Android：使用iv和密钥通过AES 256位加密对字符串进行加密

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()只有3个参数。我需要一种方法来做这样的事情：

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对象。此外，在使用ECB块模式时，您不需要IV，这是Java默认设置。确切地说，Java默认为中的"AES/ECB/PKCS5Padding"for
Cipher.getInstance("AES")。

因此，您应该可以使用如下代码：

// 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。我已使用Apache Commons编解码器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）。