From 2c0463c079396e54872e6628760fe041a06c9bba Mon Sep 17 00:00:00 2001
From: Spencer Miller <spencer.github.123@gmail.com>
Date: Sun, 18 Aug 2024 10:35:56 +0300
Subject: [PATCH 1/4] update string encryption/decryption

---
 README.md            | 39 +++++++++++++++++++++++-------
 coti/crypto_utils.py | 56 ++++++++++++++++++++++++++++++--------------
 2 files changed, 69 insertions(+), 26 deletions(-)

diff --git a/README.md b/README.md
index ad5816c..73c8f67 100644
--- a/README.md
+++ b/README.md
@@ -223,7 +223,30 @@ int_cipher_text, signature = build_input_text(plaintext, user_aes_key, sender, c
 - `int_cipher_text`: The integer representation of the ciphertext.
 - `signature`: The generated signature.
 
-### 8. `generate_rsa_keypair()`
+### 8. `build_string_input_text(plaintext, user_aes_key, sender, contract, func_sig, 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)
+```
+
+**Parameters:**
+
+- `plaintext`: The plaintext message.
+- `user_aes_key`: The user's AES key.
+- `sender`: The sender's address.
+- `contract`: The contract address.
+- `func_sig`: The function signature.
+- `signing_key`: The private key used for signing.
+
+**Returns:**
+
+- `input_text`: A dictionary of the form { "ciphertext": { "value": int[] }, "signature": bytes[] }
+
+### 9. `generate_rsa_keypair()`
 
 **Purpose:** Generates an RSA key pair.
 
@@ -238,7 +261,7 @@ private_key_bytes, public_key_bytes = generate_rsa_keypair()
 - `private_key_bytes`: The serialized private key.
 - `public_key_bytes`: The serialized public key.
 
-### 9. `encrypt_rsa(public_key_bytes, plaintext)`
+### 10. `encrypt_rsa(public_key_bytes, plaintext)`
 
 **Purpose:** Encrypts plaintext using RSA encryption with a provided public key.
 
@@ -257,7 +280,7 @@ ciphertext = encrypt_rsa(public_key_bytes, plaintext)
 
 - `ciphertext`: The encrypted message.
 
-### 10. `decrypt_rsa(private_key_bytes, ciphertext)`
+### 11. `decrypt_rsa(private_key_bytes, ciphertext)`
 
 **Purpose:** Decrypts ciphertext using RSA decryption with a provided private key.
 
@@ -276,7 +299,7 @@ plaintext = decrypt_rsa(private_key_bytes, ciphertext)
 
 - `plaintext`: The decrypted message.
 
-### 11. `keccak256(data)`
+### 12. `keccak256(data)`
 
 **Purpose:** Computes the Keccak-256 hash of the provided data.
 
@@ -294,7 +317,7 @@ hash_value = keccak256(data)
 
 - `hash_value`: The computed hash.
 
-### 12. `get_func_sig(function_signature)`
+### 13. `get_func_sig(function_signature)`
 
 **Purpose:** Computes the function signature hash using Keccak-256.
 
@@ -312,7 +335,7 @@ func_sig_hash = get_func_sig(function_signature)
 
 - `func_sig_hash`: The first 4 bytes of the computed hash.
 
-### 13. `decrypt_uint(ciphertext, user_key)`
+### 14. `decrypt_uint(ciphertext, user_key)`
 
 **Purpose:** Decrypts a value stored in a contract using a user key
 
@@ -331,7 +354,7 @@ plaintext = decrypt_uint(ciphertext, user_key)
 
 - `result`: The decrypted value.
 
-### 14. `decrypt_string(ciphertext, user_key)`
+### 15. `decrypt_string(ciphertext, user_key)`
 
 **Purpose:** Decrypts a value stored in a contract using a user key
 
@@ -343,7 +366,7 @@ plaintext = decrypt_string(ciphertext, user_key)
 
 **Parameters:**
 
-- `ciphertext`: The value to be decrypted.
+- `ciphertext`: A dictionary of the form { "value": int[] } where each cell holds up to 8 characters (padded at the end with zeroes) encrypted
 - `userKey`: The user's AES key.
 
 **Returns:**
diff --git a/coti/crypto_utils.py b/coti/crypto_utils.py
index 804d2ce..8714746 100644
--- a/coti/crypto_utils.py
+++ b/coti/crypto_utils.py
@@ -1,6 +1,3 @@
-import binascii
-from array import array
-
 from Crypto.Cipher import AES
 from Crypto.Hash import keccak
 from Crypto.Random import get_random_bytes
@@ -9,6 +6,7 @@
 from cryptography.hazmat.primitives.asymmetric import padding
 from cryptography.hazmat.primitives.asymmetric import rsa
 from eth_keys import keys
+from math import ceil
 
 block_size = AES.block_size
 address_size = 20
@@ -24,6 +22,7 @@ def encrypt(key, plaintext):
 
     # Ensure key size is 128 bits (16 bytes)
     if len(key) != block_size:
+        print(len(key), block_size)
         raise ValueError("Key size must be 128 bits.")
 
