remove function selector computation logic

Author: spencer-xyz

README.md

@@ -199,14 +199,14 @@ signature = sign(message, key)
 
 - `signature`: The generated signature.
 
-### 7. `build_input_text(plaintext, user_aes_key, sender, contract, func_sig, signing_key)`
+### 7. `build_input_text(plaintext, user_aes_key, sender, contract, func_selector, signing_key)`
 
 **Purpose:** Builds input text by encrypting the plaintext and signing it.
 
 **Usage:**
 
 ```python
-int_cipher_text, signature = build_input_text(plaintext, user_aes_key, sender, contract, func_sig, signing_key)
+int_cipher_text, signature = build_input_text(plaintext, user_aes_key, sender, contract, func_selector, signing_key)
 ```
 
 **Parameters:**
@@ -215,22 +215,22 @@ int_cipher_text, signature = build_input_text(plaintext, user_aes_key, sender, c
 - `user_aes_key`: The user's AES key.
 - `sender`: The sender's address.
 - `contract`: The contract address.
-- `func_sig`: The function signature.
+- `func_selector`: The function selector.
 - `signing_key`: The private key used for signing.
 
 **Returns:**
 
 - `int_cipher_text`: The integer representation of the ciphertext.
 - `signature`: The generated signature.
 
-### 8. `build_string_input_text(plaintext, user_aes_key, sender, contract, func_sig, signing_key)`
+### 8. `build_string_input_text(plaintext, user_aes_key, sender, contract, func_selector, signing_key)`
 
 **Purpose:** Builds input text by encrypting the plaintext and signing it.
 
 **Usage:**
 
 ```python
-int_cipher_text, signature = build_string_input_text(plaintext, user_aes_key, sender, contract, func_sig, signing_key)
+int_cipher_text, signature = build_string_input_text(plaintext, user_aes_key, sender, contract, func_selector, signing_key)
 ```
 
 **Parameters:**
@@ -239,7 +239,7 @@ int_cipher_text, signature = build_string_input_text(plaintext, user_aes_key, se
 - `user_aes_key`: The user's AES key.
 - `sender`: The sender's address.
 - `contract`: The contract address.
-- `func_sig`: The function signature.
+- `func_selector`: The function selector.
 - `signing_key`: The private key used for signing.
 
 **Returns:**
@@ -299,43 +299,7 @@ plaintext = decrypt_rsa(private_key_bytes, ciphertext)
 
 - `plaintext`: The decrypted message.
 
-### 12. `keccak256(data)`
-
-**Purpose:** Computes the Keccak-256 hash of the provided data.
-
-**Usage:**
-
-```python
-hash_value = keccak256(data)
-```
-
-**Parameters:**
-
-- `data`: The data to be hashed.
-
-**Returns:**
-
-- `hash_value`: The computed hash.
-
-### 13. `get_func_sig(function_signature)`
-
-**Purpose:** Computes the function signature hash using Keccak-256.
-
-**Usage:**
-
-```python
-func_sig_hash = get_func_sig(function_signature)
-```
-
-**Parameters:**
-
-- `function_signature`: The function signature string.
-
-**Returns:**
-
-- `func_sig_hash`: The first 4 bytes of the computed hash.
-
-### 14. `decrypt_uint(ciphertext, user_key)`
+### 12. `decrypt_uint(ciphertext, user_key)`
 
 **Purpose:** Decrypts a value stored in a contract using a user key
 
@@ -354,7 +318,7 @@ plaintext = decrypt_uint(ciphertext, user_key)
 
 - `result`: The decrypted value.
 
-### 15. `decrypt_string(ciphertext, user_key)`
+### 13. `decrypt_string(ciphertext, user_key)`
 
 **Purpose:** Decrypts a value stored in a contract using a user key
 
@@ -643,25 +607,7 @@ valid, gas_estimate = is_gas_units_estimation_valid(web3, tx)
 - `valid`: Boolean indicating if the gas units are sufficient.
 - `gas_estimate`: The estimated gas units.
 
-### 16. `get_function_signature(function_abi)`
-
-**Purpose:** Generates the function signature from the ABI.
-
-**Usage:**
-
-```python
-func_sig = get_function_signature(function_abi)
-```
-
-**Parameters:**
-
-- `function_abi`: The ABI of the function.
-
-**Returns:**
-
-- `func_sig`: The function signature.
-
-### 17. `deploy_contract(contract, kwargs, tx_params)`
+### 16. `deploy_contract(contract, kwargs, tx_params)`
 
 **Purpose:** Deploys a contract with the given parameters.
 
@@ -681,7 +627,7 @@ tx_receipt = deploy_contract(contract, kwargs, tx_params)
 
 - `tx_receipt`: The transaction receipt.
 
-### 18. `exec_func_via_transaction(func, tx_params)`
+### 17. `exec_func_via_transaction(func, tx_params)`
 
 **Purpose:** Executes a contract function via a transaction.
 
@@ -700,7 +646,7 @@ tx_receipt = exec_func_via_transaction(func, tx_params)
 
 - `tx_receipt`: The transaction receipt.
 
-### 19. `sign_and_send_tx(web3, private_key, transaction)`
+### 18. `sign_and_send_tx(web3, private_key, transaction)`
 
 **Purpose:** Signs and sends a transaction.
 
@@ -720,7 +666,7 @@ tx_receipt = sign_and_send_tx(web3, private_key, transaction)
 
 - `tx_receipt`: The transaction receipt.
 
-### 20. `decrypt_value(contract_value, user_key)`
+### 19. `decrypt_value(contract_value, user_key)`
 
 **Purpose:** Decrypts a value stored in a contract using a user key.
 

coti/crypto_utils.py

@@ -1,5 +1,4 @@
 from Crypto.Cipher import AES
-from Crypto.Hash import keccak
 from Crypto.Random import get_random_bytes
 from cryptography.hazmat.primitives import hashes
 from cryptography.hazmat.primitives import serialization
@@ -10,7 +9,7 @@
 
 block_size = AES.block_size
 address_size = 20
-func_sig_size = 4
+function_selector_size = 4
 ct_size = 32
 key_size = 32
 
@@ -74,22 +73,24 @@ def generate_aes_key():
     return key
 
 
-def sign_input_text(sender, addr, func_sig, ct, key):
+def sign_input_text(sender, addr, function_selector, ct, key):
+    function_selector_bytes = bytes.fromhex(function_selector[2:])
+
     # Ensure all input sizes are the correct length
     if len(sender) != address_size:
         raise ValueError(f"Invalid sender address length: {len(sender)} bytes, must be {address_size} bytes")
     if len(addr) != address_size:
         raise ValueError(f"Invalid contract address length: {len(addr)} bytes, must be {address_size} bytes")
-    if len(func_sig) != func_sig_size:
-        raise ValueError(f"Invalid signature size: {len(func_sig)} bytes, must be {func_sig_size} bytes")
+    if len(function_selector_bytes) != function_selector_size:
+        raise ValueError(f"Invalid signature size: {len(function_selector_bytes)} bytes, must be {function_selector_size} bytes")
     if len(ct) != ct_size:
         raise ValueError(f"Invalid ct length: {len(ct)} bytes, must be {ct_size} bytes")
     # Ensure the key is the correct length
     if len(key) != key_size:
         raise ValueError(f"Invalid key length: {len(key)} bytes, must be {key_size} bytes")
 
     # Create the message to be signed by appending all inputs
-    message = sender + addr + func_sig + ct
+    message = sender + addr + function_selector_bytes + ct
 
     return sign(message, key)
 
@@ -102,7 +103,7 @@ def sign(message, key):
     return signature
 
 
-def build_input_text(plaintext, user_aes_key, sender, contract, func_sig, signing_key):
+def build_input_text(plaintext, user_aes_key, sender, contract, function_selector, signing_key):
     sender_address_bytes = bytes.fromhex(sender.address[2:])
     contract_address_bytes = bytes.fromhex(contract.address[2:])
 
@@ -113,18 +114,16 @@ def build_input_text(plaintext, user_aes_key, sender, contract, func_sig, signin
     ciphertext, r = encrypt(user_aes_key, plaintext_bytes)
     ct = ciphertext + r
 
-    # Create the function signature
-    func_hash = get_func_sig(func_sig)
     # Sign the message
-    signature = sign_input_text(sender_address_bytes, contract_address_bytes, func_hash, ct, signing_key)
+    signature = sign_input_text(sender_address_bytes, contract_address_bytes, function_selector, ct, signing_key)
 
     # Convert the ct to an integer
     int_cipher_text = int.from_bytes(ct, byteorder='big')
 
     return int_cipher_text, signature
 
 
-def build_string_input_text(plaintext, user_aes_key, sender, contract, func_sig, signing_key):
+def build_string_input_text(plaintext, user_aes_key, sender, contract, function_selector, signing_key):
     input_text = {
         'ciphertext': {
             'value': []
@@ -145,7 +144,7 @@ def build_string_input_text(plaintext, user_aes_key, sender, contract, func_sig,
             user_aes_key,
             sender,
             contract,
-            func_sig,
+            function_selector,
             signing_key
         )
 
@@ -173,10 +172,18 @@ def decrypt_uint(ciphertext, user_key):
 
 
 def decrypt_string(ciphertext, user_key):
+    if 'value' in ciphertext or hasattr(ciphertext, 'value'): # format when reading ciphertext from an event
+        __ciphertext = ciphertext['value']
+    elif isinstance(ciphertext, tuple): # format when reading ciphertext from state variable
+        __ciphertext = ciphertext[0]
+    else:
+        raise RuntimeError('Unrecognized ciphertext format')
+
     decrypted_string = ""
 
-    for value in ciphertext['value']:
+    for value in __ciphertext:
         decrypted = decrypt_uint(value, user_key)
+
         byte_length = (decrypted.bit_length() + 7) // 8  # calculate the byte length
 
         # Convert the integer to bytes
@@ -225,26 +232,3 @@ def decrypt_rsa(private_key_bytes, ciphertext):
         )
     )
     return plaintext
-
-
-# Function to compute Keccak-256 hash
-def keccak256(data):
-    # Create Keccak-256 hash object
-    hash_obj = keccak.new(digest_bits=256)
-
-    # Update hash object with data
-    hash_obj.update(data)
-
-    # Compute hash and return
-    return hash_obj.digest()
-
-
-def get_func_sig(function_signature):
-    # Convert function signature to bytes
-    function_signature_bytes = function_signature.encode('utf-8')
-
-    # Compute Keccak-256 hash on the function signature
-    function_signature_bytes_hash = keccak256(function_signature_bytes)
-
-    # Take first 4 bytes of the hash
-    return function_signature_bytes_hash[:4]

coti/utils.py

@@ -111,14 +111,6 @@ def is_gas_units_estimation_valid(web3, tx):
     return False, estimate_gas
 
 
-def get_function_signature(function_abi):
-    # Extract the input types from the ABI
-    input_types = ','.join([param['type'] for param in function_abi.get('inputs', [])])
-
-    # Generate the function signature
-    return f"{function_abi['name']}({input_types})"
-
-
 def deploy_contract(contract, kwargs, tx_params):
     func = contract.constructor(**kwargs)
     return exec_func_via_transaction(func, tx_params)