diff --git a/src/proto_alpha/lib_protocol/src/TEZOS_PROTOCOL b/src/proto_alpha/lib_protocol/src/TEZOS_PROTOCOL
index d2e629b3a..32e82d17b 100644
--- a/src/proto_alpha/lib_protocol/src/TEZOS_PROTOCOL
+++ b/src/proto_alpha/lib_protocol/src/TEZOS_PROTOCOL
@@ -2,7 +2,10 @@
     "hash": "ProtoALphaALphaALphaALphaALphaALphaALphaALphaDdp3zK",
     "modules": [
         "Misc",
-        "Tezos_hash",
+        "State_hash",
+        "Nonce_hash",
+        "Script_expr_hash",
+        "Contract_hash",
 
         "Qty_repr",
         "Tez_repr",
diff --git a/src/proto_alpha/lib_protocol/src/alpha_context.ml b/src/proto_alpha/lib_protocol/src/alpha_context.ml
index fbdfbe237..3feafd805 100644
--- a/src/proto_alpha/lib_protocol/src/alpha_context.ml
+++ b/src/proto_alpha/lib_protocol/src/alpha_context.ml
@@ -54,8 +54,6 @@ type public_key_hash = Ed25519.Public_key_hash.t
 type secret_key = Ed25519.Secret_key.t
 type signature = Ed25519.Signature.t
 
-include Tezos_hash
-
 module Constants = struct
   include Constants_repr
   let cycle_length c =
diff --git a/src/proto_alpha/lib_protocol/src/alpha_context.mli b/src/proto_alpha/lib_protocol/src/alpha_context.mli
index a8f3245ec..6b29978e6 100644
--- a/src/proto_alpha/lib_protocol/src/alpha_context.mli
+++ b/src/proto_alpha/lib_protocol/src/alpha_context.mli
@@ -17,10 +17,6 @@ end
 type t
 type context = t
 
-module Contract_hash = Tezos_hash.Contract_hash
-
-module Nonce_hash = Tezos_hash.Nonce_hash
-
 type public_key = Ed25519.Public_key.t
 type public_key_hash = Ed25519.Public_key_hash.t
 type secret_key = Ed25519.Secret_key.t
diff --git a/src/proto_alpha/lib_protocol/src/block_header_repr.ml b/src/proto_alpha/lib_protocol/src/block_header_repr.ml
index 5265182b8..149d3af0c 100644
--- a/src/proto_alpha/lib_protocol/src/block_header_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/block_header_repr.ml
@@ -7,8 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-open Tezos_hash
-
 (** Block header *)
 
 (** Exported type *)
diff --git a/src/proto_alpha/lib_protocol/src/block_header_repr.mli b/src/proto_alpha/lib_protocol/src/block_header_repr.mli
index d84d9f4e9..2fad14041 100644
--- a/src/proto_alpha/lib_protocol/src/block_header_repr.mli
+++ b/src/proto_alpha/lib_protocol/src/block_header_repr.mli
@@ -7,8 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-open Tezos_hash
-
 (** Exported type *)
 type t = {
   shell: Block_header.shell_header ;
diff --git a/src/proto_alpha/lib_protocol/src/contract_hash.ml b/src/proto_alpha/lib_protocol/src/contract_hash.ml
new file mode 100644
index 000000000..689fee038
--- /dev/null
+++ b/src/proto_alpha/lib_protocol/src/contract_hash.ml
@@ -0,0 +1,21 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2018.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+(* 20 *)
+let contract_hash = "\003\099\029" (* TZ(36) *)
+
+include Blake2B.Make(Base58)(struct
+    let name = "Contract_hash"
+    let title = "A contract ID"
+    let b58check_prefix = contract_hash
+    let size = Some 20
+  end)
+
+let () =
+  Base58.check_encoded_prefix b58check_encoding "TZ1" 36
diff --git a/src/proto_alpha/lib_protocol/src/contract_repr.ml b/src/proto_alpha/lib_protocol/src/contract_repr.ml
index d70d6c85a..388d473c1 100644
--- a/src/proto_alpha/lib_protocol/src/contract_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/contract_repr.ml
@@ -7,8 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-open Tezos_hash
-
 type t =
   | Default of Ed25519.Public_key_hash.t
   | Originated of Contract_hash.t
diff --git a/src/proto_alpha/lib_protocol/src/contract_repr.mli b/src/proto_alpha/lib_protocol/src/contract_repr.mli
index 3fc41c9aa..5b5a100a1 100644
--- a/src/proto_alpha/lib_protocol/src/contract_repr.mli
+++ b/src/proto_alpha/lib_protocol/src/contract_repr.mli
@@ -7,8 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-open Tezos_hash
-
 type t = private
   | Default of Ed25519.Public_key_hash.t
   | Originated of Contract_hash.t
diff --git a/src/proto_alpha/lib_protocol/src/nonce_hash.ml b/src/proto_alpha/lib_protocol/src/nonce_hash.ml
new file mode 100644
index 000000000..eb5e46eab
--- /dev/null
+++ b/src/proto_alpha/lib_protocol/src/nonce_hash.ml
@@ -0,0 +1,21 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2018.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+(* 32 *)
+let nonce_hash = "\069\220\169" (* nce(53) *)
+
+include Blake2B.Make(Base58)(struct
+    let name = "cycle_nonce"
+    let title = "A nonce hash"
+    let b58check_prefix = nonce_hash
+    let size = None
+  end)
+
+let () =
+  Base58.check_encoded_prefix b58check_encoding "nce" 53
diff --git a/src/proto_alpha/lib_protocol/src/nonce_storage.ml b/src/proto_alpha/lib_protocol/src/nonce_storage.ml
index 800b87119..7b5521489 100644
--- a/src/proto_alpha/lib_protocol/src/nonce_storage.ml
+++ b/src/proto_alpha/lib_protocol/src/nonce_storage.ml
@@ -54,7 +54,7 @@ let reveal c level nonce =
 
