Merge pull request #31 from kuronosec/review-circuits

Modify circom circuits to improve user privacy

builder/Dockerfile_Debian

@@ -18,7 +18,9 @@ RUN pip install --trusted-host pypi.python.org --no-cache-dir -r /tmp/requiremen
 RUN mkdir /packages && chmod 777 /packages
 
 COPY src /zk-firma-digital_base
-COPY build /zk-artifacts
+COPY build/firma-verifier.zkey /zk-artifacts/firma-verifier.zkey
+COPY build/firma-verifier_js /zk-artifacts/firma-verifier_js
+COPY build/vkey.json /zk-artifacts/vkey.json
 
 COPY builder/debian/copyright /tmp/copyright
 COPY builder/debian/postinst /tmp/postinst

builder/build_linux.sh

@@ -2,7 +2,7 @@
 
 set -xe
 
-VERSION=0.4
+VERSION=0.5
 NAME='zk-firma-digital'
 PACKAGE='zk-firma-digital'
 ARCH='amd64'

builder/entrypoint_debian.sh

@@ -6,8 +6,8 @@ cd /zk-firma-digital/
 
 # Create binary installer for the app
 pyinstaller --clean --onefile -n zk-firma-digital --upx-dir=/usr/local/share/  \
-    --noconfirm --log-level=WARN --windowed --distpath=/data/ --workpath=/tmp/zk-firma-digital_build \
-    --hidden-import 'pkcs11.defaults' main.py
+    --noconfirm --log-level=WARN --windowed --distpath=/data/ \
+    --workpath=/tmp/zk-firma-digital_build main.py
 
 mkdir -p /data/build/
 cd  /data/build/
@@ -66,7 +66,7 @@ cp /zk-firma-digital/os_libs/linux/${ARCH}/libASEP11.so \
 cp -a /zk-firma-digital/CA-certificates/ $DEB_HOMEDIR/usr/share/zk-firma-digital/
 cp -a /zk-artifacts/firma-verifier_js $DEB_HOMEDIR/usr/share/zk-firma-digital/zk-artifacts
 cp -a /zk-artifacts/vkey.json $DEB_HOMEDIR/usr/share/zk-firma-digital/zk-artifacts
-# cp -a /zk-artifacts/firma-verifier.zkey $DEB_HOMEDIR/usr/share/zk-firma-digital/zk-artifacts
+cp -a /zk-artifacts/firma-verifier.zkey $DEB_HOMEDIR/usr/share/zk-firma-digital/zk-artifacts
 
 dpkg-deb --build --root-owner-group $DEB_HOMEDIR
 alien -t $DEB_HOMEDIR.deb --scripts

circuits/firma-certificate-verifier.circom

@@ -19,7 +19,7 @@ include "./helpers/nullifier.circom";
 /// @input nullifierSeed A random value used as an input to compute the nullifier; for example: applicationId, actionId
 /// @input public signalHash Any message to commit to (to make it part of the proof)
 /// @output pubkeyHash Poseidon hash of the RSA public key (after merging nearby chunks)
-/// @output nullifier A unique value derived from nullifierSeed and Firma Digital data to nullify the proof/user
+/// @output nullifier A unique value derived from nullifierSeed and the signature data to nullify the proof/user
 /// @output timestamp Timestamp of when the data was signed - extracted and converted to Unix timestamp
 /// @output ageAbove18 Boolean flag indicating age is above 18; 0 if not revealed
 template FirmaDigitalCRVerifier(n, k, maxDataLength) {
@@ -28,6 +28,7 @@ template FirmaDigitalCRVerifier(n, k, maxDataLength) {
     signal input signature[k];
     signal input pubKey[k];
     signal input revealAgeAbove18;
+    signal input userSignature[k];
 
     // Public inputs
     signal input nullifierSeed;
@@ -59,9 +60,8 @@ template FirmaDigitalCRVerifier(n, k, maxDataLength) {
     // For Firma CR, age is always above 18
     ageAbove18 <== revealAgeAbove18 * 1;
 
