core/secp256k1_zkp: refactor API into a Context class

In order to prevent frequent memory allocations, the user can create a single
Context object and re-use it between subsequent cryptographic operations.

core/embed/extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h

@@ -37,79 +37,115 @@ void secp256k1_default_error_callback_fn(const char *str, void *data) {
   return;
 }
 
-static secp256k1_context *secp256k1_ctx = NULL;
-static void *secp256k1_ctx_buf = NULL;
-static size_t secp256k1_ctx_size = 0;
-
-static const secp256k1_context *mod_trezorcrypto_secp256k1_context_create(
-    void) {
-  if (secp256k1_ctx == NULL) {
-    secp256k1_ctx_size = secp256k1_context_preallocated_size(
-        SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
-    secp256k1_ctx_buf = m_new_maybe(uint8_t, secp256k1_ctx_size);
-    if (!secp256k1_ctx_buf) {
-      mp_raise_ValueError("secp256k1_zkp context is too large");
-    }
-    secp256k1_ctx = secp256k1_context_preallocated_create(
-        secp256k1_ctx_buf, SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
-
-    uint8_t rand[32];
-    random_buffer(rand, 32);
-    int ret = secp256k1_context_randomize(secp256k1_ctx, rand);
-    if (ret != 1) {
-      mp_raise_msg(&mp_type_RuntimeError, "secp256k1_context_randomize failed");
-    }
-  }
-  return secp256k1_ctx;
-}
-
-STATIC void mod_trezorcrypto_secp256k1_context_delete(void) {
-  secp256k1_context_preallocated_destroy(secp256k1_ctx);
-  m_del(uint8_t, secp256k1_ctx_buf, secp256k1_ctx_size);
-  secp256k1_ctx_buf = NULL;
-  secp256k1_ctx = NULL;
-}
-
 /// package: trezorcrypto.secp256k1_zkp
 
-/// def generate_secret() -> bytes:
+/// class Context:
+///     """
+///     Owns a secp256k1 context.
+///     Can be allocated once and re-used between subsequent operations.
+///     """
+///
+typedef struct _mp_obj_secp256k1_context_t {
+  mp_obj_base_t base;
+  secp256k1_context *secp256k1_ctx;
+  size_t secp256k1_ctx_size;
+  uint8_t secp256k1_ctx_buf[0];  // to be allocate via m_new_obj_var_maybe().
+} mp_obj_secp256k1_context_t;
+
+/// def __init__(self):
+///     """
+///     Allocate and initialize secp256k1_context.
+///     """
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_make_new(
+    const mp_obj_type_t *type, size_t n_args, size_t n_kw,
+    const mp_obj_t *args) {
+  mp_arg_check_num(n_args, n_kw, 0, 0, false);
+
+  const size_t secp256k1_ctx_size = secp256k1_context_preallocated_size(
+      SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+
+  mp_obj_secp256k1_context_t *o = m_new_obj_var_maybe(
+      mp_obj_secp256k1_context_t, uint8_t, secp256k1_ctx_size);
+  if (!o) {
+    mp_raise_ValueError("secp256k1_zkp context is too large");
+  }
+  o->base.type = type;
+  o->secp256k1_ctx_size = secp256k1_ctx_size;
+  o->secp256k1_ctx = secp256k1_context_preallocated_create(
+      o->secp256k1_ctx_buf, SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+
+  uint8_t rand[32] = {0};
+  random_buffer(rand, 32);
+  int ret = secp256k1_context_randomize(o->secp256k1_ctx, rand);
+  if (ret != 1) {
+    mp_raise_msg(&mp_type_RuntimeError, "secp256k1_context_randomize failed");
+  }
+
+  return MP_OBJ_FROM_PTR(o);
+}
+
+/// def __del__(self):
+///     """
+///     Destructor.
+///     """
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_context___del__(mp_obj_t self) {
+  mp_obj_secp256k1_context_t *o = MP_OBJ_TO_PTR(self);
+  secp256k1_context_preallocated_destroy(o->secp256k1_ctx);
+  memzero(o->secp256k1_ctx_buf, o->secp256k1_ctx_size);
+  return mp_const_none;
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_secp256k1_context___del___obj,
+                                 mod_trezorcrypto_secp256k1_context___del__);
+
+/// def size(self):
+///     """
+///     Return the size in bytes of the internal secp256k1_ctx_buf buffer.
+///     """
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_size(mp_obj_t self) {
+  mp_obj_secp256k1_context_t *o = MP_OBJ_TO_PTR(self);
+  return mp_obj_new_int_from_uint(o->secp256k1_ctx_size);
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_secp256k1_context_size_obj,
+                                 mod_trezorcrypto_secp256k1_context_size);
+
+static const secp256k1_context *mod_trezorcrypto_get_secp256k1_context(
+    mp_obj_t self) {
+  mp_obj_secp256k1_context_t *o = MP_OBJ_TO_PTR(self);
+  return o->secp256k1_ctx;
+}
+
+/// def generate_secret(self) -> bytes:
 ///     """
 ///     Generate secret key.
 ///     """
-STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_generate_secret() {
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_generate_secret(mp_obj_t self) {
-  uint8_t out[32];
+  const secp256k1_context *ctx = mod_trezorcrypto_get_secp256k1_context(self);
+  uint8_t out[32] = {0};
   for (;;) {
     random_buffer(out, 32);
     // check whether secret > 0 && secret < curve_order
-    if (0 == memcmp(out,
+    if (secp256k1_ec_seckey_verify(ctx, out) == 1) {
-                    "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+      break;
-                    "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+    }
-                    "\x00\x00\x00\x00\x00\x00",
-                    32))
-      continue;
-    if (0 <= memcmp(out,
-                    "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"
-                    "\xFF\xFF\xFE\xBA\xAE\xDC\xE6\xAF\x48\xA0\x3B\xBF\xD2"
-                    "\x5E\x8C\xD0\x36\x41\x41",
-                    32))
-      continue;
-    break;
   }
   return mp_obj_new_bytes(out, sizeof(out));
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_0(
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(
     mod_trezorcrypto_secp256k1_zkp_generate_secret_obj,
     mod_trezorcrypto_secp256k1_zkp_generate_secret);
 