 type status = Storage.Seed.nonce_status =
   | Unrevealed of {
-      nonce_hash: Tezos_hash.Nonce_hash.t ;
+      nonce_hash: Nonce_hash.t ;
       delegate_to_reward: Ed25519.Public_key_hash.t ;
       reward_amount: Tez_repr.t ;
     }
diff --git a/src/proto_alpha/lib_protocol/src/nonce_storage.mli b/src/proto_alpha/lib_protocol/src/nonce_storage.mli
index 1010818f4..836439b3c 100644
--- a/src/proto_alpha/lib_protocol/src/nonce_storage.mli
+++ b/src/proto_alpha/lib_protocol/src/nonce_storage.mli
@@ -7,8 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-open Tezos_hash
-
 type error +=
   | Too_late_revelation
   | Too_early_revelation
@@ -30,7 +28,7 @@ val reveal:
 
 type status =
   | Unrevealed of {
-      nonce_hash: Tezos_hash.Nonce_hash.t ;
+      nonce_hash: Nonce_hash.t ;
       delegate_to_reward: Ed25519.Public_key_hash.t ;
       reward_amount: Tez_repr.t ;
     }
diff --git a/src/proto_alpha/lib_protocol/src/script_expr_hash.ml b/src/proto_alpha/lib_protocol/src/script_expr_hash.ml
new file mode 100644
index 000000000..6257e1156
--- /dev/null
+++ b/src/proto_alpha/lib_protocol/src/script_expr_hash.ml
@@ -0,0 +1,20 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2018.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+let script_expr_hash = "\013\044\064\027" (* expr(54) *)
+
+include Blake2B.Make(Base58)(struct
+    let name = "script_expr"
+    let title = "A script expression ID"
+    let b58check_prefix = script_expr_hash
+    let size = None
+  end)
+
+let () =
+  Base58.check_encoded_prefix b58check_encoding "expr" 54
diff --git a/src/proto_alpha/lib_protocol/src/script_ir_translator.ml b/src/proto_alpha/lib_protocol/src/script_ir_translator.ml
index b5943384f..e6cef1123 100644
--- a/src/proto_alpha/lib_protocol/src/script_ir_translator.ml
+++ b/src/proto_alpha/lib_protocol/src/script_ir_translator.ml
@@ -2130,7 +2130,7 @@ let typecheck_data
 let hash_data typ data =
   let unparsed = strip_annotations @@ unparse_data typ data in
   let bytes = Data_encoding.Binary.to_bytes expr_encoding (Micheline.strip_locations unparsed) in
-  Tezos_hash.Script_expr_hash.(hash_bytes [ bytes ] |> to_b58check)
+  Script_expr_hash.(hash_bytes [ bytes ] |> to_b58check)
 
 (* ---------------- Big map -------------------------------------------------*)
 
diff --git a/src/proto_alpha/lib_protocol/src/seed_repr.ml b/src/proto_alpha/lib_protocol/src/seed_repr.ml
index 4d49237f3..7f914b827 100644
--- a/src/proto_alpha/lib_protocol/src/seed_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/seed_repr.ml
@@ -9,8 +9,6 @@
 
 (* Tezos Protocol Implementation - Random number generation *)
 