-    // TODO: create an actual Nullifier
     // Calculate nullifier
-    nullifier <== Nullifier(n, k)(nullifierSeed, signature);
+    nullifier <== Nullifier(n, k)(nullifierSeed, userSignature);
 
     // Dummy square to prevent signal tampering
     // (in rare cases where non-constrained inputs are ignored)

circuits/helpers/signature.circom

@@ -10,7 +10,8 @@ include "@zk-email/circuits/lib/sha.circom";
 /// @param n - RSA pubic key size per chunk
 /// @param k - Number of chunks the RSA public key is split into
 /// @param maxDataLength - Maximum length of the data
-/// @input certDataPadded - cert data without the signature; each number represent ascii byte; remaining space is padded with 0
+/// @input certDataPadded - cert data without the signature;
+/// each number represent ascii byte; remaining space is padded with 0
 /// @input certDataPaddedLength - Length of padded cert data
 /// @input signature - RSA signature
 /// @input pubKey - RSA public key
@@ -55,8 +56,10 @@ template SignatureVerifier(n, k, maxDataLength) {
 	rsa.signature <== signature;
 
   // Calculate Poseidon hash of the public key (609 constraints)
-  // Poseidon component can take only 16 inputs, so we convert k chunks to k/2 chunks.
-  // We are assuming k is > 16 and <= 32 (i.e we merge two consecutive item in array to bring down the size)
+  // Poseidon component can take only 16 inputs, so we convert k chunks
+  // to k/2 chunks.
+  // We are assuming k is > 16 and <= 32 (i.e we merge two consecutive
+  // item in array to bring down the size)
   var poseidonInputSize = k \ 2;
   if (k % 2 == 1) {
       poseidonInputSize++;

src/circom.py

@@ -1,7 +1,7 @@
 #!python
 
 # Import the necessary libraries
-import os.path
+import os
 
 from zkpy.circuit import Circuit, GROTH, PLONK, FFLONK
 from zkpy.ptau import PTau
@@ -10,14 +10,15 @@
 # This class provides utilitis to compile the circom circuts
 # fot the Firma Digital
 class Circom():
-    def __init__(self) -> None:
+    def __init__(self, _type="runtime") -> None:
         # Define variables
-        self.config = Configuration()
+        self.config = Configuration(type=_type)
 
         # Create comilation object
         print("Open circuit")
         self.circuit = Circuit(circ_file=self.config.circ_file,
-                        output_dir=self.config.output_dir,
+                        output_dir=str(self.config.output_dir),
+                        node_module_dir=self.config.node_module_dir,
                         js_dir=self.config.js_dir,
                         r1cs=self.config.r1cs,
                         sym_file=self.config.sym_file,
@@ -32,17 +33,21 @@ def __init__(self) -> None:
 
     # Actually compile or circom code
     def compile_circuit(self) -> None:
-        print("Compile circuit")
-        self.circuit.compile()
-        self.circuit.check_circ_compiled()
-        print("Get info")
-        self.circuit.get_info()
+        if not self.circuit.check_circ_compiled():
+            print("Compile circuit")
+            if not os.path.exists(self.config.output_dir):
+                os.makedirs(self.config.output_dir)
+            self.circuit.compile()
+            print("Get info")
+            self.circuit.get_info()
+        else:
+            print("Circuit already compiled.")
 
     # Start the Power of Tau ceremony
     # TODO: allow contributions
     def power_of_tau(self) -> None:
-        print("Power of Tau ceremony")
         if(not os.path.isfile(self.config.ptau_file)):
+            print("Power of Tau ceremony")
             print("start()")
             self.ptau.start(curve='bn128', constraints='23')
             print("contribute()")
@@ -51,26 +56,38 @@ def power_of_tau(self) -> None:
             self.ptau.beacon()
             print("prep_phase2()")
             self.ptau.prep_phase2()
+        else:
+            print("power_of_tau already done")
 
