Update READMEs

README.md

@@ -4,7 +4,7 @@ One issue with existing applications on Ethereum is that all users who execute t
 Our ether email-auth SDK solves this issue: it allows users to execute any transaction on-chain simply by sending an email.
 
 Using the SDK, a developer can build a smart contract with the following features without new ZKP circuits.
-1. (Authorization) The contract can authorize any message in the Subject of the email that the user sends with a DKIM signature generated by an email provider, e.g., Gmail. 
+1. (Authorization) The contract can authorize any message in the email body that the user sends with a DKIM signature generated by an email provider, e.g., Gmail. 
 2. (Authentication) The contract can authenticate that the given Ethereum address corresponds to the email address in the From field of the email.
 3. (Privacy) No on-chain information reveals the user's email address itself. In other words, any adversary who learns only public data cannot estimate the corresponding email address from the Ethereum address.
 
@@ -19,10 +19,10 @@ Using the ether email-auth SDK, we construct a library and tools for any smart a
 In addition to a user and a smart contract employing our SDK, there is a permissionless server called Relayer.
 The Relayer connects the off-chain world, where the users are, with the on-chain world, where the contracts reside, without compromising security.
 Specifically, the user, the Relayer, and the contract collaborate as follows:
-1. (Off-chain) The user sends the Relayer an email containing a message to the contract in the Subject.
-2. (Off-chain) The Relayer generates **an email-auth message for the given email, consisting of data about the Subject, an Ethereum address corresponding to the user's email address, a ZK proof of the email, and so on**.
+1. (Off-chain) The user sends the Relayer an email containing a message called command.
+2. (Off-chain) The Relayer generates **an email-auth message for the given email, consisting of data about the command, an Ethereum address corresponding to the user's email address, a ZK proof of the email, and so on**.
 3. (Off-chain -> On-chain) The Relayer broadcasts an Ethereum transaction to call the contract with the email-auth message.
-4. (On-chain) After verifying the given email-auth message, the contract executes application-specific logic depending on the message in the Subject and the user's Ethereum address.
+4. (On-chain) After verifying the given email-auth message, the contract executes application-specific logic according to the command in that message for an Ethereum account derived from the user's email address.
 5. (On-chain -> Off-chain) The Relayer sends the user an email to report the execution result of the contract.
 
 ![Architecture Flow](./docs/images/architecture-flow.png)
@@ -35,35 +35,35 @@ That CREATE2 salt is called account salt, which is published on-chain.
 **As long as the account code is hidden, no adversary can learn the user's email address from on-chain data.** 
 
 ### Invitation Code
-An invitation code is a hex string of the account code along with a prefix, contained in any field of the email header to be inherited by its reply, e.g., Subject.
+An invitation code is a hex string of the account code along with a prefix, contained in the email body and inherited by the user's reply.
 By confirming that a user sends an email with the invitation code, the contract can ensure that the account code is available to that user. 
 It ensures the user’s liveness even when a malicious relayer or another user generates the user's account code because it prevents them from withholding the account code. 
 **It suggests that the contract must check if the given email sent by the user contains the invitation code before confirming that user’s account for the first time.**
 
 Notably, the email-auth message, which represents data in the user's email along with its ZK proof, has a boolean field `isCodeExist` such that the value is true if the invitation code is in the email.
-However, the Subject message in the email-auth message masks characters for the invitation code.
+However, a command in the email-auth message masks characters for the invitation code.
 **Consequently, no information beyond the existence of the invitation code is disclosed.**
 
-### Subject Template
-A subject template defines the expected format of the message in the Subject for each application.
-**It allows developers to constrain that message to be in the application-specific format without new ZKP circuits.**
+### Command Template
+Each application defines expected formats for a command in the email body as command templates.
+**To define the command templates, a developer does not need to write any ZKP circuits.**
 
