Android:使用带有iv和密钥的AES 256位加密来加密字符串

Question

SecureRandom random = new SecureRandom(); // quite heavy, look into a lighter method.

String stringToEncrypt = "mypassword";
byte[] realiv = new byte[16];
random.nextBytes(realiv);
Cipher ecipher = Cipher.getInstance("AES");

SecureRandom random = new SecureRandom(); // quite heavy, look into a lighter method.

byte[] realiv = new byte[16];
random.nextBytes(realiv);       

byte[] secret = "somelongsecretkey".getBytes();
SecretKeySpec secretKey = new SecretKeySpec(secret, "AES");
ecipher.init(Cipher.ENCRYPT_MODE, secretKey, random);
byte[] encryptedData = ecipher.doFinal();

但init()唯一需要3个参数.我需要一种方法来做类似的事情:

ecipher.init(Cipher.ENCRYPT_MODE, stringToEncrypt, secretKey, random);

Answer 1

通常,您不需要为具有确定性行为的算法生成随机数的东西.此外,当您使用ECB块模式时,您不需要IV,这是Java默认的模式.确切地说,Java默认"AES/ECB/PKCS5Padding"为in Cipher.getInstance("AES").

所以你应该可以使用这样的代码:

// lets use the actual key value instead of the platform specific character decoding
byte[] secret = Hex.decodeHex("25d6c7fe35b9979a161f2136cd13b0ff".toCharArray());

// that's fine
SecretKeySpec secretKey = new SecretKeySpec(secret, "AES");

// SecureRandom should either be slow or be implemented in hardware
SecureRandom random = new SecureRandom();

// first create the cipher
Cipher eCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

// filled with 00h characters first, use Cipher instance so you can switch algorithms
byte[] realIV = new byte[eCipher.getBlockSize()];

// actually fill with random
random.nextBytes(realIV);

// MISSING: create IvParameterSpec
IvParameterSpec ivSpec = new IvParameterSpec(realIV);

// create the cipher using the IV
eCipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);

// NOTE: you should really not encrypt passwords for verification
String stringToEncrypt = "mypassword";

// convert to bytes first, but don't use the platform encoding
byte[] dataToEncrypt = stringToEncrypt.getBytes(Charset.forName("UTF-8"));

// actually do the encryption using the data
byte[] encryptedData = eCipher.doFinal(dataToEncrypt);

现在看起来好多了.我已经使用Apache commons编解码器来解码十六进制字符串.

请注意,您需要保存realIV与encryptedData和你有没有包括完整性保护,如MAC(口令,你可能不需要,虽然).