Building Deterministic Arweave Wallets: Why We Outperformed Existing Libraries

TL;DR:

• The Problem: Existing Arweave libraries failed to generate deterministic wallets (same phrase = different keys), which is catastrophic for wallet restoration.
• The Solution: We built a custom implementation using node-forge to explicitly control the PRNG, ensuring 100% determinism.
• Performance: optimized 2048-bit RSA keys to generate in ~2-3s (vs 60s+) without compromising security.
• Outcome: A rigorously verified, open-source solution that guarantees reliable self-custody, now live in Zelf Wallet.

The Problem with Existing Libraries

// What we expected
const wallet1 = await getKeyFromMnemonic(mnemonic);
const wallet2 = await getKeyFromMnemonic(mnemonic);
console.log(wallet1.address === wallet2.address); // Should be true

// What we got
// false 😱

Building Our Own Solution

1. Explicit PRNG Control

const generateWalletFromMnemonic = async (mnemonic) => {
    const forge = require("node-forge");
    const bip39 = require("bip39");
    const crypto = require("crypto");

    // 1. Derive seed from mnemonic
    const seed = await bip39.mnemonicToSeed(mnemonic);

    // 2. Create deterministic PRNG using SHA-256 hash chain
    let state = seed;
    const customPrng = {
        getBytesSync: (size) => {
            let res = "";
            while (res.length < size) {
                const hasher = crypto.createHash("sha256");
                hasher.update(state);
                state = hasher.digest();
                res += state.toString("binary");
            }
            return res.substring(0, size);
        },
    };

    // 3. Generate RSA key with our PRNG
    const keyPair = forge.pki.rsa.generateKeyPair({
        bits: 2048,
        prng: customPrng,
        workers: -1, // Force main thread
    });

    // 4. Convert to Arweave JWK format
    // ... (conversion logic)
};

2. Performance Optimization

• Are still fully compliant with Arweave's protocol
• Generate in ~2-3 seconds (20x faster)
• Maintain cryptographic security for wallet use cases
• Preserve perfect determinism

3. Rigorous Verification

// Validate key is functional
const data = new TextEncoder().encode("Hello Arweave");
const signature = await arweave.crypto.sign(jwk, data);
const isValid = await arweave.crypto.verify(jwk.n, data, signature);

expect(isValid).toBe(true); // ✅ PASS

The Results

Why This Matters for Web3

The Broader Lesson

1. Test rigorously (we ran determinism tests hundreds of times)
2. Understand the cryptography (not just copy-paste code)
3. Be willing to build from scratch when existing solutions fail

Try It Yourself

1. Download Zelf at zelf.world
2. Import any 12-word mnemonic (or create a new one)
3. Get your Arweave address instantly—and know it'll be the same every time