Fix string values in zk (MystenLabs#14265)

## Description 

Describe the changes or additions included in this PR.

## Test Plan 

How did you test the new or updated feature?

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

.changeset/tall-doors-guess.md

@@ -0,0 +1,5 @@
+---
+'@mysten/zklogin': patch
+---
+
+Fix usage of string values in the SDK

sdk/zklogin/src/nonce.ts

@@ -1,34 +1,26 @@
 // Copyright (c) Mysten Labs, Inc.
 // SPDX-License-Identifier: Apache-2.0
 
-import { toB64, toHEX } from '@mysten/bcs';
 import { PublicKey } from '@mysten/sui.js/cryptography';
 import { toBigEndianBytes } from '@mysten/sui.js/zklogin';
 import { randomBytes } from '@noble/hashes/utils';
 import { base64url } from 'jose';
 
 import { poseidonHash } from './poseidon.js';
+import { toBigIntBE } from './utils.js';
 
 const NONCE_LENGTH = 27;
 
-function toBigIntBE(bytes: Uint8Array) {
-	const hex = toHEX(bytes);
-	if (hex.length === 0) {
-		return BigInt(0);
-	}
-	return BigInt(`0x${hex}`);
-}
-
 export function generateRandomness() {
 	// Once Node 20 enters LTS, we can just use crypto.getRandomValues(new Uint8Array(16)), but until then this improves compatibility:
-	return toB64(randomBytes(16));
+	return String(toBigIntBE(randomBytes(16)));
 }
 
 export function generateNonce(publicKey: PublicKey, maxEpoch: number, randomness: bigint | string) {
 	const publicKeyBytes = toBigIntBE(publicKey.toSuiBytes());
 	const eph_public_key_0 = publicKeyBytes / 2n ** 128n;
 	const eph_public_key_1 = publicKeyBytes % 2n ** 128n;
-	const bigNum = poseidonHash([eph_public_key_0, eph_public_key_1, maxEpoch, randomness]);
+	const bigNum = poseidonHash([eph_public_key_0, eph_public_key_1, maxEpoch, BigInt(randomness)]);
 	const Z = toBigEndianBytes(bigNum, 20);
 	const nonce = base64url.encode(Z);
 	if (nonce.length !== NONCE_LENGTH) {

sdk/zklogin/src/utils.ts

@@ -1,7 +1,7 @@
 // Copyright (c) Mysten Labs, Inc.
 // SPDX-License-Identifier: Apache-2.0
 
-import { toB64 } from '@mysten/bcs';
+import { toHEX } from '@mysten/bcs';
 import { PublicKey } from '@mysten/sui.js/cryptography';
 
 import { poseidonHash } from './poseidon.js';
@@ -12,7 +12,15 @@ export const MAX_AUD_VALUE_LENGTH = 145;
 const PACK_WIDTH = 248;
 
 export function getExtendedEphemeralPublicKey(publicKey: PublicKey) {
-	return toB64(publicKey.toSuiBytes());
+	return String(toBigIntBE(publicKey.toSuiBytes()));
+}
+
+export function toBigIntBE(bytes: Uint8Array) {
+	const hex = toHEX(bytes);
+	if (hex.length === 0) {
+		return BigInt(0);
+	}
+	return BigInt(`0x${hex}`);
 }
 
 /**
@@ -71,6 +79,6 @@ export function genAddressSeed(
 		hashASCIIStrToField(name, max_name_length),
 		hashASCIIStrToField(value, max_value_length),
 		hashASCIIStrToField(aud, max_aud_length),
-		poseidonHash([salt]),
+		poseidonHash([BigInt(salt)]),
 	]);
 }

sdk/zklogin/test/nonce.test.ts

@@ -0,0 +1,19 @@
+// Copyright (c) Mysten Labs, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+import { expect, test } from 'vitest';
+
+import { Ed25519Keypair } from '../../typescript/src/keypairs/ed25519';
+import { generateNonce, generateRandomness } from '../src';
+
+test('can generate using `generateRandomness`', () => {
+	const kp = Ed25519Keypair.fromSecretKey(new Uint8Array(32));
+	const randomness = generateRandomness();
+	expect(generateNonce(kp.getPublicKey(), 0, randomness)).toBeTypeOf('string');
+});
+
+test('can generate using a bigint', () => {
+	const kp = Ed25519Keypair.fromSecretKey(new Uint8Array(32));
+	const randomness = 0n;
+	expect(generateNonce(kp.getPublicKey(), 0, randomness)).toBeTypeOf('string');
+});