From 30fae43da3fc566c3595084941e01af1b6634925 Mon Sep 17 00:00:00 2001
From: swrup <swrup@protonmail.com>
Date: Tue, 24 Feb 2026 21:21:44 +0100
Subject: [PATCH]

---
 src/crypto.ml       | 11 +----------
 src/fdh_rsa.ml      | 20 +++++++++++++-------
 src/secmod_rsa.ml   |  5 +++--
 test/test_crypto.ml |  2 +-
 4 files changed, 18 insertions(+), 20 deletions(-)

diff --git a/src/crypto.ml b/src/crypto.ml
index bc42c580..2f42ae72 100644
--- a/src/crypto.ml
+++ b/src/crypto.ml
@@ -248,18 +248,9 @@ module RsaPrivateKey = struct
     Jsont.of_of_string ~kind:"RsaPrivateKey" of_b32 ~enc:to_b32
 end
 
-module RsaSignature : sig
-  type t
-
-  val jsont : t Jsont.t
-  val sign : key:RsaPrivateKey.t -> string -> t
-end = struct
+module RsaSignature = struct
   type t = string
 
-  (* TODO crypto
-     this is a placeholder signature algorithm *)
-  let sign ~key s = Mirage_crypto_pk.Rsa.PKCS1.sig_encode ~key s
-
   let jsont =
     let of_b32 s = B32.decode s in
     let to_b32 t = B32.encode t in
diff --git a/src/fdh_rsa.ml b/src/fdh_rsa.ml
index 692ecd30..13bbc439 100644
--- a/src/fdh_rsa.ml
+++ b/src/fdh_rsa.ml
@@ -1,4 +1,4 @@
-(* WIP
+(* TODO WIP fdh-rsa
    full-domain-hash RSA
    based on libgnunetutil crypto_rsa.c
 
@@ -56,7 +56,7 @@ let rsa_blinding_key_derive (pub : RsaPublicKey.t) bks =
   let r = Kdf.kdf_mod_n ~n:pub.n ~xts ~ikm:bks ~ctx in
   gcd_validate r pub.n; r
 
-let rsa_blind pub ~bks ~msg =
+let rsa_blind pub ~bks msg =
   let data = rsa_full_domain_hash pub msg in
   let bkey = rsa_blinding_key_derive pub bks in
   (* can we just use [powm] here instead? *)
@@ -65,11 +65,11 @@ let rsa_blind pub ~bks ~msg =
   Z_extra.to_octets_be data_r_e
 
 (* decrypt <=> sign *)
-let rsa_sign_blinded priv ~bmsg =
+let rsa_sign_blinded priv bmsg =
   Mirage_crypto_pk.Rsa.decrypt ~crt_hardening:true ~key:priv bmsg
 
-let rsa_unblind pub ~bks ~sig_ =
-  let data = Z_extra.of_octets_be sig_ in
+let rsa_unblind pub ~bks bsig =
+  let data = Z_extra.of_octets_be bsig in
   let bkey = rsa_blinding_key_derive pub bks in
   let r_inv =
     try Z.invert bkey pub.n
@@ -80,10 +80,16 @@ let rsa_unblind pub ~bks ~sig_ =
   let data = Z.rem (Z.mul data r_inv) pub.n in
   Z_extra.to_octets_be data
 
-(* TODO crypto
+let sign ~priv ~pub ~bks ~msg =
+  let bmsg = rsa_blind pub ~bks msg in
+  let bsig = rsa_sign_blinded priv bmsg in
+  let sig_ = rsa_unblind pub ~bks bsig in
+  sig_
+
+(* TODO fdh-rsa
    look into mirage-crypto for this
    at least use Eqaf for constant time string compare *)
-let rsa_verify pub ~msg ~sig_ =
+let verify pub ~msg ~sig_ =
   let msg_fdh = rsa_full_domain_hash pub msg in
   let s1 = Z_extra.to_octets_be msg_fdh in
   let s2 = Mirage_crypto_pk.Rsa.encrypt ~key:pub sig_ in
diff --git a/src/secmod_rsa.ml b/src/secmod_rsa.ml
index 10bec6b7..c8c17deb 100644
--- a/src/secmod_rsa.ml
+++ b/src/secmod_rsa.ml
@@ -257,9 +257,10 @@ module Make () = struct
   let sm_pub = t.sm_pub
   let sign_secmod s = EddsaSignature.sign ~key:t.sm_key_priv s
 
-  let sign h_pub s =
+  let sign h_pub msg =
     let+ k = find h_pub in
-    let data = RsaSignature.sign ~key:k.priv s in
+    let bks = "deadbeaf" in
+    let data = Fdh_rsa.sign ~priv:k.priv ~pub:k.pub ~bks ~msg in
     data
 
   let revoke h_pub =
diff --git a/test/test_crypto.ml b/test/test_crypto.ml
index d146a633..28c1e780 100644
--- a/test/test_crypto.ml
+++ b/test/test_crypto.ml
@@ -104,7 +104,7 @@ let () =
   in
   let bks = blinding_key_secret |> decode in
   let msg = decode message_hash in
-  let bmsg = Fdh_rsa.rsa_blind pub ~bks ~msg in
+  let bmsg = Fdh_rsa.rsa_blind pub ~bks msg in
   assert (encode bmsg = blinded_message);
 
   ()