how-to-encrypt-data-on-chain.md

How to Encrypt Data On-Chain

The following diagram shows a high level workflow to encrypt data on the COTI network, it assumes the following is true:

• User account has been created
• User AES key has been created

Flow to encrypt data on-chain

This is the overview of the process, using the data_on_chain.py example from the Python SDK as a reference:

1. Overall process to send unencrypted value to network, see method basic_clear_encrypt_decrypt
2. First step, method save_clear_value_network_encrypted_in_contract calls a solidity function and sends it a clear value parameter, The network will encrypt that.
   1. This in turn calls setSomeEncryptedValue from the Solidity contract. This is a transitory state to make the clear value available publicly by having it encrypted using the network AES key.
3. Then, Ensure the network block has received clear input correctly using method validate_block_has_tx_input_clear_value. This ensures the relevant block has the clear value sent initially by the user. demonstrating secnario of sending clear value in block but encrypted onchain.
4. Next, in order to get back the value encrypted with the AES key of the user, calling save_network_encrypted_to_user_encrypted_in_contract will call the solidity function of setUserSomeEncryptedValue and by that making it publicly available to read by a view.
   Demonstrating how to save a network encrypted value by the account that called it (the function).
5. Get back encrypted value by account using get_user_encrypted_from_contract that calls a view method getUserSomeEncryptedValue
6. Decrypt value using decrypt_value

Simple basic flow demonstration of sending a clear value to contract, having it encrypted then reading it back making sure it is what was sent.