@zkp2p/circuits-circom

circuits-circom

This folder contains the Circom circuits for ZKP2P

Venmo Emails

Venmo uses the same HTML template for its send, receive, request completed sent and request completed received emails. Although each email has different Venmo IDs, at the 4 spaces in the HTML template.

The HTML template:

                <!-- actor name -->
                <a style=3D"color:#0074DE; text-decoration:none" href=3D"ht=
tps://venmo.com/code?user_id=3D<VENMO_ID_1>&actor_id=3D<EMAIL_RECEIVER_VENMO_ID>=
xxxxxx">
                    You
                </a>
                <!-- action -->
                <span>
                    paid
                </span>
              =20
                <!-- recipient name -->
                <a style=3D"color:#0074DE; text-decoration:none"
                   =20
                    href=3D"https://venmo.com/code?user_id=3D<VENMO_ID_2>=
xxxxx&actor_id=3D<EMAIL_RECEIVER_VENMO_ID>">
                   =20
                    Receiver's name
                </a>

Email	VENMO_ID_1	VENMO_ID_2
Venmo Send	Sender/Payer Venmo ID	Receiver/Payee Venmo ID
Venmo Receive	Sender/Payer Venmo ID	Receiver/Payee Venmo ID
Venmo Request Completed Send	Receiver/Payee Venmo ID	Sender/Payer Venmo ID
Venmo Request Completed Receive	Receiver/Payee Venmo ID	Sender/Payer Venmo ID

The protocol ONLY supports the SEND email type

Circuits

Venmo Send Email

Main circuit that onramper generates a proof of payment if offramper fails to generate proof above

• Verifies the DKIM signature (RSA, SHA256)
• Extracts from email, time of payment and amount for the Venmo transaction from the header
• Extract the payee ID and payer ID from the body
• Houses nullifier to prevent replay attacks
• Contains other order information to tie a proof to an order ID to prevent frontrunning

Regex Config	Description
Offramper ID Regex	Extracts the Venmo payee ID from the payment sent email body to ensure the correct offramper is being paid
Onramper ID Regex	Extracts the Venmo payer ID from the payment sent email body to ensure the correct onramper sent the payment. This is to prevent man-in-the-middle attacks if onramper email is revealed to a 3rd party
Send Amount Regex	Extracts $ amount sent from from venmo payment sent email header to ensure its a Send email type and amount is greater than requested
Timestamp Regex	Extracts timestamp from venmo payment sent email header in order to ensure that email payment must be after on-chain intent timestamp
From Email Regex	Extracts from email in venmo payment received email header to ensure that it is sent from [e-mail] and not another Venmo email

Venmo Registration

Main circuit that both onramper and offramper must generate a proof prior to using the protocol

• Verifies the DKIM signature (RSA, SHA256)
• Extracts from email and Venmo amount (restricts to a Send email type of the format: You Paid $X to OFF_RAMPER_NAME) from the header
• Extracts actor ID (my Venmo ID) from the body
• Houses nullifier to prevent replay attacks
• Contains other order information to tie a proof to an order ID to prevent frontrunning

Regex Config	Description
Actor ID Regex	Extracts the Venmo actor ID which is your email
Send Amount Regex	Extracts $ amount sent from from venmo payment sent email header to ensure its a Send email type and amount is greater than requested
From Email Regex	Extracts from email in venmo payment received email header to ensure that it is sent from [e-mail] and not another Venmo email

Regexes

Venmo Payee and Payer ID

The Venmo Payee ID regex is generated using zk-regex which constrains ~330 bytes of HTML to prevent custom injection and index shifting attacks. Regex extracts 2 values: first one after user_id=3D and second one after &actor_id=3D

{
  "parts": [
    {
      "is_public": false,
      "regex_def": "<!-- recipient name -->\r\n"
    },
    {
      "is_public": false,
      "regex_def": "                <a style=3D\"color:#0074DE; text-decoration:none\"\r\n"
    },
    {
      "is_public": false,
      "regex_def": "                   =20\r\n"
    },
    {
      "is_public": false,
      "regex_def": "                    href=3D\"https://venmo.com/code\\?user_id=3D"
    },
    {
      "is_public": true,
      "regex_def": "(0|1|2|3|4|5|6|7|8|9|\r|\n|=)+"
    },
    {
      "is_public": false,
      "regex_def": "&actor_id=3D"
    },
    {
      "is_public": true,
      "regex_def": "(0|1|2|3|4|5|6|7|8|9)+"
    },
    {
      "is_public": false,
      "regex_def": "\">\r\n"
    },
    {
      "is_public": false,
      "regex_def": "                   =20\r\n"
    },
    {
      "is_public": false,
      "regex_def": "                    [^\r\n]+\r\n"
    },
    {
      "is_public": false,
      "regex_def": "                </a>\r\n"
    },
    {
      "is_public": false,
      "regex_def": "               =20\r\n"
    },
    {
      "is_public": false,
      "regex_def": "            </div>\r\n"
    },
    {
      "is_public": false,
      "regex_def": "            <!-- note -->\r\n"
    }
  ]
}