-Specifically, the subject template is an array of strings, each of which has some fixed strings without space and the following variable parts:
+Specifically, the command template is an array of strings, each of which has some fixed strings without space and the following variable parts:
 - `"{string}"`: a string. Its Solidity type is `string`.
 - `"{uint}"`: a decimal string of the unsigned integer. Its Solidity type is `uint256`.
 - `"{int}"`: a decimal string of the signed integer. Its Solidity type is `int256`.
 - `"{decimals}"`: a decimal string of the decimals. Its Solidity type is `uint256`. Its decimal size is fixed to 18. E.g., “2.7” ⇒ `abi.encode(2.7 * (10**18))`.
-- `"{ethAddr}"`: a hex string of the Ethereum address. Its Solidity type is `address`. Its value MUST satisfy the checksum of the Ethereum address.
+- `"{ethAddr}"`: a hex string of the Ethereum address. Its Solidity type is `address`. Its value MUST be either 0x+lowercase, 0x+uppercase, or 0x+checksumed addresses.
 
 ## Package Components
 There are four significant packages in this repo:
 ### `circuits` Package
-It has a main circom circuit for verifying the email along with its DKIM signature, revealing a Subject message that masks an email address and an invitation code, and deriving an account salt from the email address in the From field and the given account code, which should match with the invitation code if it exists in the email.
-The circuit is agnostic to application contexts such as subject templates.
+It has a main circom circuit for verifying the email along with its DKIM signature, revealing a command message that masks an email address and an invitation code, and deriving an account salt from the email address in the From field and the given account code, which should match with the invitation code if it exists in the email.
+The circuit is agnostic to application specifications such as command templates.
 **Therefore, a developer does not need to make new circuits.**
 
-In a nutshell, our circuit 1) verifies the given RSA signature for the given email header and the RSA public key, 2) exposes the string in the Subject field except for the invitation code and the email address that appears in the Subject, and 3) computes the account salt derived from the email address in the From field and the given account code, which must be the same as the invitation code if it exists.
-In this way, it allows our on-chain verifier to authenticate the email sender and authorize the message in the Subject while protecting privacy.
+In a nutshell, our circuit 1) verifies the given RSA signature for the given email header and the RSA public key, 2) exposes a substring between predefined prefix and suffix as a command from the email body while masking the invitation code and email address, and 3) computes the account salt derived from the email address in the From field and the given account code, which must match the invitation code, if present.
+This allows our on-chain verifier to authenticate the email sender and authorize the command in the email body while protecting privacy.
 
 For detailed setup instructions, see [here](./packages/circuits/README.md).
 
@@ -81,11 +81,11 @@ If you use the common trusted custodians for all users, you can deploy a new DKI
 If each user should be able to modify the registered public keys, a new DKIM registry contract needs to be deployed for each user.
 
 The email-auth contract in `EmailAuth.sol` is a contract for each email user.
-Its contract Ethereum address is derived from 1) its initial owner address, 2) an address of a controller contract that can define the supported subject templates and 3) the account salt, i.e., the hash of the user's email address and one account code held by the user, through CREATE2.
+Its contract Ethereum address is derived from 1) its initial owner address, 2) an address of a controller contract that can define the supported command templates and 3) the account salt, i.e., the hash of the user's email address and one account code held by the user, through CREATE2.
 It provides a function `authEmail` to verify the email-auth message by calling the verifier and the DKIM registry contracts.
 
 Your application contract can employ those contracts in the following manner:
-1. For a new email user, the application contract deploys (a proxy of) the email-auth contract. Subsequently, the application contract sets the addresses of the verifier and the DKIM registry contracts and some subject templates for your application to the email-auth contract. Here, the email-auth contract registers the application contract as a controller contract that has permissions to modify the subject templates.
+1. For a new email user, the application contract deploys (a proxy of) the email-auth contract. Subsequently, the application contract sets the addresses of the verifier and the DKIM registry contracts and some command templates for your application to the email-auth contract. Here, the email-auth contract registers the application contract as a controller contract that has permissions to modify the command templates.
 2. Given a new email-auth message from the email user, the application contract calls the `authEmail` function in the email-auth contract for that user. If it returns no error, the application contract can execute any processes based on the message in the email-auth message.
 
 For detailed setup instructions, see [here](./packages/contracts/README.md).
@@ -108,7 +108,7 @@ Our SDK only performs the verification of the email-auth message.
 
