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September 5, 2024 18:26
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| // Function to generate AccountSalt | |
| import { buildPoseidon } from 'circomlibjs'; | |
| /** | |
| * Attempt at reproducing the account salt generation that zkemail does on the backend at -> | |
| * https://github.com/zkemail/relayer-utils/blob/aefb00fdcfbfde7fced50e5a0b086e5cc2ff64cd/src/cryptos.rs#L198 | |
| * @param email | |
| * @param accountCode | |
| */ | |
| export async function generateAccountSalt(email: string, accountCode: bigint): Promise<string> { | |
| const maxEmailBytes = 256; | |
| // 1. Pad the email address | |
| const paddedEmailBytes = padEmailAddr(email, maxEmailBytes); | |
| // 2. Convert padded email to Poseidon field elements | |
| const emailFields = bytesToFields(paddedEmailBytes); | |
| // 3. Poseidon hash function | |
| const poseidon = await buildPoseidon(); | |
| // 4. Prepare inputs for Poseidon hashing | |
| const inputs = [...emailFields, BigInt(accountCode), BigInt(0)]; | |
| // 5. Compute Poseidon hash to get the AccountSalt | |
| const accountSalt = poseidon(inputs); | |
| return uint8ArrayToHex(accountSalt); | |
| } | |
| function bytesToFields(bytes: Uint8Array): bigint[] { | |
| const chunkSize = 31; | |
| const fieldElements: bigint[] = []; | |
| // Process the bytes in chunks of 31 bytes | |
| for (let i = 0; i < bytes.length; i += chunkSize) { | |
| // Get the current chunk (31 bytes) | |
| const chunk = bytes.slice(i, i + chunkSize); | |
| // Extend the chunk to 32 bytes by padding with zeros | |
| const extended = new Uint8Array(32); | |
| extended.set(chunk); // Copy chunk into the first part of the 32-byte array | |
| // Convert the 32-byte array to a BigInt or field element | |
| const fieldElement = uint8ArrayToBigInt(extended); // Assuming we can treat it as a number here | |
| fieldElements.push(fieldElement); | |
| } | |
| return fieldElements; | |
| } | |
| function uint8ArrayToBigInt(uint8Array: Uint8Array): bigint { | |
| let result = 0n; // Start with a bigint value of 0 | |
| for (const byte of uint8Array) { | |
| // eslint-disable-next-line no-bitwise | |
| result = (result << 8n) + BigInt(byte); // Shift the current value by 8 bits (1 byte) and add the next byte | |
| } | |
| return result; | |
| } | |
| function uint8ArrayToHex(uint8Array: Uint8Array): string { | |
| const noPrepend = Array.from(uint8Array) | |
| .map((byte) => byte.toString(16).padStart(2, '0')) // Convert each byte to hex and pad with '0' if necessary | |
| .join(''); // Join all hex strings into one | |
| return `0x${noPrepend}`; | |
| } | |
| function padEmailAddr(email: string, maxBytes: number): Uint8Array { | |
| const emailBytes = new TextEncoder().encode(email); | |
| const paddedBytes = new Uint8Array(maxBytes); | |
| paddedBytes.set(emailBytes); | |
| return paddedBytes; | |
| } |
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