elements: derive confidential addresses using SLIP-0077

Following #66 and #398, it would allow receiving confidential
transactions to addresses generated on the devices.

Blinding, unblinding and signing will be added in separate PRs.

common/protob/messages-bitcoin.proto

@@ -72,6 +72,7 @@ message GetAddress {
     optional bool show_display = 3;                                     // optionally show on display before sending the result
     optional MultisigRedeemScriptType multisig = 4;                     // filled if we are showing a multisig address
     optional InputScriptType script_type = 5 [default=SPENDADDRESS];    // used to distinguish between various address formats (non-segwit, segwit, etc.)
+    optional bool confidential = 6;                                     // generate confidetial address (for Confidential Transactions)
 }
 
 /**

core/src/apps/wallet/__init__.py

@@ -1,4 +1,4 @@
-from trezor import wire
+from trezor import utils, wire
 from trezor.messages import MessageType
 
 
@@ -13,6 +13,9 @@ def boot() -> None:
         ["secp256k1-groestl"],
         ["secp256k1-smart"],
     ]
+    if not utils.BITCOIN_ONLY:
+        ns.append(["slip21"])
+
     wire.add(MessageType.GetPublicKey, __name__, "get_public_key", ns)
     wire.add(MessageType.GetAddress, __name__, "get_address", ns)
     wire.add(MessageType.GetEntropy, __name__, "get_entropy")

core/src/apps/wallet/get_address.py

@@ -1,3 +1,4 @@
+from trezor import utils
 from trezor.crypto import bip32
 from trezor.messages import InputScriptType
 from trezor.messages.Address import Address
@@ -48,7 +49,17 @@ async def get_address(ctx, msg, keychain):
     )
 
     node = keychain.derive(msg.address_n, coin.curve_name)
-    address = addresses.get_address(msg.script_type, coin, node, msg.multisig)
+    derive_blinding_pubkey = None
+    if not utils.BITCOIN_ONLY and msg.confidential:
+        derive_blinding_pubkey = keychain.derive_slip77_blinding_public_key
+
+    address = addresses.get_address(
+        msg.script_type,
+        coin,
+        node,
+        msg.multisig,
+        derive_blinding_pubkey=derive_blinding_pubkey,
+    )
     address_short = addresses.address_short(coin, address)
     if msg.script_type == InputScriptType.SPENDWITNESS:
         address_qr = address.upper()  # bech32 address

core/src/apps/wallet/sign_tx/addresses.py

@@ -3,14 +3,16 @@
 from trezor.crypto import base58, bech32, cashaddr
 from trezor.crypto.hashlib import sha256
 from trezor.messages import FailureType, InputScriptType
-from trezor.utils import ensure
+from trezor.utils import BITCOIN_ONLY, ensure
 
 from apps.common import HARDENED, address_type, paths
 from apps.common.coininfo import CoinInfo
 from apps.wallet.sign_tx.multisig import multisig_get_pubkeys, multisig_pubkey_index
 from apps.wallet.sign_tx.scripts import (
     output_script_multisig,
     output_script_native_p2wpkh_or_p2wsh,
+    output_script_p2pkh,
+    output_script_p2sh,
 )
 
 if False:
@@ -25,15 +27,19 @@ class AddressError(Exception):
 
 
 def get_address(
-    script_type: InputScriptType, coin: CoinInfo, node, multisig=None
+    script_type: InputScriptType,
+    coin: CoinInfo,
+    node,
+    multisig=None,
+    derive_blinding_pubkey=None,
 ) -> str:
 
+    pubkey = node.public_key()
     if (
         script_type == InputScriptType.SPENDADDRESS
         or script_type == InputScriptType.SPENDMULTISIG
     ):
         if multisig:  # p2sh multisig
-            pubkey = node.public_key()
             index = multisig_pubkey_index(multisig, pubkey)
             if index is None:
                 raise AddressError(FailureType.ProcessError, "Public key not found")
@@ -51,7 +57,7 @@ def get_address(
             raise AddressError(FailureType.ProcessError, "Multisig details required")
 
