### Question:
Wallet { public static ECKeyPair decrypt(String password, WalletFile walletFile) throws CipherException { validate(walletFile); WalletFile.Crypto crypto = walletFile.getCrypto(); byte[] mac = Numeric.hexStringToByteArray(crypto.getMac()); byte[] iv = Numeric.hexStringToByteArray(crypto.getCipherparams().getIv()); byte[] cipherText = Numeric.hexStringToByteArray(crypto.getCiphertext()); byte[] derivedKey; WalletFile.KdfParams kdfParams = crypto.getKdfparams(); if (kdfParams instanceof WalletFile.ScryptKdfParams) { WalletFile.ScryptKdfParams scryptKdfParams = (WalletFile.ScryptKdfParams) crypto.getKdfparams(); int dklen = scryptKdfParams.getDklen(); int n = scryptKdfParams.getN(); int p = scryptKdfParams.getP(); int r = scryptKdfParams.getR(); byte[] salt = Numeric.hexStringToByteArray(scryptKdfParams.getSalt()); derivedKey = generateDerivedScryptKey(password.getBytes(UTF_8), salt, n, r, p, dklen); } else if (kdfParams instanceof WalletFile.Aes128CtrKdfParams) { WalletFile.Aes128CtrKdfParams aes128CtrKdfParams = (WalletFile.Aes128CtrKdfParams) crypto.getKdfparams(); int c = aes128CtrKdfParams.getC(); String prf = aes128CtrKdfParams.getPrf(); byte[] salt = Numeric.hexStringToByteArray(aes128CtrKdfParams.getSalt()); derivedKey = generateAes128CtrDerivedKey(password.getBytes(UTF_8), salt, c, prf); } else { throw new CipherException("Unable to deserialize params: " + crypto.getKdf()); } byte[] derivedMac = generateMac(derivedKey, cipherText); if (!Arrays.equals(derivedMac, mac)) { throw new CipherException("Invalid password provided"); } byte[] encryptKey = Arrays.copyOfRange(derivedKey, 0, 16); byte[] privateKey = performCipherOperation(Cipher.DECRYPT_MODE, iv, encryptKey, cipherText); return ECKeyPair.create(privateKey); }  static WalletFile create(String password, ECKeyPair ecKeyPair, int n, int p); static WalletFile createStandard(String password, ECKeyPair ecKeyPair); static WalletFile createLight(String password, ECKeyPair ecKeyPair); static ECKeyPair decrypt(String password, WalletFile walletFile);  }### Answer:
@Test public void testDecryptAes128Ctr() throws Exception { WalletFile walletFile = load(AES_128_CTR); ECKeyPair ecKeyPair = Wallet.decrypt(PASSWORD, walletFile); assertThat(Numeric.toHexStringNoPrefix(ecKeyPair.getPrivateKey()), is(SECRET)); }
@Test public void testDecryptScrypt() throws Exception { WalletFile walletFile = load(SCRYPT); ECKeyPair ecKeyPair = Wallet.decrypt(PASSWORD, walletFile); assertThat(Numeric.toHexStringNoPrefix(ecKeyPair.getPrivateKey()), is(SECRET)); }
@Test public void testDecryptAes128Ctr() throws Exception { WalletFile walletFile = load(AES_128_CTR); ECKeyPair ecKeyPair = Wallet.decrypt(PASSWORD, walletFile); assertEquals(Numeric.toHexStringNoPrefix(ecKeyPair.getPrivateKey()), (SECRET)); }
@Test public void testDecryptScrypt() throws Exception { WalletFile walletFile = load(SCRYPT); ECKeyPair ecKeyPair = Wallet.decrypt(PASSWORD, walletFile); assertEquals(Numeric.toHexStringNoPrefix(ecKeyPair.getPrivateKey()), (SECRET)); }