Silent-Payments

This project is a proof-of-concept of BIP 352: Silent Payments, a method for receiving Bitcoin privately via a static address, without having to communicate directly with the sender.

The repo includes various scenarios to evaluate the correctness and flexibility of Silent Payments, including different input types, taproot combinations, label handling, and more, as outlined in the test_list.json.

Project Structure

silent-payments/
│
├── .gitignore               # Ignore file
├── README.md                # Project documentation
├── requirements.txt         # Dependencies file
└── src/                     # source code
    ├── hardened_keys.py     # hardkeys function gen
    ├── receive.py           # receiver's functions
    ├── schnorr_lib.py       # schnorr-ref-lib
    ├── segwit_addr.py       # bech32m enc/dec reference
    ├── send.py              # sender's functions
    ├── utils.py             # useful functions
    ├── test_legend.json     # .json file for test legend
    ├── test_list.json       # .json file for test list
    ├── test_vectors.json    # .json file for test vectors
    ├── test.ipynb           # Jupyter notebook to easly test
    └── test.py              # main test file

How to install and run code

1. Clone this repository to your local machine:

   git clone https://www.github.com/BitPolito/silent-payments
   cd silent-payments

2. Create a virtual environment (optional but recommended):

   python3 -m venv venv
   source venv/bin/activate 

3. Install dependencies:

   pip install -r requirements.txt

Running the tests

Execute tests running

python3 test.py

and follow the instructions.

Note: Tests must be launched directly from the Test.py script. At the moment, the sender.py and receiver.py files do not support command-line arguments, so it's not possible to run individual tests via the command line. This is something we plan to add in a future version.

Generate a Silent-Payments vanity address

Perform a brute-force search for a vanity address:

python3 vanity.py your_vanity_string

Future works

Silent Payments offer a powerful privacy feature for Bitcoin by allowing recipients to derive unique addresses per transaction without interacting with the sender or publishing any extra data on-chain. However, this design introduces a key technical challenge: scanning the blockchain to detect incoming payments. In a real-world scenario, the recipient must scan every Taproot output to check if it's addressed to them. This process becomes resource-intensive, especially without the help of a full node. So far, our implementation does not connect to a Bitcoin node, but future work will likely require exploring how to integrate one. Relying on a full node would let us maintain an index of Taproot outputs and scan them efficiently, but it also introduces practical concerns — such as node synchronization, bandwidth usage, and managing access to raw blockchain data. According to some estimates, under heavy usage, this could mean ~100 kB per block (up to 450 MB/month), while current conditions suggest a more modest 30–50 MB/month. Understanding whether this scanning can be done independently — or needs lightweight alternatives or external infrastructure — will be crucial to making Silent Payments truly usable at scale.