diff --git a/src/bin_sig.ml b/src/bin_sig.ml
index 1c95cdcc..fda9762a 100644
--- a/src/bin_sig.ml
+++ b/src/bin_sig.ml
@@ -77,13 +77,17 @@ module MK (R : sig
 
   val bin : r Bin.t
 end) : sig
+  open Crypto
+
   type r = R.r
   type t
 
-  val sign : key:Crypto.EddsaPrivateKey.t -> r -> t
+  val signf : r -> key:EddsaPrivateKey.t -> t
+  val sign : key:EddsaPrivateKey.t -> r -> t
+  val sign' : r -> (string -> EddsaSignature.t) -> t r -> (r -> string) -> t
 
   (* Ok () on verification success *)
-  val verify : key:Crypto.EddsaPublicKey.t -> t -> r -> (unit, string) result
+  val verify : key:EddsaPublicKey.t -> t -> r -> (unit, string) result
   val jsont : t Jsont.t
   val caqti : t Caqti_type.t
 end = struct
@@ -93,7 +97,9 @@ end = struct
   type t = EddsaSignature.t
 
   let bin = R.bin
+  let signf = EddsaSignature.mk_signf (Bin.to_string bin)
   let sign ~key r = EddsaSignature.sign ~key (Bin.to_string bin r)
+  let sign' r signf = signf (Bin.to_string bin r)
 
   let verify ~key t r =
     let b = EddsaSignature.verify ~key t ~msg:(Bin.to_string bin r) in
diff --git a/src/crypto.ml b/src/crypto.ml
index 6abf3849..bb3a4466 100644
--- a/src/crypto.ml
+++ b/src/crypto.ml
@@ -74,6 +74,7 @@ end
 module EddsaSignature : sig
   type t
 
+  val mk_signf : ('r -> string) -> 'r -> key:EddsaPrivateKey.t -> t
   val sign : key:EddsaPrivateKey.t -> string -> t
   val verify : key:EddsaPublicKey.t -> t -> msg:string -> bool
   val to_octets : t -> string
@@ -88,6 +89,9 @@ end = struct
      binary-encoded objects with just the R and S values *)
   type t = string
 
+  let mk_signf to_string =
+   fun r ~key -> Mirage_crypto_ec.Ed25519.sign ~key (to_string r)
+
   (* mirage_crypto: "The result is the concatenation of r and s, as specified in RFC 8032." *)
   let sign ~key s = Mirage_crypto_ec.Ed25519.sign ~key s
   let verify ~key s ~msg = Mirage_crypto_ec.Ed25519.verify ~key s ~msg