优化下列代码，使能同时根据计算出的低等级密钥得出更低一级密钥并一同输出：String highKey = request.getParameter("highKey"); MessageDigest digest = MessageDigest.getInstance("SHA-256"); byte[] highKeyHash = digest.digest(highKey.getBytes(StandardCharsets.UTF_8)); byte[] lowKeyHash = digest.digest("lowKey".getBytes(StandardCharsets.UTF_8)); // 计算异或值 byte[] xorValue = new byte[highKeyHash.length]; for (int i = 0; i < highKeyHash.length; i++) { xorValue[i] = (byte) (highKeyHash[i] ^ lowKeyHash[i]); } // 计算低层级密钥 byte[] lowKey = new byte[highKeyHash.length]; for (int i = 0; i < highKeyHash.length; i++) { lowKey[i] = (byte) (highKeyHash[i] ^ xorValue[i]); } // 创建低层级密钥对象 SecretKey secretKey = new SecretKeySpec(lowKey, "AES"); out.println("High Key: " + highKey + "<br>"); out.println("Low Key: " + new String(secretKey.getEncoded(), StandardCharsets.UTF_8));

可以将计算更低一级密钥的部分提取出来，同时计算出高等级密钥、低等级密钥和更低一级密钥，如下所示：

String highKey = request.getParameter("highKey");
byte[] highKeyBytes = highKey.getBytes(StandardCharsets.UTF_8);
byte[] lowKeyBytes = "lowKey".getBytes(StandardCharsets.UTF_8);
byte[] lowerKeyBytes = "lowerKey".getBytes(StandardCharsets.UTF_8);

MessageDigest digest = MessageDigest.getInstance("SHA-256");

byte[] highKeyHash = digest.digest(highKeyBytes);
byte[] lowKeyHash = digest.digest(lowKeyBytes);

// 计算异或值
byte[] xorValue = new byte[highKeyHash.length];
for (int i = 0; i < highKeyHash.length; i++) {
    xorValue[i] = (byte) (highKeyHash[i] ^ lowKeyHash[i]);
}

// 计算低层级密钥
byte[] lowKey = new byte[highKeyHash.length];
for (int i = 0; i < highKeyHash.length; i++) {
    lowKey[i] = (byte) (highKeyHash[i] ^ xorValue[i]);
}

// 计算更低一级密钥
byte[] lowerKey = new byte[highKeyHash.length];
for (int i = 0; i < highKeyHash.length; i++) {
    lowerKey[i] = (byte) (lowKey[i] ^ xorValue[i]);
}

// 创建更低一级密钥对象
SecretKey lowerSecretKey = new SecretKeySpec(lowerKey, "AES");

out.println("High Key: " + highKey + "<br>");
out.println("Low Key: " + new String(lowKey, StandardCharsets.UTF_8) + "<br>");
out.println("Lower Key: " + new String(lowerSecretKey.getEncoded(), StandardCharsets.UTF_8));

这样可以避免重复计算哈希值，提高代码的效率。同时，将更低一级密钥的计算也加入其中，使得代码更加完整。