-/// def publickey(secret_key: bytes, compressed: bool = True) -> bytes:
+/// def publickey(self, secret_key: bytes, compressed: bool = True) -> bytes:
 ///     """
 ///     Computes public key from secret key.
 ///     """
-STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_publickey(size_t n_args,
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_publickey(
-                                                         const mp_obj_t *args) {
+    size_t n_args, const mp_obj_t *args) {
-  const secp256k1_context *ctx = mod_trezorcrypto_secp256k1_context_create();
+  const secp256k1_context *ctx =
+      mod_trezorcrypto_get_secp256k1_context(args[0]);
   mp_buffer_info_t sk;
-  mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
+  mp_get_buffer_raise(args[1], &sk, MP_BUFFER_READ);
   secp256k1_pubkey pk;
   if (sk.len != 32) {
     mp_raise_ValueError("Invalid length of secret key");
@@ -118,32 +154,32 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_publickey(size_t n_args,
     mp_raise_ValueError("Invalid secret key");
   }
 
-  bool compressed = n_args < 2 || args[1] == mp_const_true;
+  bool compressed = n_args < 3 || args[2] == mp_const_true;
   uint8_t out[65];
   size_t outlen = sizeof(out);
   secp256k1_ec_pubkey_serialize(
       ctx, out, &outlen, &pk,
       compressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
-  mod_trezorcrypto_secp256k1_context_delete();
   return mp_obj_new_bytes(out, outlen);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
-    mod_trezorcrypto_secp256k1_zkp_publickey_obj, 1, 2,
+    mod_trezorcrypto_secp256k1_context_publickey_obj, 2, 3,
-    mod_trezorcrypto_secp256k1_zkp_publickey);
+    mod_trezorcrypto_secp256k1_context_publickey);
 