         # p2pkh
-        address = node.address(coin.address_type)
+        address = address_pkh(pubkey, coin, derive_blinding_pubkey)
         if coin.cashaddr_prefix is not None:
             address = address_to_cashaddr(address, coin)
         return address
@@ -67,7 +73,7 @@ def get_address(
             return address_multisig_p2wsh(pubkeys, multisig.m, coin.bech32_prefix)
 
         # native p2wpkh
-        return address_p2wpkh(node.public_key(), coin)
+        return address_p2wpkh(pubkey, coin)
 
     elif (
         script_type == InputScriptType.SPENDP2SHWITNESS
@@ -79,10 +85,12 @@ def get_address(
         # p2wsh multisig nested in p2sh
         if multisig is not None:
             pubkeys = multisig_get_pubkeys(multisig)
-            return address_multisig_p2wsh_in_p2sh(pubkeys, multisig.m, coin)
+            return address_multisig_p2wsh_in_p2sh(
+                pubkeys, multisig.m, coin, derive_blinding_pubkey
+            )
 
         # p2wpkh nested in p2sh
-        return address_p2wpkh_in_p2sh(node.public_key(), coin)
+        return address_p2wpkh_in_p2sh(pubkey, coin, derive_blinding_pubkey)
 
     else:
         raise AddressError(FailureType.ProcessError, "Invalid script type")
@@ -98,14 +106,16 @@ def address_multisig_p2sh(pubkeys: List[bytes], m: int, coin: CoinInfo):
     return address_p2sh(redeem_script_hash, coin)
 
 
-def address_multisig_p2wsh_in_p2sh(pubkeys: List[bytes], m: int, coin: CoinInfo):
+def address_multisig_p2wsh_in_p2sh(
+    pubkeys: List[bytes], m: int, coin: CoinInfo, derive_blinding_pubkey=None
+):
     if coin.address_type_p2sh is None:
         raise AddressError(
             FailureType.ProcessError, "Multisig not enabled on this coin"
         )
     witness_script = output_script_multisig(pubkeys, m)
     witness_script_hash = sha256(witness_script).digest()
-    return address_p2wsh_in_p2sh(witness_script_hash, coin)
+    return address_p2wsh_in_p2sh(witness_script_hash, coin, derive_blinding_pubkey)
 
 
 def address_multisig_p2wsh(pubkeys: List[bytes], m: int, hrp: str):
@@ -118,27 +128,56 @@ def address_multisig_p2wsh(pubkeys: List[bytes], m: int, hrp: str):
     return address_p2wsh(witness_script_hash, hrp)
 
 
-def address_pkh(pubkey: bytes, coin: CoinInfo) -> str:
-    s = address_type.tobytes(coin.address_type) + coin.script_hash(pubkey)
+def address_pkh(pubkey: bytes, coin: CoinInfo, derive_blinding_pubkey=None) -> str:
+    script_hash = coin.script_hash(pubkey)
+    address_type_prefix = address_type.tobytes(coin.address_type)
+    if not BITCOIN_ONLY and derive_blinding_pubkey:
+        script = output_script_p2pkh(script_hash)
+        blinding_pubkey = derive_blinding_pubkey(script=script)
+        s = (
+            address_type.tobytes(coin.confidential_assets["address_prefix"])
+            + address_type_prefix
+            + blinding_pubkey
+            + script_hash
+        )
+    else:
+        s = address_type_prefix + script_hash
     return base58.encode_check(bytes(s), coin.b58_hash)
 
 
-def address_p2sh(redeem_script_hash: bytes, coin: CoinInfo) -> str:
-    s = address_type.tobytes(coin.address_type_p2sh) + redeem_script_hash
+def address_p2sh(
+    redeem_script_hash: bytes, coin: CoinInfo, derive_blinding_pubkey=None
+) -> str:
+    address_type_prefix = address_type.tobytes(coin.address_type_p2sh)
+    if not BITCOIN_ONLY and derive_blinding_pubkey:
+        script = output_script_p2sh(redeem_script_hash)
+        blinding_pubkey = derive_blinding_pubkey(script=script)
+        s = (
+            address_type.tobytes(coin.confidential_assets["address_prefix"])
+            + address_type_prefix
+            + blinding_pubkey
+            + redeem_script_hash
+        )
+    else:
+        s = address_type_prefix + redeem_script_hash
     return base58.encode_check(bytes(s), coin.b58_hash)
 