 Here, we present a list of security notes that you should check.
 - As described in the Subsection of "Invitation Code", for each email user, your application contract must ensure that the value of `isCodeExist` in the first email-auth message is true.
-- The application contract can configure multiple subject templates for the same email-auth contract. However, the Relayer can choose any of the configured templates, as long as the message in the Subject matches with the chosen template. For example, if there are two templates "Send {decimals} {string}" and "Send {string}", the message "Send 1.23 ETH" matches with both templates. We recommend defining the subject templates without such ambiguities.
+- The application contract can configure multiple command templates for the same email-auth contract. However, the Relayer can choose any of the configured templates, as long as the message in the command matches with the chosen template. For example, if there are two templates "Send {decimals} {string}" and "Send {string}", the message "Send 1.23 ETH" matches with both templates. We recommend defining the command templates without such ambiguities.
 - To protect the privacy of the users' email addresses, you should carefully design not only the contracts but also the Relayer server, which stores the users' account codes. For example, an adversary can breach that privacy by exploiting an API provided by the Relayer that returns the Ethereum address for the given email address and its stored account code. Additionally, if any Relayer's API returns an error when no account code is stored for the given email address, the adversary can learn which email addresses are registered.
 
 ## Application: Email-based Account Recovery
@@ -147,16 +147,16 @@ Our SDK cannot ensure security and privacy in the entire process without your ca
 Specifically, you can integrate the email-based account recovery into your smart accounts in the following steps.
 1. (Contracts 1/6) First, you build a new controller contract with imports of the `EmailAccountRecovery` abstract contract in `EmailAccountRecovery.sol`. Your Solidity compiler will require you to implement the following seven functions: 
 `isActivated`,
-`acceptanceSubjectTemplates`, `recoverySubjectTemplates`, `extractRecoveredAccountFromAcceptanceSubject`, `extractRecoveredAccountFromRecoverySubject`, `acceptGuardian`, `processRecovery`, and `completeRecovery`.
-2. (Contracts 2/6) You define expected subject templates for two types of emails sent from guardians, one for accepting the role of the guardian, and the other for confirming the account recovery. You can implement the former and latter subject templates in the `acceptanceSubjectTemplates` and `recoverySubjectTemplates` functions, respectively. This is an example of the subject templates:
-    - Template in `acceptanceSubjectTemplates`: `"Accept guardian request for {ethAddr}"`, where the value of `"{ethAddr}"` represents the account address.
-    - Template in `recoverySubjectTemplates`: `"Set the new signer of {ethAddr} to {ethAddr}"`, where the values of the first and second `"{ethAddr}"`, respectively, represent the account address and the new owner address.
-3. (Contracts 3/6) You also define how to extract an account address to be recovered from the subject parameters for the templates in `acceptanceSubjectTemplates` and `recoverySubjectTemplates`, respectively.
+`acceptanceCommandTemplates`, `recoveryCommandTemplates`, `extractRecoveredAccountFromAcceptanceCommand`, `extractRecoveredAccountFromRecoveryCommand`, `acceptGuardian`, `processRecovery`, and `completeRecovery`.
+2. (Contracts 2/6) You define expected command templates for two types of emails sent from guardians, one for accepting the role of the guardian, and the other for confirming the account recovery. You can implement the former and latter command templates in the `acceptanceCommandTemplates` and `recoveryCommandTemplates` functions, respectively. This is an example of the command templates:
+    - Template in `acceptanceCommandTemplates`: `"Accept guardian request for {ethAddr}"`, where the value of `"{ethAddr}"` represents the account address.
+    - Template in `recoveryCommandTemplates`: `"Set the new signer of {ethAddr} to {ethAddr}"`, where the values of the first and second `"{ethAddr}"`, respectively, represent the account address and the new owner address.
+3. (Contracts 3/6) You also define how to extract an account address to be recovered from the command parameters for the templates in `acceptanceCommandTemplates` and `recoveryCommandTemplates`, respectively.
 3. (Contracts 4/6) Before implementing the remaining functions in `EmailAccountRecovery`, you implement a requesting function into the controller that allows the account owner to request a guardian, which is expected to be called by the account owner directly. Our SDK **does not** specify any interface or implementation of this function. For example, the function can simply take as input a new guardian's email-auth contract address computed by CREATE2, and store it as a guardian candidate. If you want to set a timelock for each guardian, the requesting function can additionally take the timelock length as input.