 /// def sign(
-///     secret_key: bytes, digest: bytes, compressed: bool = True
+///     self, secret_key: bytes, digest: bytes, compressed: bool = True
 /// ) -> bytes:
 ///     """
 ///     Uses secret key to produce the signature of the digest.
 ///     """
-STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_sign(size_t n_args,
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_sign(size_t n_args,
-                                                    const mp_obj_t *args) {
+                                                        const mp_obj_t *args) {
-  const secp256k1_context *ctx = mod_trezorcrypto_secp256k1_context_create();
+  const secp256k1_context *ctx =
+      mod_trezorcrypto_get_secp256k1_context(args[0]);
   mp_buffer_info_t sk, dig;
-  mp_get_buffer_raise(args[0], &sk, MP_BUFFER_READ);
+  mp_get_buffer_raise(args[1], &sk, MP_BUFFER_READ);
-  mp_get_buffer_raise(args[1], &dig, MP_BUFFER_READ);
+  mp_get_buffer_raise(args[2], &dig, MP_BUFFER_READ);
-  bool compressed = n_args < 3 || args[2] == mp_const_true;
+  bool compressed = n_args < 4 || args[3] == mp_const_true;
   if (sk.len != 32) {
     mp_raise_ValueError("Invalid length of secret key");
   }
@@ -159,27 +195,28 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_sign(size_t n_args,
   }
   secp256k1_ecdsa_recoverable_signature_serialize_compact(ctx, &out[1], &pby,
                                                           &sig);
-  mod_trezorcrypto_secp256k1_context_delete();
   out[0] = 27 + pby + compressed * 4;
   return mp_obj_new_bytes(out, sizeof(out));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
-    mod_trezorcrypto_secp256k1_zkp_sign_obj, 2, 3,
+    mod_trezorcrypto_secp256k1_context_sign_obj, 3, 4,
-    mod_trezorcrypto_secp256k1_zkp_sign);
+    mod_trezorcrypto_secp256k1_context_sign);
 
-/// def verify(public_key: bytes, signature: bytes, digest: bytes) -> bool:
+/// def verify(
+///     self, public_key: bytes, signature: bytes, digest: bytes
+/// ) -> bool:
 ///     """
 ///     Uses public key to verify the signature of the digest.
 ///     Returns True on success.
 ///     """
-STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_verify(mp_obj_t public_key,
+STATIC mp_obj_t
-                                                      mp_obj_t signature,
+mod_trezorcrypto_secp256k1_context_verify(size_t n_args, const mp_obj_t *args) {
-                                                      mp_obj_t digest) {
+  const secp256k1_context *ctx =
-  const secp256k1_context *ctx = mod_trezorcrypto_secp256k1_context_create();
+      mod_trezorcrypto_get_secp256k1_context(args[0]);
   mp_buffer_info_t pk, sig, dig;
-  mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
+  mp_get_buffer_raise(args[1], &pk, MP_BUFFER_READ);
-  mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
+  mp_get_buffer_raise(args[2], &sig, MP_BUFFER_READ);
-  mp_get_buffer_raise(digest, &dig, MP_BUFFER_READ);
+  mp_get_buffer_raise(args[3], &dig, MP_BUFFER_READ);
   if (pk.len != 33 && pk.len != 65) {
     return mp_const_false;
   }
@@ -202,20 +239,20 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_verify(mp_obj_t public_key,
   }
   bool ret = (1 == secp256k1_ecdsa_verify(ctx, &ec_sig,
                                           (const uint8_t *)dig.buf, &ec_pk));
-  mod_trezorcrypto_secp256k1_context_delete();
   return mp_obj_new_bool(ret);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_3(mod_trezorcrypto_secp256k1_zkp_verify_obj,
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(
-                                 mod_trezorcrypto_secp256k1_zkp_verify);
+    mod_trezorcrypto_secp256k1_context_verify_obj, 4, 4,
+    mod_trezorcrypto_secp256k1_context_verify);
 
-/// def verify_recover(signature: bytes, digest: bytes) -> bytes:
+/// def verify_recover(self, signature: bytes, digest: bytes) -> bytes:
 ///     """
 ///     Uses signature of the digest to verify the digest and recover the public
 ///     key. Returns public key on success, None if the signature is invalid.
 ///     """
-STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_verify_recover(
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_verify_recover(
-    mp_obj_t signature, mp_obj_t digest) {
+    mp_obj_t self, mp_obj_t signature, mp_obj_t digest) {
-  const secp256k1_context *ctx = mod_trezorcrypto_secp256k1_context_create();
+  const secp256k1_context *ctx = mod_trezorcrypto_get_secp256k1_context(self);
   mp_buffer_info_t sig, dig;
   mp_get_buffer_raise(signature, &sig, MP_BUFFER_READ);
   mp_get_buffer_raise(digest, &dig, MP_BUFFER_READ);
@@ -246,12 +283,11 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_verify_recover(
   secp256k1_ec_pubkey_serialize(
       ctx, out, &pklen, &pk,
       compressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
-  mod_trezorcrypto_secp256k1_context_delete();
   return mp_obj_new_bytes(out, pklen);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(
-    mod_trezorcrypto_secp256k1_zkp_verify_recover_obj,
+    mod_trezorcrypto_secp256k1_context_verify_recover_obj,
-    mod_trezorcrypto_secp256k1_zkp_verify_recover);
+    mod_trezorcrypto_secp256k1_context_verify_recover);
 