     # Create the input from the user in a way snarks undertands it
     def generate_witness(self) -> None:
-        if(not os.path.isfile(self.config.witness)):
-            print("circuit.gen_witness")
-            self.circuit.gen_witness(self.config.input_file)
+        print("circuit.gen_witness")
+        self.circuit.gen_witness(
+            self.config.input_file,
+            output_file=self.config.witness)
 
     # Setup the keys based on the ceremony
     def setup(self) -> None:
         if(not os.path.isfile(self.config.output_file)):
             print("setup")
             self.circuit.setup(GROTH, self.ptau)
+        else:
+            print("Setup already done")
 
     # Calculate the ZK proof based on the circuit and the key
     def prove(self) -> None:
         print("prove")
         self.circuit.prove(GROTH)
-        print("export_vkey")
-        self.circuit.export_vkey(zkey_file=self.config.zkey_file,
-                            output_file=self.config.output_file)
+
+    def export_vkey(self) -> None:
+        if not os.path.isfile(self.config.output_file):
+            print("export_vkey")
+            self.circuit.export_vkey(
+                zkey_file=str(self.config.output_dir)+'/firma-verifier.zkey',
+                output_file=self.config.output_file
+            )
+        else:
+            print("export_vkey already done")
 
     # Verify that the created user ZK proof is valida for the circuit
     # i.e. the users posses a Firma Digital but we don't any information
@@ -86,7 +103,8 @@ def verify(self) -> None:
 
 # Runs the full compilation process
 if __name__ == "__main__":
-    circom = Circom()
+    circom = Circom(_type="compile")
     circom.compile_circuit()
     circom.power_of_tau()
-    circom.setup()
+    circom.setup()
+    circom.export_vkey()

src/configuration.py

@@ -7,7 +7,7 @@
 os_type = platform.system()
 
 class Configuration:
-    def __init__(self) -> None:
+    def __init__(self, type="runtime") -> None:
         # Define OS specific paths
         # Check what operation system we re running on
         if os_type == 'Windows':
@@ -20,7 +20,6 @@ def __init__(self) -> None:
             print("Unknown operating system")
 
         self.user_path = os.path.join(Path.home(), Path('.zk-firma-digital/'))
-        self.build_path = Path("build/")
 
         self.credentials_path = os.path.join(self.user_path, Path('credentials/'))
         self.credential_file = os.path.join(self.credentials_path, Path('credential.json'))
@@ -32,14 +31,19 @@ def __init__(self) -> None:
                                          Path('CA-certificates/certificado-cadena-confianza.pem'))
         self.JWT_cert_path = os.path.join(self.installation_path,
                                          Path('CA-certificates/JWT_public_key.pem'))
-        self.output_dir = os.path.join(self.user_path, self.build_path)
         self.credentials_path = self.credentials_path
 
         # Define where to find the diferent components
         # of thew compilation process
-
+        if type == "compile":
+            self.build_path = Path("../build/")
+            self.output_dir = self.build_path
+            self.js_dir = os.path.join(self.build_path, Path('firma-verifier_js/'))
+        elif type == "runtime":
+            self.build_path = Path("build/")
+            self.output_dir = os.path.join(self.user_path, self.build_path)
+            self.js_dir = os.path.join(self.zk_artifacts_path, Path('firma-verifier_js/'))
         # Files for proof and verification
-        self.js_dir = os.path.join(self.zk_artifacts_path, Path('firma-verifier_js/'))
         self.vkey_file = os.path.join(self.zk_artifacts_path, Path('vkey.json'))
         self.wasm = os.path.join(self.js_dir, Path('firma-verifier.wasm'))
 
@@ -54,5 +58,5 @@ def __init__(self) -> None:
         self.r1cs = os.path.join(self.output_dir, Path('firma-verifier.r1cs'))
         self.sym_file = os.path.join(self.output_dir, Path('firma-verifier.sym'))
         self.ptau_file = os.path.join(self.output_dir, Path('firma-verifier-final.ptau'))
-        self.circ_file = '../circuits/firma-verifier.circom'
-
+        self.circ_file = Path('../circuits/firma-verifier.circom')
+        self.node_module_dir = Path('../circuits/node_modules/')

src/main.py

@@ -6,7 +6,6 @@
 import json
 import datetime
 import logging
-import jwt
 from urllib.parse import urlparse, parse_qs
 