 
-def address_p2wpkh_in_p2sh(pubkey: bytes, coin: CoinInfo) -> str:
+def address_p2wpkh_in_p2sh(
+    pubkey: bytes, coin: CoinInfo, derive_blinding_pubkey=None
+) -> str:
     pubkey_hash = ecdsa_hash_pubkey(pubkey, coin)
     redeem_script = output_script_native_p2wpkh_or_p2wsh(pubkey_hash)
     redeem_script_hash = coin.script_hash(redeem_script)
-    return address_p2sh(redeem_script_hash, coin)
+    return address_p2sh(redeem_script_hash, coin, derive_blinding_pubkey)
 
 
-def address_p2wsh_in_p2sh(witness_script_hash: bytes, coin: CoinInfo) -> str:
+def address_p2wsh_in_p2sh(
+    witness_script_hash: bytes, coin: CoinInfo, derive_blinding_pubkey=None
+) -> str:
     redeem_script = output_script_native_p2wpkh_or_p2wsh(witness_script_hash)
     redeem_script_hash = coin.script_hash(redeem_script)
-    return address_p2sh(redeem_script_hash, coin)
+    return address_p2sh(redeem_script_hash, coin, derive_blinding_pubkey)
 
 
 def address_p2wpkh(pubkey: bytes, coin: CoinInfo) -> str:

core/src/trezor/messages/GetAddress.py

@@ -23,12 +23,14 @@ def __init__(
         show_display: bool = None,
         multisig: MultisigRedeemScriptType = None,
         script_type: EnumTypeInputScriptType = None,
+        confidential: bool = None,
     ) -> None:
         self.address_n = address_n if address_n is not None else []
         self.coin_name = coin_name
         self.show_display = show_display
         self.multisig = multisig
         self.script_type = script_type
+        self.confidential = confidential
 
     @classmethod
     def get_fields(cls) -> Dict:
@@ -38,4 +40,5 @@ def get_fields(cls) -> Dict:
             3: ('show_display', p.BoolType, 0),
             4: ('multisig', MultisigRedeemScriptType, 0),
             5: ('script_type', p.EnumType("InputScriptType", (0, 1, 2, 3, 4)), 0),  # default=SPENDADDRESS
+            6: ('confidential', p.BoolType, 0),
         }

python/src/trezorlib/btc.py

@@ -46,6 +46,7 @@ def get_address(
     show_display=False,
     multisig=None,
     script_type=messages.InputScriptType.SPENDADDRESS,
+    confidential=False,
 ):
     return client.call(
         messages.GetAddress(
@@ -54,6 +55,7 @@ def get_address(
             show_display=show_display,
             multisig=multisig,
             script_type=script_type,
+            confidential=confidential,
         )
     )
 

python/src/trezorlib/cli/btc.py

@@ -52,13 +52,19 @@ def cli():
 @click.option("-n", "--address", required=True, help="BIP-32 path")
 @click.option("-t", "--script-type", type=ChoiceType(INPUT_SCRIPTS), default="address")
 @click.option("-d", "--show-display", is_flag=True)
+@click.option("--confidential", type=bool)
 @click.pass_obj
-def get_address(connect, coin, address, script_type, show_display):
+def get_address(connect, coin, address, script_type, show_display, confidential):
     """Get address for specified path."""
     coin = coin or DEFAULT_COIN
     address_n = tools.parse_path(address)
     return btc.get_address(
-        connect(), coin, address_n, show_display, script_type=script_type
+        connect(),
+        coin,
+        address_n,
+        show_display,
+        script_type=script_type,
+        confidential=confidential,
     )
 