 static int secp256k1_ecdh_hash_passthrough(uint8_t *output, const uint8_t *x,
                                            const uint8_t *y, void *data) {
@@ -262,14 +298,14 @@ static int secp256k1_ecdh_hash_passthrough(uint8_t *output, const uint8_t *x,
   return 1;
 }
 
-/// def multiply(secret_key: bytes, public_key: bytes) -> bytes:
+/// def multiply(self, secret_key: bytes, public_key: bytes) -> bytes:
 ///     """
 ///     Multiplies point defined by public_key with scalar defined by
 ///     secret_key. Useful for ECDH.
 ///     """
-STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_multiply(mp_obj_t secret_key,
+STATIC mp_obj_t mod_trezorcrypto_secp256k1_context_multiply(
-                                                        mp_obj_t public_key) {
+    mp_obj_t self, mp_obj_t secret_key, mp_obj_t public_key) {
-  const secp256k1_context *ctx = mod_trezorcrypto_secp256k1_context_create();
+  const secp256k1_context *ctx = mod_trezorcrypto_get_secp256k1_context(self);
   mp_buffer_info_t sk, pk;
   mp_get_buffer_raise(secret_key, &sk, MP_BUFFER_READ);
   mp_get_buffer_raise(public_key, &pk, MP_BUFFER_READ);
@@ -289,27 +325,50 @@ STATIC mp_obj_t mod_trezorcrypto_secp256k1_zkp_multiply(mp_obj_t secret_key,
                       secp256k1_ecdh_hash_passthrough, NULL)) {
     mp_raise_ValueError("Multiply failed");
   }
-  mod_trezorcrypto_secp256k1_context_delete();
   return mp_obj_new_bytes(out, sizeof(out));
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_secp256k1_zkp_multiply_obj,
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(
-                                 mod_trezorcrypto_secp256k1_zkp_multiply);
+    mod_trezorcrypto_secp256k1_context_multiply_obj,
+    mod_trezorcrypto_secp256k1_context_multiply);
+
+//////////////////////////////////////////////////////////////////////////////
+
+STATIC const mp_rom_map_elem_t
+    mod_trezorcrypto_secp256k1_context_locals_dict_table[] = {
+        {MP_ROM_QSTR(MP_QSTR___del__),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context___del___obj)},
+        {MP_ROM_QSTR(MP_QSTR_size),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context_size_obj)},
+        {MP_ROM_QSTR(MP_QSTR_generate_secret),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_zkp_generate_secret_obj)},
+        {MP_ROM_QSTR(MP_QSTR_publickey),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context_publickey_obj)},
+        {MP_ROM_QSTR(MP_QSTR_sign),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context_sign_obj)},
+        {MP_ROM_QSTR(MP_QSTR_verify),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context_verify_obj)},
+        {MP_ROM_QSTR(MP_QSTR_verify_recover),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context_verify_recover_obj)},
+        {MP_ROM_QSTR(MP_QSTR_multiply),
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context_multiply_obj)},
+};
+
+STATIC MP_DEFINE_CONST_DICT(
+    mod_trezorcrypto_secp256k1_context_locals_dict,
+    mod_trezorcrypto_secp256k1_context_locals_dict_table);
+
+STATIC const mp_obj_type_t mod_trezorcrypto_secp256k1_context_type = {
+    {&mp_type_type},
+    .name = MP_QSTR_Context,
+    .make_new = mod_trezorcrypto_secp256k1_context_make_new,
+    .locals_dict = (void *)&mod_trezorcrypto_secp256k1_context_locals_dict,
+};
 
