java - Android:Java:使用 key 而不是密码解密 AES

Question

我正在使用代码 fragment 来解密 AES 文件。

但是，我想使用 key 文件而不是密码来解密文件。

我需要在下面的代码中进行哪些更改才能实现这一点？

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class AESCrypto {

    public static String encrypt(String seed, String cleartext) throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] result = encrypt(rawKey, cleartext.getBytes());
        return Converters.toHex(result);
    }

    public static String decrypt(String seed, String encrypted) throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] enc = Converters.toByte(encrypted);
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

    public static byte[] getRawKey(byte[] seed) throws Exception {
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
        sr.setSeed(seed);
        try {
            kgen.init(256, sr);
            } catch (Exception e) {
            // Log.w(LOG, "This device doesn't support 256 bits, trying 192 bits.");
            try {
            kgen.init(192, sr);
            } catch (Exception e1) {
            // Log.w(LOG, "This device doesn't support 192 bits, trying 128 bits.");
            kgen.init(128, sr);
            }
        }
        SecretKey skey = kgen.generateKey();
        byte[] raw = skey.getEncoded();
        return raw;
    }

    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
            Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(clear);
            return encrypted;
    }

    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
            Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
            return decrypted;
    }
}

Answer 1

AES key 只不过是随机生成的 16、24 或 32 字节数据。因此，要创建 key 文件，请在其中保存一定数量的随机数据，并使用它来实例化 SecretKeySpec(byte[] data, "AES")。

请注意，为方便起见，SecretKeySpec 也是一个 SecretKey。