     # Create a new AES cipher block using the provided key
@@ -126,14 +125,34 @@ def build_input_text(plaintext, user_aes_key, sender, contract, func_sig, signin
 
 
 def build_string_input_text(plaintext, user_aes_key, sender, contract, func_sig, signing_key):
-    encoded_plaintext = array('B', plaintext.encode('utf-8'))
-    encrypted_str = [{'ciphertext': 0, 'signature': b''} for _ in range(len(encoded_plaintext))]
-    for i in range(len(encoded_plaintext)):
-        ct_int, signature = build_input_text(int(encoded_plaintext[i]), user_aes_key, sender, contract,
-                                             func_sig, signing_key)
-        encrypted_str[i] = {'ciphertext': ct_int, 'signature': signature}
+    input_text = {
+        'ciphertext': {
+            'value': []
+        },
+        'signature': []
+    }
+
+    encoded_plaintext = bytearray(list(plaintext.encode('utf-8')))
+
+    for i in range(ceil(len(encoded_plaintext) / 8)):
+        start_idx = i * 8
+        end_idx = min(start_idx + 8, len(encoded_plaintext))
+
+        byte_arr = encoded_plaintext[start_idx:end_idx] + bytearray(8 - (end_idx - start_idx))
+
+        ct_int, sig = build_input_text(
+            int.from_bytes(byte_arr, 'big'),
+            user_aes_key,
+            sender,
+            contract,
+            func_sig,
+            signing_key
+        )
 
-    return encrypted_str
+        input_text['ciphertext']['value'].append(ct_int)
+        input_text['signature'].append(sig)
+    
+    return input_text
 
 
 def decrypt_uint(ciphertext, user_key):
@@ -154,18 +173,19 @@ def decrypt_uint(ciphertext, user_key):
 
 
 def decrypt_string(ciphertext, user_key):
-    string_from_input_tx = ""
-    for input_text_from_tx in ciphertext:
-        decrypted_input_from_tx = decrypt_uint(input_text_from_tx, user_key)
-        byte_length = (decrypted_input_from_tx.bit_length() + 7) // 8  # calculate the byte length
+    decrypted_string = ""
+
+    for value in ciphertext['value']:
+        decrypted = decrypt_uint(value, user_key)
+        byte_length = (decrypted.bit_length() + 7) // 8  # calculate the byte length
 
         # Convert the integer to bytes
-        decrypted_bytes = decrypted_input_from_tx.to_bytes(byte_length, byteorder='big')
+        decrypted_bytes = decrypted.to_bytes(byte_length, byteorder='big')
 
         # Decode the bytes to a string
-        string_from_input_tx += decrypted_bytes.decode('utf-8')
-
-    return string_from_input_tx
+        decrypted_string += decrypted_bytes.decode('utf-8')
+    
+    return decrypted_string.strip('\0')
 
 
 def generate_rsa_keypair():

From 9126ab942f0c82d422b8b322ca2625e63c6d5df5 Mon Sep 17 00:00:00 2001
From: Spencer Miller <spencer.github.123@gmail.com>
Date: Sun, 18 Aug 2024 17:45:25 +0300
Subject: [PATCH 2/4] remove function selector computation logic

---
 README.md            | 78 +++++++-------------------------------------
 coti/crypto_utils.py | 56 ++++++++++++-------------------
 coti/utils.py        |  8 -----
 3 files changed, 32 insertions(+), 110 deletions(-)

diff --git a/README.md b/README.md
index 73c8f67..45dcc3b 100644
--- a/README.md
+++ b/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:**
@@ -215,7 +215,7 @@ 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:**
@@ -223,14 +223,14 @@ int_cipher_text, signature = build_input_text(plaintext, user_aes_key, sender, c
 - `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.
 
diff --git a/coti/crypto_utils.py b/coti/crypto_utils.py
index 8714746..483d4f3 100644
--- a/coti/crypto_utils.py
+++ b/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
 
@@ -74,14 +73,16 @@ 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
@@ -89,7 +90,7 @@ def sign_input_text(sender, addr, func_sig, ct, key):
         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:])
 
@@ -113,10 +114,8 @@ 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')
@@ -124,7 +123,7 @@ def build_input_text(plaintext, user_aes_key, sender, contract, func_sig, signin
     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]
diff --git a/coti/utils.py b/coti/utils.py
index 932fc3d..6e7149e 100644
--- a/coti/utils.py
+++ b/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)

