feat: implements convert mnemonic to privateKey

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## Unreleased
 
 TBD
+- [\#64](https://github.com/medibloc/panacea-js/pull/64) feat: implements convert mnemonic to privateKey of Secp256k1
+
 
 ## [v2.0.1](https://github.com/medibloc/panacea-js/releases/tag/v2.0.1) - 2022-06-03
 

docs/examples.md

@@ -144,3 +144,18 @@ assertIsDeliverTxSuccess(result);
 const didDocumentWithSeq = await client.getPanaceaClient().getDid(didDocument.id);
 console.log(didDocumentWithSeq);
 ```
+
+## Convert mnemonic to Secp256k1 privateKey
+
+```ts
+import {Secp256k1 as CryptoSecp256k1, stringToPath, sha256} from "@cosmjs/crypto";
+import {panacead} from "../testutils";
+import {TextEncoder} from "util";
+import {Secp256k1} from "./secp256k1";
+
+const mnemonic = "bulb rail ...";
+const hdPath = stringToPath("m/44'/371'/0'/0/0");
+
+const privateKey = await Secp256k1.parseMnemonicToPrivateKey(mnemonic, hdPath);
+const {pubkey} = await CryptoSecp256k1.makeKeypair(privateKey);
+```

src/crypto/secp256k1.spec.ts

@@ -0,0 +1,19 @@
+import {Secp256k1 as CryptoSecp256k1, stringToPath, sha256} from "@cosmjs/crypto";
+import {panacead} from "../testutils";
+import {TextEncoder} from "util";
+import {Secp256k1} from "./secp256k1";
+
+describe("Secp256k1", () => {
+
+    it("parseMnemonicToPrivateKey", async () => {
+        const body = "testBody";
+        const hashedBody = sha256(new TextEncoder().encode(body));
+        const hdPath = stringToPath("m/44'/371'/0'/0/0");
+
+        const privateKey = await Secp256k1.parseMnemonicToPrivateKey(panacead.mnemonic, hdPath);
+        const {pubkey} = await CryptoSecp256k1.makeKeypair(privateKey);
+
+        const signature = await CryptoSecp256k1.createSignature(hashedBody, privateKey)
+        expect(CryptoSecp256k1.verifySignature(signature, hashedBody, pubkey)).toBeTruthy()
+    });
+});

src/crypto/secp256k1.ts

@@ -1,20 +1,27 @@
 import ecc from "secp256k1";
-import { randomBytes } from "crypto";
+import {randomBytes} from "crypto";
+import {Bip39, EnglishMnemonic, Slip10, Slip10Curve, Slip10RawIndex} from "@cosmjs/crypto"
 
 export class Secp256k1 {
-  static generatePrivateKey(): Uint8Array {
-    let privKey
-    do {
-      privKey = randomBytes(32)
-    } while (!ecc.privateKeyVerify(privKey));
-    return privKey;
-  }
+    static generatePrivateKey(): Uint8Array {
+        let privKey
+        do {
+            privKey = randomBytes(32)
+        } while (!ecc.privateKeyVerify(privKey));
+        return privKey;
+    }
 
-  static getPublicKeyCompressed(privKey: Uint8Array): Uint8Array {
-    return ecc.publicKeyCreate(privKey);
-  }
+    static getPublicKeyCompressed(privKey: Uint8Array): Uint8Array {
+        return ecc.publicKeyCreate(privKey);
+    }
 
-  static sign(data32: Uint8Array, privKey: Uint8Array): Uint8Array {
-    return ecc.ecdsaSign(data32, privKey).signature;
-  }
+    static sign(data32: Uint8Array, privKey: Uint8Array): Uint8Array {
+        return ecc.ecdsaSign(data32, privKey).signature;
+    }
+
+    static async parseMnemonicToPrivateKey(mnemonic: string, hdPath: readonly Slip10RawIndex[]): Promise<Uint8Array> {
+        const mnemonicChecked = new EnglishMnemonic(mnemonic)
+        const seed = await Bip39.mnemonicToSeed(mnemonicChecked, "")
+        return Slip10.derivePath(Slip10Curve.Secp256k1, seed, hdPath).privkey
+    }
 }