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300 lines
12 KiB
Markdown
300 lines
12 KiB
Markdown
---
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title: WAKU-RLN-KEYSTORE
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name: Waku RLN Keystore
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category: Standards Track
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editor: Jimmy Debe <jimmy@status.im>
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contributors:
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- Aaryamann Challani <aaryamann@status.im>
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---
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## Abstract
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This specification describes how RLN, Rate Limit Nullifier,
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credentials are securely stored in a JSON schema.
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## Summary
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A keystore is a construct to store a user’s keys.
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The keys will be encrypted and decrypted based on methods specified in this specification.
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The keystore stores a user's credentials locally and
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uses [32/RLN-V1](/spec/32/) as a spam-prevention mechanism by generating zero-knowledge proofs.
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## Background
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The secure storage of keys is important in peer-to-peer messaging applications.
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A `WAKU-RLN-KEYSTORE` uses zero-knowledge proofs for anonymous rate-limiting for messaging frameworks.
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Generated credentials by a user are encrypted and stored in the keystore to be retrieved over a network.
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With [32/RLN-V1](/spec/32/), sending and receiving
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messages will ensure a message rate for a network is being followed while preserving the anonymity of the message owner.
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### Waku RLN Keystore Format:
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A format example of a keystore used by a [17/WAKU2-RLN-Relay](/spec/17/).
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```js
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const Keystore {
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application: "waku-rln-relay" ,
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appIdentifier: "string",
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version: "string",
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credentials: {
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"membershipHash": {
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crypto: {
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cipher: "string",
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cipherparams: {
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iv: "string",
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},
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ciphertext: "string",
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kdf: "string",
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kdfparams: {
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dklen: integer,
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c: integer,
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prf: "string",
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salt: "string",
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},
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mac: "string",
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}
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}
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}
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}
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```
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## Specification
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The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”,
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“NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC 2119](https://www.ietf.org/rfc/rfc2119.txt).
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The keystore MUST be generated by a cryptographic construction with password verification and decryption.
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Keystore modules MUST include metadata, key derivation function, checksum, cipher, and a membership hash.
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### Metadata:
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Information about the keystore SHOULD be stored in the metadata.
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The declaration of `application`, `version`, and `appIdentifier` COULD occur in the metadata.
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- `application` : current application, MUST be a string
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- `version` : application version, MUST be a string, SHOULD follow semantic versioning
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- `appIdentifier`: application identifier, MUST be a string
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### Credentials:
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After RLN credentials are generated, it MUST be stored in a JSON schema.
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The Waku RLN credentials MUST consist of a `membershipHash` and `WakuCredential`.
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The `membershipHash` will be an identity hash of the user.
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The `WakuCredential` will store to encryption portion of the keystore.
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There COULD be multiple credentials stored in a keystore, categorized by the `membershipHash`.
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Each contruct MUST include the keypair:
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> key: [`membershipHash`]: pair: [`WakuCredential`]
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#### membershipHash
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The `membershipHash` SHOULD be generated by user's participating in a membership group,
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as decribed in [32/RLN-V1](/spec/32/).
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Each user SHOULD register to the group with an `identity_commitment` stored in a Merkle tree.
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A cryptographic hash function that SHOULD be used to generate the `membershipHash` is [SHA256](https://www.rfc-editor.org/rfc/rfc4634.txt),
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other hash functions MAY be used.
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The hash function that is used,
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SHOULD be mentioned in the `verison` attribute.
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To generate the `membershipHash`,
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the `treeIndex`, `membershipContract`, `chainId` and `identityCredential` attributes SHOULD be used to create a hexadecimal string.
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- it MUST NOT already exist in the keystore.
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##### `treeIndex`
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After a user registers to a group,
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a `treeIndex` value of the position in the Merkle tree SHOULD be returned.
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- it MUST be a Merkle tree data structure filled with `identity_commitment` from user registrations.
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- it MUST be a hexadecimal string
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##### `membershipContract`
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For decentralized membership registrations,
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the `membershipContract` SHOULD be a `contractAddress` from a public blockchain using smart contracts.
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- it MUST be a string.
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##### `chainId`
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It uniquely defines the chain upon which the registration has occurred.
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The `chainId` SHOULD be the blockchain identifier used for `membershipcontract`,
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as described in [EIP155](https://eips.ethereum.org/EIPS/eip-155).
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- it MUST be a string
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##### `identityCredential`
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The `identityCredential` MUST be derived after a succussful decryption of the keystore.
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The `identityCredential` MUST be constructed with the `identity_secret`, `identity_secret_hash`, `identity_commitment` values.
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- it MUST be a hash of `identity_commitment` stored in a Merkle tree.
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- it MUST be a string.
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###### `identity_secret`
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The `identity_secret` MUST be constructed with `identity_nullifier` + `identity_trapdoor` values.
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- `identity_nullifier` : Random 32 byte value
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- `identity_trapdoor` : Random 32 byte value
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###### `identity_secret_hash`
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Used to derive the `identity_commitment` of the user, and
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as a private input for zero-knowledge proof generation.
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- it MUST be created with `identity_secret` as a parameter for the hash function.
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- This secret hash SHOULD be kept private by the user.
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###### `identity_commitment`
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- it SHOULD be created with `identity_secret_hash` by using the hash function Poseidon,
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as described in [Poseidon Paper](https://eprint.iacr.org/2019/458.pdf).
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- it MUST be used by a user for group registering.
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#### WakuCredential
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The `WakuCredential` will store values used for encrypting and decrypting user's keystores.
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- it MUST be used for password verification.
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- it MUST follow [EIP-2335](https://eips.ethereum.org/EIPS/eip-2335)
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- it SHOULD use [SHA256](https://www.rfc-editor.org/rfc/rfc4634.txt) as the hash function
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#### KDF
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The password-based encryption used SHOULD be KDF, key derivation function,
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to produce a derived key from a password and other parameters.