 STATIC const mp_rom_map_elem_t
     mod_trezorcrypto_secp256k1_zkp_globals_table[] = {
         {MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_secp256k1_zkp)},
-        {MP_ROM_QSTR(MP_QSTR_generate_secret),
+        {MP_ROM_QSTR(MP_QSTR_Context),
-         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_zkp_generate_secret_obj)},
+         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_context_type)},
-        {MP_ROM_QSTR(MP_QSTR_publickey),
-         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_zkp_publickey_obj)},
-        {MP_ROM_QSTR(MP_QSTR_sign),
-         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_zkp_sign_obj)},
-        {MP_ROM_QSTR(MP_QSTR_verify),
-         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_zkp_verify_obj)},
-        {MP_ROM_QSTR(MP_QSTR_verify_recover),
-         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_zkp_verify_recover_obj)},
-        {MP_ROM_QSTR(MP_QSTR_multiply),
-         MP_ROM_PTR(&mod_trezorcrypto_secp256k1_zkp_multiply_obj)},
 };
 STATIC MP_DEFINE_CONST_DICT(mod_trezorcrypto_secp256k1_zkp_globals,
                             mod_trezorcrypto_secp256k1_zkp_globals_table);

core/mocks/generated/trezorcrypto/secp256k1_zkp.py

@@ -2,47 +2,60 @@ from typing import *
 
 
 # extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
-def generate_secret() -> bytes:
+class Context:
     """
-    Generate secret key.
+    Owns a secp256k1 context.
+    Can be allocated once and re-used between subsequent operations.
     """
 
+    def __init__(self):
+        """
+        Allocate and initialize secp256k1_context.
+        """
 
-# extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
+    def __del__(self):
-def publickey(secret_key: bytes, compressed: bool = True) -> bytes:
+        """
-    """
+        Destructor.
-    Computes public key from secret key.
+        """
-    """
 
+    def size(self):
+        """
+        Return the size in bytes of the internal secp256k1_ctx_buf buffer.
+        """
 
-# extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
+    def generate_secret(self) -> bytes:
-def sign(
+        """
-    secret_key: bytes, digest: bytes, compressed: bool = True
+        Generate secret key.
-) -> bytes:
+        """
-    """
-    Uses secret key to produce the signature of the digest.
-    """
 
+    def publickey(self, secret_key: bytes, compressed: bool = True) -> bytes:
+        """
+        Computes public key from secret key.
+        """
 
-# extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
+    def sign(
-def verify(public_key: bytes, signature: bytes, digest: bytes) -> bool:
+        self, secret_key: bytes, digest: bytes, compressed: bool = True
-    """
+    ) -> bytes:
-    Uses public key to verify the signature of the digest.
+        """
-    Returns True on success.
+        Uses secret key to produce the signature of the digest.
-    """
+        """
 
+    def verify(
+        self, public_key: bytes, signature: bytes, digest: bytes
+    ) -> bool:
+        """
+        Uses public key to verify the signature of the digest.
+        Returns True on success.
+        """
 
-# extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
+    def verify_recover(self, signature: bytes, digest: bytes) -> bytes:
-def verify_recover(signature: bytes, digest: bytes) -> bytes:
+        """
-    """
+        Uses signature of the digest to verify the digest and recover the public
-    Uses signature of the digest to verify the digest and recover the public
+        key. Returns public key on success, None if the signature is invalid.
-    key. Returns public key on success, None if the signature is invalid.
+        """
-    """
 
-
+    def multiply(self, secret_key: bytes, public_key: bytes) -> bytes:
-# extmod/modtrezorcrypto/modtrezorcrypto-secp256k1_zkp.h
+        """
-def multiply(secret_key: bytes, public_key: bytes) -> bytes:
+        Multiplies point defined by public_key with scalar defined by
-    """
+        secret_key. Useful for ECDH.
-    Multiplies point defined by public_key with scalar defined by
+        """
-    secret_key. Useful for ECDH.
-    """

core/tests/test_trezor.crypto.curve.secp256k1.py

@@ -139,7 +139,7 @@ class TestCryptoSecp256k1(Secp256k1Common, unittest.TestCase):
 
 class TestCryptoSecp256k1Zkp(Secp256k1Common, unittest.TestCase):
     def __init__(self):
-        self.impl = secp256k1_zkp
+        self.impl = secp256k1_zkp.Context()
 
 if __name__ == '__main__':
     unittest.main()