Mnemonic to EOS PrivateKey

EOSKey.java

class EOSKey {
  // Generate EOS owner pk and active pk from mnemonic
  private static List<byte[]> calcDefaultKeys(List<String> mnemonics, String path) {
    // Step 1. Get chaincode at m/44'/194' 
    // EOS Coin type is defined at SLIP44 ref: https://github.com/satoshilabs/slips/blob/master/slip-0044.md
    // We believe that chaincode are more private
    MnemonicUtil.validateMnemonics(mnemonics);
    DeterministicSeed seed = new DeterministicSeed(mnemonics, null, "", 0L);
    DeterministicKeyChain keyChain = DeterministicKeyChain.builder().seed(seed).build();
    DeterministicKey parent = keyChain.getKeyByPath(BIP44Util.generatePath(path), true);
    byte[] chainCode = parent.getChainCode();
    
    // Step 2. Generate MasterPrivateKey 
    byte[] chainIDBuffer = NumericUtil.hexToBytes(ChainId.EOS_MAINNET);
    byte[] masterPrivateKeyBytes = Hash.hmacSHA256(chainIDBuffer, chainCode);
    
    // Step3. Deriving the subkeys using the MasterPrivateKey
    byte[] ownerKey = Hash.sha256(ByteUtil.concat(masterPrivateKeyBytes, "owner".getBytes(Charset.forName("UTF-8"))));
    byte[] activeKey = Hash.sha256(ByteUtil.concat(ownerKey, "active".getBytes(Charset.forName("UTF-8"))));
    
    // Why is sha256 hasing instead of BIP44? You can check this: https://github.com/EOSIO/eosjs-ecc/issues/7
    // I pasted part of that as follow:
    // For BIP44, EOS is different. It does not have change addresses. Change addresses in BIP44 are fine but for
    // contract permissions that are not a good fit. Due to the elliptic curve math derived keys on the same 
    // hierarchical level have a weaker security profile that make them unsafe. 
    // For example, one private key and a chain code can revile all private keys at that level and lower levels. 
    // So, this is better suited for flat and redundant change addresses but not suited for more meaningful contract permissions.
    // 
    // Deriving keys are done in binary and use only sha256 hashing that does not involve any elliptic curve math.
    // So, while EOS needs something different it is actually easier to implement and understand.
    
    List<byte[]> keys = new ArrayList<>(3);
    keys.add(masterPrivateKeyBytes);
    keys.add(ownerKey);
    keys.add(activeKey);
    return keys;
  }
  
  private void testCase() {
    // Input:
    // mnemonic = inject kidney empty canal shadow pact comfort wife crush horse wife sketch
    // chainID = aca376f206b8fc25a6ed44dbdc66547c36c6c33e3a119ffbeaef943642f0e906
    // Output: (test case checks public key not private key)
    // ownerPublicKey = "EOS7tpXQ1thFJ69ZXDqqEan7GMmuWdcptKmwgbs7n1cnx3hWPw3jw"
    // activePublicKey = "EOS5SxZMjhKiXsmjxac8HBx56wWdZV1sCLZESh3ys1rzbMn4FUumU"
  }
}