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1public class EncryptionUtility {
2
3    private final static char[] hexArray = "0123456789ABCDEF".toCharArray();
4    private static final String algorithm = "HmacSHA512";
5
6    public static String bytesToHex(byte[] bytes) {
7        char[] hexChars = new char[bytes.length * 2];
8        for (int j = 0; j < bytes.length; j++) {
9            int v = bytes[j] & 0xFF;
10            hexChars[j * 2] = hexArray[v >>> 4];
11            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
12        }
13        return new String(hexChars);
14    }
15
16    public static String calculateHash(String secret, String url) {
17        try {
18            SecretKeySpec secretKey = new SecretKeySpec(secret.getBytes(), algorithm);
19            Mac shaHmac = Mac.getInstance(algorithm);
20            shaHmac.init(secretKey);
21            byte[] hash = shaHmac.doFinal(url.getBytes());
22            return bytesToHex(hash);
23        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
24            e.printStackTrace();
25        }
26        return null;
27    }
28
29    @SuppressLint("SecureRandom")
30    public static String generateNonce() {
31
32        String nonce = null;
33        try {
34            SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
35            if (random != null) {
36                random.setSeed(System.currentTimeMillis());
37            }
38
39            byte[] nonceBytes = new byte[16];
40            if (random != null) {
41                random.nextBytes(nonceBytes);
42            }
43
44            nonce = new String(Base64.encode(nonceBytes, Base64.DEFAULT), "UTF-8");
45
46
47        } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
48
49            e.printStackTrace();
50        }
51
52        return nonce;
53    }
54}