From 077b4d25200962b32699a1a1bff52bd7c36aefda Mon Sep 17 00:00:00 2001
From: swrup <swrup@protonmail.com>
Date: Fri, 13 Feb 2026 23:18:43 +0100
Subject: [PATCH]

---
 src/crypto.ml  | 44 ++++++++++++++++++++++++++++++++++++++++++++
 test/crypto.ml |  8 ++++++++
 2 files changed, 52 insertions(+)

diff --git a/src/crypto.ml b/src/crypto.ml
index 8b6ab805..35e996e0 100644
--- a/src/crypto.ml
+++ b/src/crypto.ml
@@ -1,5 +1,49 @@
 open Syntax
 
+module Gcrypt_sexpr = struct
+  open Angstrom
+
+  type expr =
+    | List of string * expr list
+    | Leaf of string * Z.t
+
+  let rec pp ppf t =
+    match t with
+    | List (k, l) -> Fmt.pf ppf "%s: @[ %a @]@." k (Fmt.list pp) l
+    | Leaf (k, z) ->
+        Fmt.pf ppf "%s: %S@." k (Mirage_crypto_pk.Z_extra.to_octets_be z)
+
+  let str =
+    take_while (( <> ) ':') <* char ':' >>= fun s ->
+    Fmt.epr "@. --- s: %S@." s;
+    let len = int_of_string s in
+    Fmt.epr "@. --- len: %d@." len;
+    take len
+
+  let leaf =
+    lift2
+      (fun k v -> Leaf (k, v))
+      str
+      (str >>| Mirage_crypto_pk.Z_extra.of_octets_be)
+
+  let ws = many (char ' ' <|> char '\n')
+
+  let sexpr =
+    fix (fun expr ->
+        char '('
+        *> ws
+        *> lift2 (fun k l -> List (k, l)) (str <* ws) (many1 expr)
+        <|> leaf
+        <* ws
+        <* char ')'
+        <* ws)
+
+  let parse s =
+    match parse_string ~consume:All sexpr s with
+    | Error msg -> Fmt.failwith "parse error `%s`" msg
+    | Ok v -> v
+end
+
 module Binary_format_rsa = struct
   (* RSA public key binary format
        https://www.gnupg.org/documentation/manuals/gcrypt/MPI-formats.html
diff --git a/test/crypto.ml b/test/crypto.ml
index 3facd609..4c2b1e68 100644
--- a/test/crypto.ml
+++ b/test/crypto.ml
@@ -99,6 +99,9 @@ let () =
   let message_hash =
     "XKQMJ4CNTXBFE1V2WR6JS063J7PZQE4XMB5JH3RS5X0THQ1JQSQ69Y7KDBC9TYRJEZH48MEPY2SF4QHQ4VHXC0YQX5935MQEGP0AX6R"
   in
+  let rsa_private_key =
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
+  in
   let rsa_public_key =
     "040000YRN1NVJ68RS6RJF52PGRCQG19ZKWQPSTJX2G7ZDCKSZFE2VW3HHA81YF5C639JHJF5TX8YTEE2FW2WQCG1PTKNBSPPJEJGA032CN3E8QZ27VWY0K6JFT8ZSYWRH2SKDMXW56A4QKY46JJBWJ6T0ZRVBW6S1HTHXVE2RW8MXRW5T801077MDY13N5F8Z1JZVKBJ06TK3S0YPEDBXK0VEHRHEQJ5X5XYKR4KQTFAZNBMKXY8836VCHBXTK4YNX6AJ1CK29SMJH3Z3QRM16A2TNQGFR0HSMV446BF7FMT2E379ZAT5ST4G3BM2NWZYW545S2SW5MG5S6M88XZZ7SKFD48YVXNZ205GGSEYJPVBMR76WG4ZG30WBCPC1N54XE12RMAG81D8C09WG22PKGGDHYXX68N04002"
   in
@@ -117,4 +120,9 @@ let () =
   let s = rsa_blind pub ~bks ~msg |> encode in
   assert (s = blinded_message);
 
+  let priv = decode rsa_private_key in
+  Fmt.pr "%s@." priv;
+  let priv = Gcrypt_sexpr.parse priv in
+  Fmt.pr "%a@." Gcrypt_sexpr.pp priv;
+
   ()