-4. (Contracts 5/6) You implement the `acceptGuardian` and `processRecovery` functions into the controller. These two functions are, respectively, called by the controller itself after verifying the email-auth messages for accepting a guardian and processing a recovery. Each of them takes as input the guardian's email-auth contract address, an index of the chosen subject template, the values for the variable parts of the message in the Subject, and the email nullifier. You can assume these arguments are already verified. For example, the `acceptGuardian` function stores the given guardian's address as the confirmed guardian, and the `processRecovery` function stores the given new owner's address or sets a timelock.
+4. (Contracts 5/6) You implement the `acceptGuardian` and `processRecovery` functions into the controller. These two functions are, respectively, called by the controller itself after verifying the email-auth messages for accepting a guardian and processing a recovery. Each of them takes as input the guardian's email-auth contract address, an index of the chosen command template, the values for the variable parts of the message in the command, and the email nullifier. You can assume these arguments are already verified. For example, the `acceptGuardian` function stores the given guardian's address as the confirmed guardian, and the `processRecovery` function stores the given new owner's address or sets a timelock.
 5. (Contracts 6/6) You finally implement the `completeRecovery` function into the controller. It should rotate the owner's address in the smart account if some required conditions hold. This function can be called by anyone, but is assumed to be called by the Relayer and can take as input arbitrary bytes.
-6. (Frontend 1/3) Next, you build a frontend for the account recovery. You prepare a page where the account owner configures guardians. It requests the account owner to input the account address (`account_eth_addr`) and the guardian's email address  (`guardian_email_addr`), generates a random account code (`account_code`), constructs an expected subject (`subject`) for the subject template whose index is `template_idx` in the output of the `acceptanceSubjectTemplates()` function. It then requests the account owner to call the requesting function in the controller contract. After that, it calls the Relayer's `acceptanceRequest` API with `guardian_email_addr`, `account_code`, `template_idx`, and the address of the controller contract `controller_eth_addr`.
-7. (Frontend 2/3) You also prepare a page where the account owner requests guardians to recover the account. It requests the account owner to input the account address (`account_eth_addr`) and the guardian's email address (`guardian_email_addr`), and constructs an expected subject (`subject`) for the subject template whose index is `template_idx` in the output of the `recoverySubjectTemplates()` function. It calls the Relayer's `recoveryRequest` API with those data and `controller_eth_addr`.
+6. (Frontend 1/3) Next, you build a frontend for the account recovery. You prepare a page where the account owner configures guardians. It requests the account owner to input the account address (`account_eth_addr`) and the guardian's email address  (`guardian_email_addr`), generates a random account code (`account_code`), constructs an expected command (`command`) for the command template whose index is `template_idx` in the output of the `acceptanceCommandTemplates()` function. It then requests the account owner to call the requesting function in the controller contract. After that, it calls the Relayer's `acceptanceRequest` API with `guardian_email_addr`, `account_code`, `template_idx`, and the address of the controller contract `controller_eth_addr`.
+7. (Frontend 2/3) You also prepare a page where the account owner requests guardians to recover the account. It requests the account owner to input the account address (`account_eth_addr`) and the guardian's email address (`guardian_email_addr`), and constructs an expected command (`command`) for the command template whose index is `template_idx` in the output of the `recoveryCommandTemplates()` function. It calls the Relayer's `recoveryRequest` API with those data and `controller_eth_addr`.
 8. (Frontend 3/3) It simulates off-chain if the `completeRecovery` function in the smart account will return no error at regular time intervals. When it stands, the frontend calls the Relayer's `completeRequest` API with sending `account_eth_addr`, `controller_eth_addr`, and a calldata for the `completeRecovery` function `complete_calldata`.  
 
 We show some important points to implement the email-based account recovery for your smart accounts securely.