_withdraw)
@@ -887,7 +887,7 @@ module DepositRequest = struct
     amount_with_fee: Amount.t;
     deposit_fee: Amount.t;
     merchant: MerchantPublicKeyP.t;
-    wallet_data_hash: Hash.Cstring.H64.t;
+    wallet_data_hash: Hash.H64_cstring.t;
   }
 end
 
@@ -950,7 +950,7 @@ module WireDepositData = struct
     wire_fee: Amount.t;
     merchant_pub: MerchantPublicKeyP.t;
     h_wire: MerchantWireHash.t;
-    h_details: Hash.Cstring.H64.t;
+    h_details: Hash.H64_cstring.t;
   }
 end
 
@@ -1011,7 +1011,7 @@ end
 module MerchantRefundConfirmation = struct
   (* purpose = TALER_SIGNATURE_MERCHANT_REFUND_OK *)
   (* Hash of the order ID (a string), hashed without the 0-termination. *)
-  type t = { h_order_id: Hash.Cstring.H64.t }
+  type t = { h_order_id: Hash.H64_cstring.t }
 end
 
 module RecoupRequest = struct
@@ -1136,7 +1136,7 @@ module PurseDepositSignature = struct
     h_denom_pub: DenominationHash.t;
     h_age_commitment: AgeCommitmentHash.t;
     purse_pub: PursePublicKey.t;
-    h_exchange_base_url: Hash.Cstring.H64.t;
+    h_exchange_base_url: Hash.H64_cstring.t;
   }
 end
 
@@ -1203,7 +1203,7 @@ module WadDataSignature = struct
   type t = {
     wad_execution_time: Timestamp.t;
     total_amount: Amount.t;
-    h_items: Hash.Cstring.H64.t;
+    h_items: Hash.H64_cstring.t;
     wad_id: WadId.t;
   }
 end
@@ -1236,11 +1236,11 @@ end
 module AmlDecision = struct
   (* purpose = TALER_SIGNATURE_AML_DECISION *)
   type t = {
-    h_justification: Hash.Cstring.H64.t;
+    h_justification: Hash.H64_cstring.t;
     decision_time: Timestamp.t;
     new_threshold: Amount.t;
     h_payto: NormalizedPaytoHash.t;
-    h_kyc_requirements: Hash.Cstring.H64.t;
+    h_kyc_requirements: Hash.H64_cstring.t;
     new_state: int;
   }
 end
@@ -1267,7 +1267,7 @@ module ReserveAttestRequest = struct
   (* purpose = TALER_SIGNATURE_WALLET_ATTEST_REQUEST *)
   type t = {
     request_timestamp: Timestamp.t;
-    h_details: Hash.Cstring.H64.t;
+    h_details: Hash.H64_cstring.t;
   }
 end
 
@@ -1277,6 +1277,6 @@ module ExchangeAttest = struct
     attest_timestamp: Timestamp.t;
     expiration_time: Timestamp.t;
     reserve_pub: ReservePublicKeyP.t;
-    h_attributes: Hash.Cstring.H64.t;
+    h_attributes: Hash.H64_cstring.t;
   }
 end