-open Tezos_hash
-
 type seed = B of State_hash.t
 type t = T of State_hash.t
 type sequence = S of State_hash.t
diff --git a/src/proto_alpha/lib_protocol/src/seed_repr.mli b/src/proto_alpha/lib_protocol/src/seed_repr.mli
index 06f04f42c..994987c82 100644
--- a/src/proto_alpha/lib_protocol/src/seed_repr.mli
+++ b/src/proto_alpha/lib_protocol/src/seed_repr.mli
@@ -7,8 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-open Tezos_hash
-
 (** Tezos Protocol Implementation - Random number generation
 
     This is not expected to be a good cryptographic random number
diff --git a/src/proto_alpha/lib_protocol/src/state_hash.ml b/src/proto_alpha/lib_protocol/src/state_hash.ml
new file mode 100644
index 000000000..91790ace5
--- /dev/null
+++ b/src/proto_alpha/lib_protocol/src/state_hash.ml
@@ -0,0 +1,21 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2018.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+let random_state_hash = "\076\064\204" (* rng(53): never used... *)
+
+include Blake2B.Make(Base58)(struct
+    let name = "random"
+    let title = "A random generation state"
+    let b58check_prefix = random_state_hash
+    let size = None
+  end)
+
+let () =
+  Base58.check_encoded_prefix b58check_encoding "rng" 53
+
diff --git a/src/proto_alpha/lib_protocol/src/storage.ml b/src/proto_alpha/lib_protocol/src/storage.ml
index cd1c822dd..b5608b222 100644
--- a/src/proto_alpha/lib_protocol/src/storage.ml
+++ b/src/proto_alpha/lib_protocol/src/storage.ml
@@ -7,7 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-open Tezos_hash
 open Storage_functors
 
 module Int32 = struct
diff --git a/src/proto_alpha/lib_protocol/src/storage.mli b/src/proto_alpha/lib_protocol/src/storage.mli
index 203b08f07..843c74818 100644
--- a/src/proto_alpha/lib_protocol/src/storage.mli
+++ b/src/proto_alpha/lib_protocol/src/storage.mli
@@ -209,7 +209,7 @@ module Seed : sig
 
   type nonce_status =
     | Unrevealed of {
-        nonce_hash: Tezos_hash.Nonce_hash.t ;
+        nonce_hash: Nonce_hash.t ;
         delegate_to_reward: Ed25519.Public_key_hash.t ;
         reward_amount: Tez_repr.t ;
       }
diff --git a/src/proto_alpha/lib_protocol/src/tezos_hash.ml b/src/proto_alpha/lib_protocol/src/tezos_hash.ml
deleted file mode 100644
index 9f4d46b2b..000000000
--- a/src/proto_alpha/lib_protocol/src/tezos_hash.ml
+++ /dev/null
@@ -1,54 +0,0 @@
-(**************************************************************************)
-(*                                                                        *)
-(*    Copyright (c) 2014 - 2018.                                          *)
-(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
-(*                                                                        *)
-(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
-(*                                                                        *)
-(**************************************************************************)
-
-module Prefix = struct
-
-  (* 20 *)
-  let contract_hash = "\003\099\029" (* TZ(36) *)
-
-  (* 32 *)
-  let nonce_hash = "\069\220\169" (* nce(53) *)
-  let script_expr_hash = "\013\044\064\027" (* expr(54) *)
-  let random_state_hash = "\076\064\204" (* rng(53): never used... *)
-
-end
-
-module State_hash = Blake2B.Make(Base58)(struct
-    let name = "random"
-    let title = "A random generation state"
-    let b58check_prefix = Prefix.random_state_hash
-    let size = None
-  end)
-
-module Nonce_hash = Blake2B.Make(Base58)(struct
-    let name = "cycle_nonce"
-    let title = "A nonce hash"
-    let b58check_prefix = Prefix.nonce_hash
-    let size = None
-  end)
-
-module Script_expr_hash = Blake2B.Make(Base58)(struct
-    let name = "script_expr"
-    let title = "A script expression ID"
-    let b58check_prefix = Prefix.script_expr_hash
-    let size = None
-  end)
-
-module Contract_hash = Blake2B.Make(Base58)(struct
-    let name = "Contract_hash"
-    let title = "A contract ID"
-    let b58check_prefix = Prefix.contract_hash
-    let size = Some 20
-  end)
-
-let () =
-  Base58.check_encoded_prefix Contract_hash.b58check_encoding "TZ1" 36 ;
-  Base58.check_encoded_prefix Script_expr_hash.b58check_encoding "expr" 54 ;
-  Base58.check_encoded_prefix Nonce_hash.b58check_encoding "nce" 53 ;
-  Base58.check_encoded_prefix State_hash.b58check_encoding "rng" 53