Mifare Ultralight:锁定特定页面 [英] Mifare Ultralight: lock specific pages

问题描述

我从这个链接(Mifare Ultralight C Lock)得到了参考，让所有页面都在只读的 Mifare Ultralight 标签.

I got reference from this link (Mifare Ultralight C Lock) to make all pages on a Mifare Ultralight tag read-only.

我可以在 Android 上成功地在 Mifare Ultralight 标签上写一条消息.现在我想锁定第 4 到 7 页(或任何特定页面).上面的链接只显示了如何锁定所有页面.如何锁定特定页面?

I can write a message on a Mifare Ultralight tag successfully on Android. Now I want to lock pages 4 to 7 (or any specific page). The above link only shows how to lock all pages. How I can lock specific pages?

此代码锁定所有页面:

mifare.transceive(new byte[] {
    (byte)0xA2,  /* CMD = WRITE */
    (byte)0x02,  /* PAGE = 2    */
    (byte)0x00, (byte)0x00, (byte)0xFF, (byte)0xFF  /* DATA = lock pages 3..15*/
});

public static boolean writeOnMifareUltralight(Context _context, Tag tag,String pageData, int i) {
    byte[]result;
    MifareUltralight mifare = null;
    try {

        mifare = MifareUltralight.get(tag);
        mifare.connect();
        mifare.writePage(i, pageData.getBytes(Charset.forName("US-ASCII")));

        mifare.transceive(new byte[] {
            (byte)0xA2,  /* CMD = WRITE */
            (byte)0x02,  /* PAGE = 2    */
            (byte)0x00, (byte)0x00, (byte)0xFF, (byte)0xFF/* DATA = lock pages 3..15*/
        });
    } catch (Exception ex) {
        ex.printStackTrace();
        Log.d("mtw", ex.getMessage());
        // return false;
    } finally {
        try {
            mifare.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
    return true;
}

推荐答案

MIFARE Ultralight 的锁定字节使用一位锁定一个块.此外，它们包含 3 个块锁定位，用于控制锁定字节本身的锁定状态.

The lock bytes of MIFARE Ultralight use one bit to lock one block. In addition they contain 3 block locking bits that control the lock status of the lock bytes themselves.

• 字节 2(第 2 页):第 3-7 位是第 3-7 页的锁定位.因此，第 3 位锁定第 3 页，第 4 位锁定第 4 页，依此类推.低三位是块锁定位.第 0 位锁定第 3 页的锁定位，第 1 位锁定第 4-9 页的锁定位，第 2 位锁定第 10-15 页的锁定位.

• Byte 2 (on page 2): Bits 3-7 are the lock bits for pages 3-7. Thus, bit 3 locks page 3, bit 4 locks page 4, etc. The lower three bits are the block locking bits. Bit 0 locks the lock bit for page 3, bit 1 locks the lock bits for pages 4-9, and bit 2 locks the lock bits for pages 10-15.

字节 3(第 2 页):第 0-7 位是第 8-15 页的锁定位.因此，位 0 锁定第 8 页，位 1 锁定第 9 页，依此类推.

Byte 3 (on page 2): Bits 0-7 are the lock bits for pages 8-15. Thus, bit 0 locks page 8, bit 1 locks page 9, etc.

例如，要锁定第 4-7 页，您可以使用以下命令:

So, for example, to lock pages 4-7, you could use the following command:

mifare.transceive(new byte[] {
    (byte)0xA2,  /* CMD = WRITE */
    (byte)0x02,  /* PAGE = 2    */
    (byte)0x00, (byte)0x00, (byte)0xF0, (byte)0x00 /* DATA = lock pages 4..7*/
});

请注意，您也可以简单地使用 mifare.writePage() 代替 mifare.transceive():

Note that instead of mifare.transceive() you could also simply use mifare.writePage():

mifare.writePage(2, new byte[] {
    (byte)0x00, (byte)0x00, (byte)0xF0, (byte)0x00 /* DATA = lock pages 4..7*/
});

请记住，锁定位是一次性可编程的.因此，一旦锁定位设置为逻辑 1(即 LOCKED)，它就不能反转为逻辑 0(即 UNLOCKED).

Keep in mind that lock bits are one-time-programmable. Hence, once a lock bit is set to logical 1 (i.e. LOCKED), it can't be reversed to a logical 0 (i.e. UNLOCKED).

这也允许您一次设置一个锁定位.例如，要设置页面 i LOCKED (where 3 <= i <= 15 !!!)，这样的事情应该可以工作:

This also allows you to set one lock bit at a time. For instance, to set page i LOCKED (where 3 <= i <= 15 !!!), something like this should work:

mifare.transceive(new byte[] {
    (byte)0xA2,  /* CMD = WRITE */
    (byte)0x02,  /* PAGE = 2    */
    (byte)0x00, (byte)0x00, (byte)((1<<i) & 0x0FF), (byte)(((1<<i)>>>8) & 0x0FF)
});

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