Generate Ethereum addresses in HD Wallet using public key only bitcoinj web3j

Question

I try to generate Ethereum addresses for the HD Wallet keys implemented with the bitcoinj library, but I got confused:

DeterministicSeed seed = new DeterministicSeed("some seed code here", null, "", 1409478661L); DeterministicKeyChain chain = DeterministicKeyChain.builder().seed(seed).build(); DeterministicKey addrKey = chain.getKeyByPath(HDUtils.parsePath("M/44H/60H/0H/0/0"), true); System.out.println("address from pub=" + Keys.getAddress(Sign.publicKeyFromPrivate(addrKey.getPrivKey())));

this code prints a correct Ethereum address accordingly to https://iancoleman.io/bip39/. Everything is fine here.

But when I try to avoid private key usage and generate non-hardened keys using public keys only I get different results, i.e. the call returns another result:

System.out.println("address from pub=" + Keys.getAddress(addrKey.getPublicKeyAsHex()));

And it looks like the issue is in the "different public keys", i.e. result of the Sign.publicKeyFromPrivate(addrKey.getPrivKey()) and addrKey.getPublicKeyAsHex() are different. I'm not experienced with cryptography, thus it may be a silly question... but I would appreciate any advice here.

Answer 1

Like Bitcoin, Ethereum uses secp256k1. Ethereum addresses are derived as follows:

• Step 1: The 32 bytes x and y coordinate of the public key are concatenated to 64 bytes (where both the x and y coordinate are padded with leading 0x00 values if necessary).

• Step 2: From this the Keccak-256 hash is generated.

• Step 3: The last 20 bytes are used as the Ethereum address.

For the examples used here, the key is generated with:

String mnemonic = "elevator dinosaur switch you armor vote black syrup fork onion nurse illegal trim rocket combine"; DeterministicSeed seed = new DeterministicSeed(mnemonic, null, "", 1409478661L); DeterministicKeyChain chain = DeterministicKeyChain.builder().seed(seed).build(); DeterministicKey addrKey = chain.getKeyByPath(HDUtils.parsePath("M/44H/60H/0H/0/0"), true);

This corresponds to the following public key and Ethereum address:

X: a35bf0fdf5df296cc3600422c3c8af480edb766ff6231521a517eb822dff52cd Y: 5440f87f5689c2929542e75e739ff30cd1e8cb0ef0beb77380d02cd7904978ca Address: 23ad59cc6afff2e508772f69d22b19ffebf579e7

As can also be verified with the website https://iancoleman.io/bip39/.

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