diff --git a/src/lib_crypto/signature.ml b/src/lib_crypto/signature.ml
index df61310038..15d633c3b2 100644
--- a/src/lib_crypto/signature.ml
+++ b/src/lib_crypto/signature.ml
@@ -634,7 +634,7 @@ let pp_watermark ppf =
         "Custom: 0x%s"
         (try String.sub hexed 0 10 ^ "..." with Invalid_argument _ -> hexed)
 
-let sign ?watermark secret_key message =
+let _sign ?watermark secret_key message =
   let watermark = Option.map bytes_of_watermark watermark in
   match secret_key with
   | Secret_key.Ed25519 sk -> of_ed25519 (Ed25519.sign ?watermark sk message)
@@ -664,6 +664,25 @@ let check ?watermark public_key signature message =
       P256.check ?watermark pk signature message
   | _ -> false
 
+let fake_sign pk_bytes msg =
+  let half = size / 2 in
+  let tmp = Bytes.init size (fun _ -> '0') in
+  let all_or_half buf = Stdlib.min (Bytes.length buf) half in
+  Bytes.blit pk_bytes 0 tmp 0 (all_or_half pk_bytes) ;
+  Bytes.blit msg 0 tmp half (all_or_half msg) ;
+  of_bytes_exn tmp
+
+let fake_check ?watermark pk signature msg =
+  let pk_bytes = Data_encoding.Binary.to_bytes_exn Public_key.encoding pk in
+  if equal signature (fake_sign pk_bytes msg) then true
+  else check ?watermark pk signature msg
+
+let sign ?watermark:_ sk msg =
+  let pk_bytes = Data_encoding.Binary.to_bytes_exn Secret_key.encoding sk in
+  fake_sign pk_bytes msg
+
+let check = fake_check
+
 (* The following cache is a hack to work around a quadratic algorithm
    in Tezos Mainnet protocols up to Edo. *)
 
@@ -735,7 +754,17 @@ let concat msg signature = Bytes.cat msg (to_bytes signature)
 
 type algo = Ed25519 | Secp256k1 | P256
 
-let generate_key ?(algo = Ed25519) ?seed () =
+let fake_generate_key (pkh, pk, _) =
+  let sk_of_pk (pk : public_key) : secret_key =
+    let pk_b = Data_encoding.Binary.to_bytes_exn Public_key.encoding pk in
+    let sk_b = Bytes.sub pk_b 0 33 in
+    let sk = Data_encoding.Binary.of_bytes_exn Secret_key.encoding sk_b in
+    sk
+  in
+  let fake_sk = sk_of_pk pk in
+  (pkh, pk, fake_sk)
+
+let original_generate_key ?(algo = Ed25519) ?seed () =
   match algo with
   | Ed25519 ->
       let (pkh, pk, sk) = Ed25519.generate_key ?seed () in
@@ -749,6 +778,12 @@ let generate_key ?(algo = Ed25519) ?seed () =
       let (pkh, pk, sk) = P256.generate_key ?seed () in
       (Public_key_hash.P256 pkh, Public_key.P256 pk, Secret_key.P256 sk)
 
+let generate_key ?(algo = Ed25519) ?seed () =
+  (* We keep the original keys generation to stay as close as possible of the
+     initial performences. *)
+  let true_keys = original_generate_key ~algo ?seed () in
+  fake_generate_key true_keys
+
 let deterministic_nonce sk msg =
   match sk with
   | Secret_key.Ed25519 sk -> Ed25519.deterministic_nonce sk msg