 

python/src/trezorlib/messages/GetAddress.py

@@ -23,12 +23,14 @@ def __init__(
         show_display: bool = None,
         multisig: MultisigRedeemScriptType = None,
         script_type: EnumTypeInputScriptType = None,
+        confidential: bool = None,
     ) -> None:
         self.address_n = address_n if address_n is not None else []
         self.coin_name = coin_name
         self.show_display = show_display
         self.multisig = multisig
         self.script_type = script_type
+        self.confidential = confidential
 
     @classmethod
     def get_fields(cls) -> Dict:
@@ -38,4 +40,5 @@ def get_fields(cls) -> Dict:
             3: ('show_display', p.BoolType, 0),
             4: ('multisig', MultisigRedeemScriptType, 0),
             5: ('script_type', p.EnumType("InputScriptType", (0, 1, 2, 3, 4)), 0),  # default=SPENDADDRESS
+            6: ('confidential', p.BoolType, 0),
         }

tests/device_tests/test_msg_getaddress.py

@@ -117,10 +117,27 @@ def test_grs(self, client):
         )
 
     @pytest.mark.altcoin
+    @pytest.mark.setup_client(mnemonic=MNEMONIC12)
     def test_elements(self, client):
         assert (
-            btc.get_address(client, "Elements", parse_path("m/44'/1'/0'/0/0"))
-            == "2dpWh6jbhAowNsQ5agtFzi7j6nKscj6UnEr"
+            btc.get_address(
+                client,
+                "Elements",
+                parse_path("m/44'/1'/0'/0/0"),
+                script_type=proto.InputScriptType.SPENDADDRESS,
+                confidential=True,
+            )
+            == "CTExueKM8363z7gaDiD22BKuYCcj8peAtgDTndcdUFn4s47jgBHAsTk1WrpL3GJkVJzuRdnvU56ma3MQ"
+        )
+        assert (
+            btc.get_address(
+                client,
+                "Elements",
+                parse_path("m/44'/1'/0'/0/0"),
+                script_type=proto.InputScriptType.SPENDADDRESS,
+                confidential=False,
+            )
+            == "2dekDMTvVnZjAZVFRrs8mRAhyXKHGptx5pd"
         )
 
     @pytest.mark.multisig

tests/device_tests/test_msg_getaddress_segwit.py

@@ -80,14 +80,27 @@ def test_show_segwit_altcoin(self, client):
             )
             == "2N4Q5FhU2497BryFfUgbqkAJE87aKDv3V3e"
         )
+
+    @pytest.mark.altcoin
+    @pytest.mark.setup_client(mnemonic=" ".join(["all"] * 12))
+    def test_elements(self, client):
+        assert (
+            btc.get_address(
+                client,
+                "Elements",
+                parse_path("m/49'/1'/0'/0/0"),
+                script_type=proto.InputScriptType.SPENDP2SHWITNESS,
+                confidential=True,
+            )
+            == "AzpuzTFTuET7YqJ9U8fBuRTf5xvsLmudLg3uvycfP1aTFpKXUYuUs3kz98boyzDSe5n1MevURZdB4pR5"
+        )
         assert (
             btc.get_address(
                 client,
                 "Elements",
                 parse_path("m/49'/1'/0'/0/0"),
-                False,
-                None,
                 script_type=proto.InputScriptType.SPENDP2SHWITNESS,
+                confidential=False,
             )
             == "XNW67ZQA9K3AuXPBWvJH4zN2y5QBDTwy2Z"
         )

tests/device_tests/test_msg_getaddress_segwit_native.py

@@ -80,6 +80,10 @@ def test_show_segwit_altcoin(self, client):
             )
             == "grs1qw4teyraux2s77nhjdwh9ar8rl9dt7zww8r6lne"
         )
+
+    @pytest.mark.altcoin
+    @pytest.mark.setup_client(mnemonic=" ".join(["all"] * 12))
+    def test_elements(self, client):
         assert (
             btc.get_address(
                 client,