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118 lines
5.5 KiB
Markdown
118 lines
5.5 KiB
Markdown
NIP-XX
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Nostr-Specific Deterministic Private Key Generation from Ethereum Wallet Signature
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--
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`draft` `optional` `author:0xc0de4c0ffee` `author:sshmatrix`
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## Abstract
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This specification provides an optional method for Nostr clients to generate deterministic private keys from Ethereum wallet signatures.
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## Terminology
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### a) `username`
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Username can be either of the following:
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`username` or `user@domain.eth.limo` or `domain.eth.limo` or `sub.domain.eth.limo`, where,
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- `username` is a [NIP-02](https://github.com/nostr-protocol/nips/blob/master/05.md) compatible name,
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- `name@domain.eth.limo` is a [NIP-05](https://github.com/nostr-protocol/nips/blob/master/05.md) compatible name,
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- `domain.eth.limo` is [NIP-05](https://github.com/nostr-protocol/nips/blob/master/05.md) equivalent of
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`_@domain.eth.limo`,
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- `sub.domain.eth.limo` is [NIP-05](https://github.com/nostr-protocol/nips/blob/master/05.md) equivalent of
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`_@sub.domain.eth.limo`.
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> Note : `sub@domain.eth.limo` and `sub.domain.eth.limo` are NOT same ID as their signatures will be different.
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### b) `password`
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Password is optional string value used in HKDF salt,
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```js
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let password = "horse staple battery"
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let salt = await sha256(`eip155:${chainId}:${username}:${password?password:""}:${signature.slice(68)}`);
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```
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### c) `message`
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```js
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let message = `Login to Nostr as ${username}\n\nImportant: Please verify the integrity and authenticity of your Nostr client before signing this message.\n${info}`
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```
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### d) `signature`
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Deterministic signature from connected wallet. Signatures are 65 bytes long, `bytes1(v)+bytes32(r)+bytes32(s)`.
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```js
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let signature = wallet.signMessage(message);
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```
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### e) `HKDF`
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HKDF-SHA-256 is used to derive 42 bytes long hash key.
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`hkdf(sha256, inputKey, salt, info, dkLen = 42)`
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- `Input key` is SHA-256 hash of signature bytes.
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```js
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let inputKey = await sha256(hexToBytes(signature.slice(2)));
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```
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- `Salt` is SHA-256 hash of following identifier string. `signature.slice(68)` is hex `s` value of signature, last 32 bytes.
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```js
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let salt = await sha256(`eip155:${chainId}:${username}:${password?password:""}:${signature.slice(68)}`);
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```
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- `Info` is string with following format.
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```js
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let info = `eip155:${chainId}:${username}:${address}`;
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```
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- `Derived Key Length` is set to 42. FIPS 186/4 B.4.1 require hash length to be >=n+8 where, n is length of final private key. (42 >= 32 + 8)
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```js
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let dkLen = 42;
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```
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- `hashToPrivateKey` function is FIPS 186-4 B.4.1 implementation to convert derived hash keys from `HKDF`to valid `secp256k1` private keys. This function is implemented in js `@noble/secp256k1` as `hashToPrivateKey`.
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```js
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let hashKey = hkdf(sha256, inputKey, salt, info, dkLen=42);
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let privKey = secp256k1.utils.hashToPrivateKey(hashKey);
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let pubKey = secp256k1.schnorr.getPublicKey(privKey);
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```
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## Implementation Requirements
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- Connected Ethereum Wallet signer MUST be EIP191 and RFC6979 compatible.
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- The message MUST be string formatted as `Login to Nostr as ${username}\n\nImportant: Please verify the integrity and authenticity of your Nostr client before signing this message.\n${info}`.
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- HKDF input key MUST be generated as the SHA-256 hash of 65 bytes signature.
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- HKDF salt MUST be generated as SHA-256 hash of string `eip155:${chainID}:${username}:${password?password:""}:${signature.slice(68)}`.
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- HKDF derived key length MUST be 42.
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- HKDF info MUST be string formatted as `eip155:${chainId}:${username}:${address}`
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## JS Example
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```js
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const secp256k1 = require('@noble/secp256k1');
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const {hexToBytes, bytesToHex} = require('@noble/hashes/utils');
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const {hkdf} = require('@noble/hashes/hkdf');
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const {sha256} = require('@noble/hashes/sha256');
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// const wallet = // connected ethereum wallet with ethers.js
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let username = "me@domain.eth.limo"
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let chainId = wallet.getChainId(); // get chainid from connected wallet
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let address = wallet.getAddress(); // get address from wallet
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let info = `eip155:${chainId}:${username}:${address}`;
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let message = `Login to Nostr as ${username}\n\nImportant: Please verify the integrity and authenticity of your Nostr client before signing this message.\n${info}`
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let signature = wallet.signMessage(message); // request signature from wallet
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let password = "horse staple battery"
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let inputKey = await sha256(hexToBytes(signature.slice(2))); //skip "0x"
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let salt = await sha256(`eip155:${chainId}:${username}:${password?password:""}:${signature.slice(68)}`);
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let dkLen = 42;
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let hashKey = await hkdf(sha256, inputKey, salt, info, dkLen);
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let privKey = secp256k1.utils.hashToPrivateKey(hashKey);
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let pubKey = secp256k1.schnorr.getPublicKey(privKey);
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```
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## Security Considerations
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- Users should always verify the integrity and authenticity of the Nostr client before signing the message.
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- Users should ensure that they only input their Nostr username and password in trusted and secure clients.
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- Implementing clients should ensure ~~..private key/security~~
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## References:
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- [RFC6979: Deterministic Usage of the DSA and ECDSA](https://datatracker.ietf.org/doc/html/rfc6979)
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- [RFC5869: HKDF (HMAC-based Extract-and-Expand Key Derivation Function)](https://datatracker.ietf.org/doc/html/rfc5869)
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- [Digital Signature Standard (DSS), FIPS 186-4 B.4.1](https://csrc.nist.gov/publications/detail/fips/186/4/final)
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- [ERC191: Signed Data Standard](https://eips.ethereum.org/EIPS/eip-191)
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- [EIP155: Simple replay attack protection](https://eips.ethereum.org/EIPS/eip-155)
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- [@noble/hashes](https://github.com/paulmillr/noble-hashes)
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- [@noble/secp256k1](https://github.com/paulmillr/noble-secp256k1) |