// Create new Mac instance for thread safety without blocking other operations
            Mac mac;
            try {
                mac = createMacInstance();
            } catch (GeneralSecurityException e) {
                log.error("Failed to create Mac instance for signing", e);
                throw new RuntimeException("Failed to create Mac instance", e);
            }

      Providers.setProviderList(providers);
    }
  }

  public void testMultipleUpdates() throws Exception {
    Mac mac = Mac.getInstance("HmacSHA1");
    mac.init(SHA1_KEY);
    mac.update("hello".getBytes(UTF_8));
    mac.update("world".getBytes(UTF_8));

    assertEquals(
        HashCode.fromBytes(mac.doFinal()),
        Hashing.hmacSha1(SHA1_KEY)
            .newHasher()
            .putString("hello", UTF_8)

        int ms_usage = mapArcfourMD5KeyUsage(keyusage);
        Mac mac = Mac.getInstance("HmacMD5");
        MessageDigest md = MessageDigest.getInstance("MD5");
        mac.init(key);
        byte[] dk = mac.doFinal(MD5_CONSTANT);
        try {
            // little endian
            md.update((byte) (ms_usage & 0xFF));

# ==============================================================================
#
# macOS specific setup for all TF scripts.
#

# Mac version of Core utilities differ in usage. Since our scripts are written
# with the GNU style, we need to set GNU utilities to be default on Mac.
if [[ -n "$(which grealpath)" ]] &&  [[ -n "$(which gstat)" ]]; then
  alias realpath=grealpath
  alias stat=gstat

        System.arraycopy(name.getBytes("US-ASCII"), 0, src, srcIndex + 13, 16);
        src[srcIndex + 28] = 0x00; // hex code
        src[srcIndex + 29] = 0x04; // flags
        // MAC address (6 bytes)
        byte[] mac = new byte[6];
        System.arraycopy(mac, 0, src, srcIndex + 31, 6);
        // Stats (6 bytes)
        byte[] stats = new byte[6];
        System.arraycopy(stats, 0, src, srcIndex + 37, 6);

    /**
     * Retrieves the MAC address of the remote network interface. Samba returns all zeros.
     *
     * @param tc
     *            context to use
     *
     * @return the MAC address as an array of six bytes
     * @throws UnknownHostException
     *             if the host cannot be resolved to
     *             determine the MAC address.
     */

    private int updates;
    private int signSequence;

    /**
     * Constructs a new signing digest with the specified MAC signing key.
     *
     * @param macSigningKey the MAC signing key for message authentication
     * @param bypass whether to bypass MAC signing
     * @throws SmbException if MD5 algorithm is not available
     */

        // Using a key with a known value for reproducibility
        SecretKeySpec key = new SecretKeySpec(new byte[16], "ARCFOUR");
        byte[] mac = PacMac.calculateMacArcfourHMACMD5(3, key, TEST_DATA);
        assertNotNull(mac);
        assertEquals(16, mac.length);

        // Test with a different key usage
        byte[] mac2 = PacMac.calculateMacArcfourHMACMD5(9, key, TEST_DATA);
        assertNotNull(mac2);

```

/// tip

Tham số thứ hai cho <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> là giá trị mặc định để trả về.

Nếu không được cung cấp, nó mặc định là `None`, ở đây chúng ta cung cấp `"World"` là giá trị mặc định để sử dụng.

///

Sau đó bạn có thể gọi chương trình Python:

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console

 * message integrity and authenticity using MAC (Message Authentication Code) algorithms.
 *
 * @author mbechler
 */
public interface SMBSigningDigest {

    /**
     * Performs MAC signing of the SMB. This is done as follows.
     * The signature field of the SMB is overwritten with the sequence number;
     * The MD5 digest of the MAC signing key + the entire SMB is taken;