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The keystore COULD use PBKDF2 password-based encryption,
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as described in [RFC 2898](https://www.ietf.org/rfc/rfc2898.txt).
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A `WakuCredential` object MUST include:
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| Name | Description |
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|----|-----|
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| password | used to encrypt keystore and decryption key |
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| secret | key to be encrypted |
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| pubKey | public key |
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| path | HD, hardened derivation, path used to generate the secret |
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| checksum | hash function |
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| cipher | cipher function |
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```js
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crypto: {
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cipher: "string" // The cipher function
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cipherparams: {
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iv: "string" // The cipher parameters
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},
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ciphertext: "string" // The cipher message,
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kdf: "string" // KDF Function,
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kdfparams: {
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param: integer // Salt value and iteration count,
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dklen: integer // Length in octets of derived key, MUST be positive integer,
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c: "string" // Iteration count, MUST be positive integer,
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prf: "string" // Underlying pseudorandom function,
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salt: "string" // Produces a large set of keys based on the password
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},
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mac: "string" // Checksum
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}
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```
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#### Decryption
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The keystore SHOULD decrypt a user's credentials using a password and the `membershipHash`,
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using PBKDF2 that returns the `decryptionKey` key.
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The decryption key is used to verify the keystore is correct.
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- To generate the `decryptionKey`, it MUST be constructed from a password and KDF,
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as desrcibed in [ERC-2335: BLS12-381 Keystore](https://eips.ethereum.org/EIPS/eip-2335).
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- The `decryptionKey`, is derived from the cipher function and
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cipher parameters described in the KDF used in the keystore.
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### Test Vectors
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RLN uses Poseidon hash algorithm to generate the `identityCredential`,
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as described in [Poseidon Paper](https://eprint.iacr.org/2019/458.pdf).
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The keystore hash algorithm used is [SHA256](https://www.rfc-editor.org/rfc/rfc4634.txt).
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#### Input:
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- `application`: "waku-rln-relay"
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- `appIdentifier`: "01234567890abcdef"
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- `version`: "0.2"
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- `hashFunction`: "poseidonHash"
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- `password`: "sup3rsecure"
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```js
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identityCredential = {
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IDTrapdoor: [
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211, 23, 66, 42, 179, 130, 131, 111, 201, 205, 244, 34, 27, 238, 244,
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216, 131, 240, 188, 45, 193, 172, 4, 168, 225, 225, 43, 197, 114, 176,
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126, 9,
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],
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IDNullifier: [
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238, 168, 239, 65, 73, 63, 105, 19, 132, 62, 213, 205, 191, 255, 209, 9,
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178, 155, 239, 201, 131, 125, 233, 136, 246, 217, 9, 237, 55, 89, 81,
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42,
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],
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IDSecretHash: [
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150, 54, 194, 28, 18, 216, 138, 253, 95, 139, 120, 109, 98, 129, 146,
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101, 41, 194, 36, 36, 96, 152, 152, 89, 151, 160, 118, 15, 222, 124,
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187, 4,
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],
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IDCommitment: [
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112, 216, 27, 89, 188, 135, 203, 19, 168, 211, 117, 13, 231, 135, 229,
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58, 94, 20, 246, 8, 33, 65, 238, 37, 112, 97, 65, 241, 255, 93, 171, 15,
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],
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}
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membership = {
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chainId: "0xAA36A7",
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treeIndex: 8,
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address: "0x8e1F3742B987d8BA376c0CBbD7357fE1F003ED71",
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}
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```
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#### Output:
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```js
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application: "waku-rln-relay",
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appIdentifier: "01234567890abcdef",
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version: "0.2",
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credentials: {
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"9DB2B4718A97485B9F70F68D1CC19F4E10F0B4CE943418838E94956CB8E57548": {
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crypto: {
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cipher: "aes-128-ctr",
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cipherparams: {
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iv: "fd6b39eb71d44c59f6bf5ff3d8945c80",
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},
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ciphertext: "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",
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kdf: "pbkdf2",
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kdfparams: {
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dklen: 32,
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c: 1000000,
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prf: "hmac-sha256",
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salt: "60f0aa92fbf63a8356dfdbed2ab18058",
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},
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mac: "51a227ac6db7f2797c63925880b3db664e034231a4c68daa919ab42d8df38bc6",
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},
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}
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```
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## Security Considerations
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### 1.) Add a Password
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An attacker can identify which credential belongs to a combination of `chainId` and
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`contractAddress` pair by brute forcing the `treeIndex` iteratively to find a hash match.
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The RECOMMENDED solution is to add a password to the construction of `membershipHash` to prevent this attack.
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The RECOMMENDED `membershipHash` Construction:
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- `membershipHash` SHOULD be constructed with `treeIndex`, `membershipContract`, `identityCredential`, `membershipPassword`
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- `membershipPassword` : a new password created to private attacks compromising keystore credentials.
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- The user MUST store the `membershipPassword` privately.
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## Copyright
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Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).
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## References
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1. [32/RLN-V1](/spec/32/)
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2. [17/WAKU2-RLN-RELAY](/spec/17/)
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3. [SHA256](https://www.rfc-editor.org/rfc/rfc4634.txt)
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4. [EIP155](https://eips.ethereum.org/EIPS/eip-155)
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5. [Poseidon Paper](https://eprint.iacr.org/2019/458.pdf)
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6. [EIP-2335](https://eips.ethereum.org/EIPS/eip-2335)
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7. [RFC 2898](https://www.ietf.org/rfc/rfc2898.txt)
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8. [ERC-2335: BLS12-381 Keystore](https://eips.ethereum.org/EIPS/eip-2335)
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