Private Key

Keystore to private key by web3j

• keystore

  {
      "address":"5b7ca0361e23e18a8f91fd1c5890d50adc8a53c5",
      "crypto":{
          "cipher":"aes-128-ctr",
          "ciphertext":"88655666a1eb7476fae05b2f58f84974f0316e9861a10e93f88763d480a3489f",
          "cipherparams":{
              "iv":"bd0236c1c69de7800c2e17899de439e8"
          },
          "kdf":"scrypt",
          "kdfparams":{
              "dklen":32,
              "n":8192,
              "p":1,
              "r":8,
              "salt":"e1a68d9bbb4991b1b067b049277cc279666d5b66b5b0f87dbe7fd62c9e2654f6"
          },
          "mac":"e380dbb051072576140cbf1a97fd14d616cf8b012f0c7228ecfa966629664592"
      },
      "id":"ab17bbfa-5084-4455-91cc-0ba2644810dd",
      "version":3
  }
  

• test

  import static org.assertj.core.api.Assertions.assertThat;
  
  import com.google.gson.Gson;
  import com.isuncloud.tidewallet.eth.InputData;
  import org.junit.Test;
  import org.web3j.crypto.Wallet;
  import org.web3j.crypto.WalletFile;
  
  public class Test {
  
    @Test
    public void fromKeystore() throws Exception {
      // arrange
      final WalletFile keystore = new WalletFile();
      keystore.setVersion(3);
      keystore.setId("ab17bbfa-5084-4455-91cc-0ba2644810dd");
      keystore.setAddress("5b7ca0361e23e18a8f91fd1c5890d50adc8a53c5");
      final WalletFile.Crypto crypto = new WalletFile.Crypto();
      crypto.setCiphertext("88655666a1eb7476fae05b2f58f84974f0316e9861a10e93f88763d480a3489f");
      final WalletFile.CipherParams cipherparams = new WalletFile.CipherParams();
      cipherparams.setIv("bd0236c1c69de7800c2e17899de439e8");
      crypto.setCipherparams(cipherparams);
      crypto.setCipher("aes-128-ctr");
      crypto.setKdf("scrypt");
  
      final WalletFile.ScryptKdfParams kdfparams = new WalletFile.ScryptKdfParams();
      kdfparams.setDklen(32);
      kdfparams.setSalt("e1a68d9bbb4991b1b067b049277cc279666d5b66b5b0f87dbe7fd62c9e2654f6");
      kdfparams.setN(8192);
      kdfparams.setR(8);
      kdfparams.setP(1);
      crypto.setKdfparams(kdfparams);
      crypto.setMac("e380dbb051072576140cbf1a97fd14d616cf8b012f0c7228ecfa966629664592");
      keystore.setCrypto(crypto);
  
      final String json = new Gson().toJson(keystore);
      final String privateKey = "290867651b60ccef677063030f06ad35037904124099b04deacb15de3bf12cca";
      final String password = "a123kkbox";
  
      // act
      final String result = Wallet.decrypt(password, keystore)
          .getPrivateKey()
          .toString(16);
  
      // assert
      assertThat(result)
          .isNotNull()
          .isEqualTo(privateKey);
    }
  }
  

https://github.com/ethereum/go-ethereum/issues/15407

https://github.com/matthiaszimmermann/ethereum-paper-wallet/blob/master/src/main/java/org/matthiaszimmermann/ethereum/pwg/PaperWallet.java

KeystoreFormat#fromKeystore() of ethereum-harmony is also the solution. It and web3j both use same crypto library - Spongy Castle.

https://github.com/ether-camp/ethereum-harmony/blob/develop/src/main/java/com/ethercamp/harmony/keystore/KeystoreFormat.java

Issue: Cost too long/OOM when n is huge

{
    "address":"0a3114dd29fc5ee0e9cc78109be1a425c2f34f47",
    "crypto":{
        "cipher":"aes-128-ctr",
        "ciphertext":"1cfad4b0d8d4b3ddee9ceb9bd02416a7aa029385839a86e79544243bf4c1468c",
        "cipherparams":{
            "iv":"3dfcf5dd030cb327034ba59c5e283af5"
        },
        "mac":"eadaafb8d49ee673b5ec18b1136eaca997c534115afc6bf9352b1b2a251c9d0d",
        "kdf":"scrypt",
        "kdfparams":{
            "dklen":32,
            "n":262144,
            "r":1,
            "p":8,
            "salt":"c5aec453aaec3ff3846ad9d9b2e307ee211a9989e5a1064ebcbbffa4401a8c7f"
        }
    },
    "id":"8e901909-6bd2-4a56-b09f-866dbcf7bfc6",
    "version":3
}

Using lambdaworks to instead of Spongy Castle crypto library.

https://lhalcyon.com/blockchain-eth-unlock-android/