Venmo Actor ID Regex

The Venmo Actor ID regex is generated using zk-regex which constrains ~330 bytes of HTML to prevent custom injection and index shifting attacks. Regex extracts after actor_id=3D. Notice that the regex is exactly the same as above, except the revealed regex string is different

{
    "parts": [
      {
        "is_public": false,
        "regex_def": "<!-- recipient name -->\r\n"
      },
      {
        "is_public": false,
        "regex_def": "                <a style=3D\"color:#0074DE; text-decoration:none\"\r\n"
      },
      {
        "is_public": false,
        "regex_def": "                   =20\r\n"
      },
      {
        "is_public": false,
        "regex_def": "                    href=3D\"https://venmo.com/code\\?user_id=3D"
      },
      {
        "is_public": false,
        "regex_def": "(0|1|2|3|4|5|6|7|8|9|\r|\n|=)+&actor_id=3D"
      },
      {
        "is_public": true,
        "regex_def": "(0|1|2|3|4|5|6|7|8|9)+"
      },
      {
        "is_public": false,
        "regex_def": "\">\r\n                   =20\r\n"
      },
      {
        "is_public": false,
        "regex_def": "                    [^\r\n]+\r\n"
      },
      {
        "is_public": false,
        "regex_def": "                </a>\r\n"
      },
      {
        "is_public": false,
        "regex_def": "               =20\r\n"
      },
      {
        "is_public": false,
        "regex_def": "            </div>\r\n"
      },
      {
        "is_public": false,
        "regex_def": "            <!-- note -->\r\n"
      }
    ]
  }

Venmo Send Amount

The Venmo Send Amount regex is generated using zk-regex which constrains the entire subject line to prevent index shifting attacks. Regex extracts after You paid . Note that this regex limits the user to generate proofs using Send email types. For receive emails, the subject line will be X paid you $Y

{
    "parts": [
        {
            "is_public": false,
            "regex_def": "((\r\n)|^)subject:You paid "
        },
        {
            "is_public": false,
            "regex_def": "[^\r\n]+\\$"
        },
        {
            "is_public": true,
            "regex_def": "(0|1|2|3|4|5|6|7|8|9|\\.|,)+"
        },
        {
            "is_public": false,
            "regex_def": "\r\n"
        }
    ]
}

Regex Template	Description
VenmoPayeeID	Extracts the Venmo payee ID and payer ID from Send email types
VenmoActorId	Extracts the actor ID (my ID) from Send email types
VenmoSendAmount	Extracts the amount from a Send email type
VenmoTimestamp	Extracts the timestamp from Venmo emails
FromRegex	Extracts the from email ([e-mail])

Usage

Generating Regexes

• Go to zk-regex and follow instructions

Compilation

• Create circuit.env cp circuit.env.example circuit.env
• Run yarn compile:TYPE where TYPE is send, receive, registration. This will generate the R1CS SYM and WASM files.

Generate witness

• Copy a SEND eml file into circuits-circom/emls for a given email type. Venmo send emails have the subject line You paid OFFRAMPER_NAME $X. Make sure you are downloading the original email file. For example you can follow the following steps in Gmail. Name your Venmo email venmo_send.eml.
• In circuits-circom directory, run yarn gen-input:TYPE where TYPE is either send, registration. This will generate an input file with the name input_EML_FILE_NAME.json.
• For development purposes, you only need to run up to this step

Run tests

• Inside the circuits-circom directory, first complete the Compilation and generate input steps above for all the circuits. Tests will use the input_EML_FILE_NAME.json, .wasm, and .r1cs files.
• Run yarn test. This will generate witnesses in the wtns files prior to running tests.
• Optionally, only run regex tests by running yarn test test/regexes

Proving Key Generation

• cd into scripts and run cp entropy.env.example entropy.env. Open the file and input your randomness. Entropy is needed to generate the proving key successfully
• For production, run yarn genkey:both:TYPE which will generate both the chunked and nonchunked proving keys for the circuit
• For dev, run yarn genkey:chunked:unsafe for chunked keys or yarn genkey:non-chunked:unsafe, which will skip phase2 contribution and save keygen time (DO NOT USE IN PRODUCTION)

Generating Proofs

• To generate proofs on your local machine, cd into scripts and run CIRCUIT_NAME=YOUR_EMAIL_TYPE ./5_gen_proof.sh
• To generate proofs using RapidSnark serverside, run yarn:genproof:TYPE

Security Assumptions

• Users do not share emails with each other. Treat your email like a private key
• Venmo does not change their email template drastically
• Admin has ability to update verification contracts over time