From 5a24b5df85dea21ff8bcecfd988c120dd5c446ad Mon Sep 17 00:00:00 2001
From: Spencer Miller <spencer.github.123@gmail.com>
Date: Sun, 29 Sep 2024 09:14:09 +0300
Subject: [PATCH 3/4] update uint encryption

---
 coti/crypto_utils.py | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/coti/crypto_utils.py b/coti/crypto_utils.py
index 483d4f3..435ad85 100644
--- a/coti/crypto_utils.py
+++ b/coti/crypto_utils.py
@@ -5,7 +5,6 @@
 from cryptography.hazmat.primitives.asymmetric import padding
 from cryptography.hazmat.primitives.asymmetric import rsa
 from eth_keys import keys
-from math import ceil
 
 block_size = AES.block_size
 address_size = 20
@@ -21,7 +20,6 @@ def encrypt(key, plaintext):
 
     # Ensure key size is 128 bits (16 bytes)
     if len(key) != block_size:
-        print(len(key), block_size)
         raise ValueError("Key size must be 128 bits.")
 
     # Create a new AES cipher block using the provided key
@@ -120,7 +118,10 @@ def build_input_text(plaintext, user_aes_key, sender, contract, function_selecto
     # Convert the ct to an integer
     int_cipher_text = int.from_bytes(ct, byteorder='big')
 
-    return int_cipher_text, signature
+    return {
+        'ciphertext': int_cipher_text,
+        'signature': signature
+    }
 
 
 def build_string_input_text(plaintext, user_aes_key, sender, contract, function_selector, signing_key):
@@ -133,13 +134,12 @@ def build_string_input_text(plaintext, user_aes_key, sender, contract, function_
 
     encoded_plaintext = bytearray(list(plaintext.encode('utf-8')))
 
-    for i in range(ceil(len(encoded_plaintext) / 8)):
-        start_idx = i * 8
+    for start_idx in range(0, len(encoded_plaintext), 8):
         end_idx = min(start_idx + 8, len(encoded_plaintext))
 
         byte_arr = encoded_plaintext[start_idx:end_idx] + bytearray(8 - (end_idx - start_idx))
 
-        ct_int, sig = build_input_text(
+        it_int = build_input_text(
             int.from_bytes(byte_arr, 'big'),
             user_aes_key,
             sender,
@@ -148,8 +148,8 @@ def build_string_input_text(plaintext, user_aes_key, sender, contract, function_
             signing_key
         )
 
-        input_text['ciphertext']['value'].append(ct_int)
-        input_text['signature'].append(sig)
+        input_text['ciphertext']['value'].append(it_int['ciphertext'])
+        input_text['signature'].append(it_int['signature'])
     
     return input_text
 

From ba8c6444bf1e6511639f26a1bd839f96182bc0f5 Mon Sep 17 00:00:00 2001
From: Spencer Miller <spencer.github.123@gmail.com>
Date: Sun, 29 Sep 2024 09:22:15 +0300
Subject: [PATCH 4/4] add support for ctAddress

---
 README.md            | 52 ++++++++++++++++++++++++++++++----
 coti/crypto_utils.py | 67 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index 45dcc3b..7863f60 100644
--- a/README.md
+++ b/README.md
@@ -246,7 +246,30 @@ int_cipher_text, signature = build_string_input_text(plaintext, user_aes_key, se
 
 - `input_text`: A dictionary of the form { "ciphertext": { "value": int[] }, "signature": bytes[] }
 
-### 9. `generate_rsa_keypair()`
+### 9. `build_address_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_address_input_text(plaintext, user_aes_key, sender, contract, func_selector, signing_key)
+```
+
+**Parameters:**
+
+- `plaintext`: The plaintext message.
+- `user_aes_key`: The user's AES key.
+- `sender`: The sender's address.
+- `contract`: The contract address.
+- `func_selector`: The function selector.
+- `signing_key`: The private key used for signing.
+
+**Returns:**
+
+- `input_text`: A dictionary of the form { "ciphertext": { "ct1": int, "ct2": int, "ct3": int }, "signature1": bytes, "signature2": bytes, "signature3": bytes }
+
+### 10. `generate_rsa_keypair()`
 
 **Purpose:** Generates an RSA key pair.
 
@@ -261,7 +284,7 @@ private_key_bytes, public_key_bytes = generate_rsa_keypair()
 - `private_key_bytes`: The serialized private key.
 - `public_key_bytes`: The serialized public key.
 
-### 10. `encrypt_rsa(public_key_bytes, plaintext)`
+### 11. `encrypt_rsa(public_key_bytes, plaintext)`
 
 **Purpose:** Encrypts plaintext using RSA encryption with a provided public key.
 
@@ -280,7 +303,7 @@ ciphertext = encrypt_rsa(public_key_bytes, plaintext)
 
 - `ciphertext`: The encrypted message.
 