 # We will use the PyQt6 to provide a grafical interface for the user

src/signature.py

@@ -1,7 +1,6 @@
 # Import required libraries
 import json
 import hashlib
-import base64
 import os
 import datetime
 import binascii
@@ -130,3 +129,42 @@ def sign_file(self, file_path):
             logging.error(message+" "+str(error), exc_info=True)
             return message
         return "Se firmó el archivo correctamente!"
+
+    def sign_data(self, data_to_sign):
+        # Open a session with the token
+        slots = self.pkcs11.getSlotList(tokenPresent=True)
+        if not slots:
+            raise Exception("No token found")
+
+        slot = slots[0]
+
+        session = None
+
+        try:
+            session = self.pkcs11.openSession(slot, PyKCS11.CKF_SERIAL_SESSION | PyKCS11.CKF_RW_SESSION)
+
+            # Login with your PIN
+            session.login(self.pin)
+
+            # Find the private key object
+            private_key = session.findObjects([(PyKCS11.CKA_CLASS, PyKCS11.CKO_PRIVATE_KEY)])[0]
+
+            # Canonicalize and hash the JSON data (using SHA-256)
+            hashed_data = hashlib.sha256(data_to_sign).hexdigest()
+
+            # Sign the hash using the private key
+            mechanism = PyKCS11.Mechanism(PyKCS11.CKM_SHA256_RSA_PKCS, None)
+            signature = session.sign(private_key, hashed_data, mechanism)
+
+            # Logout and close the session
+            session.logout()
+            session.closeSession()
+
+            return signature
+        except PyKCS11Error as error:
+            message = """Hubo un error al leer la tarjeta,\
+                         por favor verifique que esta conectada correctamente\
+                         y que ingreso el pin correcto."""
+            logging.error(message+" "+str(error), exc_info=True)
+            return message
+        return "Se firmó el archivo correctamente!"

src/verification.py

@@ -1,5 +1,4 @@
 # Import the required libraries
-import base64
 import json
 import os
 import sys
@@ -9,6 +8,7 @@
 from asn1crypto import pem, x509
 from certvalidator import CertificateValidator, ValidationContext, errors
 from configuration import Configuration
+from signature import Signature
 
 # This class helps to validate the certificate extracted from the smart card
 # to see if it actually was signed by the goverment chain of trust
@@ -19,6 +19,7 @@ def __init__(self, pin, signal_hash=None):
         self.config = Configuration()
         self.user_path = self.config.user_path
         self.credentials_path=self.config.credentials_path
+        self.user_signature = Signature(pin)
 
         # We have a folder with the goverment certificates
         self.root_CA_path = self.config.root_CA_path
@@ -98,6 +99,12 @@ def get_certificate_info(self, cert, root_cert):
 
         # Nullifier seed
         nullifier_seed = int.from_bytes(os.urandom(4), sys.byteorder)
+        self.user_signature.load_library()
+        user_signature = self.user_signature.sign_data(tbs_bytes)
+        # Convert the signature to a big integer
+        user_signature_int = int.from_bytes(user_signature, byteorder='big')
+        # Print the big integer in chunks
+        user_signature_str = splitToWords(user_signature_int, 121, 17)
 
         if signature_str is not None:
             json_data = {
@@ -107,7 +114,8 @@ def get_certificate_info(self, cert, root_cert):
                     "pubKey": public_key_str,
                     "nullifierSeed": str(nullifier_seed),
                     "signalHash": signal_hash,
-                    "revealAgeAbove18": "1"
+                    "revealAgeAbove18": "1",
+                    "userSignature": user_signature_str
             }
             json_data = json.dumps(json_data, indent=4)
             with open(self.config.input_file, 'w') as json_file: