Enable recovery with a mnemonic seed per nip06

packages/app/src/Util.ts

@@ -7,7 +7,9 @@ import base32Decode from "base32-decode";
 import { HexKey, TaggedRawEvent, u256, EventKind, encodeTLV, NostrPrefix } from "@snort/nostr";
 import * as bip39 from "@scure/bip39";
 import { wordlist } from "@scure/bip39/wordlists/english";
+import { HDKey } from "@scure/bip32";
 
+import { DerivationPath } from "Const";
 import { MetadataCache } from "State/Users";
 
 export const sha256 = (str: string) => {
@@ -102,6 +104,15 @@ export function hexToBech32(hrp: string, hex?: string) {
   }
 }
 
+export function generateBip39Entropy(mnemonic?: string): Uint8Array {
+  try {
+    const mn = mnemonic ?? bip39.generateMnemonic(wordlist);
+    return bip39.mnemonicToEntropy(mn, wordlist);
+  } catch (e) {
+    throw new Error("INVALID MNEMONIC PHRASE");
+  }
+}
+
 /**
  * Convert hex-encoded entropy into mnemonic phrase
  */
@@ -110,6 +121,22 @@ export function hexToMnemonic(hex: string): string {
   return bip39.entropyToMnemonic(bytes, wordlist);
 }
 
+/**
+ * Convert mnemonic phrase into hex-encoded private key
+ * using the derivation path specified in NIP06
+ * @param mnemonic the mnemonic-encoded entropy
+ */
+export function entropyToDerivedKey(entropy: Uint8Array): string {
+  const masterKey = HDKey.fromMasterSeed(entropy);
+  const newKey = masterKey.derive(DerivationPath);
+
+  if (!newKey.privateKey) {
+    throw new Error("INVALID KEY DERIVATION");
+  }
+
+  return secp.utils.bytesToHex(newKey.privateKey);
+}
+
 /**
  * Convert hex pubkey to bech32 link url
  */