-### 11. `decrypt_rsa(private_key_bytes, ciphertext)`
+### 12. `decrypt_rsa(private_key_bytes, ciphertext)`
 
 **Purpose:** Decrypts ciphertext using RSA decryption with a provided private key.
 
@@ -299,7 +322,7 @@ plaintext = decrypt_rsa(private_key_bytes, ciphertext)
 
 - `plaintext`: The decrypted message.
 
-### 12. `decrypt_uint(ciphertext, user_key)`
+### 13. `decrypt_uint(ciphertext, user_key)`
 
 **Purpose:** Decrypts a value stored in a contract using a user key
 
@@ -318,7 +341,7 @@ plaintext = decrypt_uint(ciphertext, user_key)
 
 - `result`: The decrypted value.
 
-### 13. `decrypt_string(ciphertext, user_key)`
+### 14. `decrypt_string(ciphertext, user_key)`
 
 **Purpose:** Decrypts a value stored in a contract using a user key
 
@@ -337,6 +360,25 @@ plaintext = decrypt_string(ciphertext, user_key)
 
 - `result`: The decrypted value.
 
+### 15. `decrypt_address(ciphertext, user_key)`
+
+**Purpose:** Decrypts a value stored in a contract and encrypted using a user key
+
+**Usage:**
+
+```python
+plaintext = decrypt_string(ciphertext, user_key)
+```
+
+**Parameters:**
+
+- `ciphertext`: A dictionary of the form { "ct1": int, "ct2": int, "ct3": int } where each cell holds a portion of the address encrypted
+- `userKey`: The user's AES key.
+
+**Returns:**
+
+- `result`: The decrypted address.
+
 # Utilities (utils.py) Functions
 
 ### 1. `web3_connected(web3)`
diff --git a/coti/crypto_utils.py b/coti/crypto_utils.py
index 435ad85..b3f3ba6 100644
--- a/coti/crypto_utils.py
+++ b/coti/crypto_utils.py
@@ -5,6 +5,7 @@
 from cryptography.hazmat.primitives.asymmetric import padding
 from cryptography.hazmat.primitives.asymmetric import rsa
 from eth_keys import keys
+from web3 import Web3
 
 block_size = AES.block_size
 address_size = 20
@@ -153,6 +154,50 @@ def build_string_input_text(plaintext, user_aes_key, sender, contract, function_
     
     return input_text
 
+def build_address_input_text(plaintext, user_aes_key, sender, contract, function_selector, signing_key):
+    if not Web3.is_address(plaintext):
+        raise ValueError("Plaintext must be a valid address.")
+
+    it_int_1 = build_input_text(
+        int(plaintext[2:18], 16), # bytes 1 - 8
+        user_aes_key,
+        sender,
+        contract,
+        function_selector,
+        signing_key
+    )
+
+    it_int_2 = build_input_text(
+        int(plaintext[18:34], 16), # bytes 9 - 16
+        user_aes_key,
+        sender,
+        contract,
+        function_selector,
+        signing_key
+    )
+
+    it_int_3 = build_input_text(
+        int(plaintext[34:42], 16), # bytes 17 - 20
+        user_aes_key,
+        sender,
+        contract,
+        function_selector,
+        signing_key
+    )
+    
+    input_text = {
+        'ciphertext': {
+            'ct1': it_int_1['ciphertext'],
+            'ct2': it_int_2['ciphertext'],
+            'ct3': it_int_3['ciphertext']
+        },
+        'signature1': it_int_1['signature'],
+        'signature2': it_int_2['signature'],
+        'signature3': it_int_3['signature']
+    }
+    
+    return input_text
+
 
 def decrypt_uint(ciphertext, user_key):
     # Convert ct to bytes (big-endian)
@@ -194,6 +239,28 @@ def decrypt_string(ciphertext, user_key):
     
     return decrypted_string.strip('\0')
 
+def decrypt_address(ciphertext, user_key):
+    if isinstance(ciphertext, list): # format when reading ciphertext from a state variable
+        __ciphertext = ciphertext
+    else: # format when reading ciphertext from an event
+        __ciphertext = list(ciphertext.values())
+
+    addr = '0x'
+    
+    decrypted = decrypt_uint(__ciphertext[0], user_key)
+
+    addr += hex(decrypted)[2:].rjust(16, '0') # 8 bytes is 16 characters
+
+    decrypted = decrypt_uint(__ciphertext[1], user_key)
+
+    addr += hex(decrypted)[2:].rjust(16, '0') # 8 bytes is 16 characters
+
+    decrypted = decrypt_uint(__ciphertext[2], user_key)
+
+    addr += hex(decrypted)[2:].rjust(8, '0') # 4 bytes is 8 characters
+    
+    return Web3.to_checksum_address(addr)
+
 
 def generate_rsa_keypair():
     # Generate RSA key pair