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# Data APIs MAC Generation

### Confirmation of Funds API MAC Generation

##### MAC Generation Steps

Follow these steps to generate the MAC:

1. The HMAC SHA256 algorithm must be used.
2. The base string should be constructed using the following parameters in the listed order with each followed by a newline "`\n`" character (%x0A):

* `ts` (timestamp in Unix Epoch format)
* `nonce`
* `httpMethod`
* `resourcePath` (URL Encoded(UTF\_8\_ENC))
* `host`
* `port`
* `\n` (one extra character (%x0A))

3. Use `mac_key` as the key (available from the response of the OAuth Get Access Token call).
4. Base-64 encode the output of the raw data.

##### Sample Code to Generate the Confirmation of Funds APIs MAC

```

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.net.URLEncoder;
import java.util.*;

public class DataAuthenticationHeaderGenerator{
	private static final String HMAC_SHA256_ALGORITHM = "HmacSHA256";
	private static final String NONCE_SUFFIX = ":AMEX";
	private static final String UTF_8_ENC = "UTF-8";
	public static void main(String[] args) throws Exception{
 String accessToken = "1e74169f-c7fe-4a68-b486-d3a00c933cff";
 String macKey = "47d06261-e088-4829-bbcd-a07c6d9f22df";
 String httpMethod = "POST";
 String host = "openamex-qa.americanexpress.com";
 String port = "443";
 String resourcePath = "/servicing/v1/card_member/funds/confirmations";
 String authorizationMacToken = generateAuthorizationMacToken(accessToken, macKey, httpMethod, host, port, resourcePath);
 System.out.println(authorizationMacToken);
 }
 public static String generateAuthorizationMacToken(String accessToken, String macKey, String httpMethod, String host, String port, String resourcePath) throws Exception{
 String nonce = UUID.randomUUID().toString() + NONCE_SUFFIX;
 String timeInMillis = String.valueOf((System.currentTimeMillis()));
 StringBuilder baseStringBuilder = new StringBuilder();
 baseStringBuilder.append(timeInMillis);
 baseStringBuilder.append("\n");
 baseStringBuilder.append(nonce);
 baseStringBuilder.append("\n");
 baseStringBuilder.append(httpMethod);
 baseStringBuilder.append("\n");
 baseStringBuilder.append(URLEncoder.encode(resourcePath, UTF_8_ENC));
 baseStringBuilder.append("\n");
 baseStringBuilder.append(host);
 baseStringBuilder.append("\n");
 baseStringBuilder.append(port);
 baseStringBuilder.append("\n");
 baseStringBuilder.append("\n");
 String baseString = baseStringBuilder.toString();
 Mac mac = Mac.getInstance(HMAC_SHA256_ALGORITHM);
 mac.init(new SecretKeySpec(macKey.getBytes(UTF_8_ENC), HMAC_SHA256_ALGORITHM));
 String signatureStr = Base64.getEncoder().encodeToString(mac.doFinal(baseString.getBytes(UTF_8_ENC)));
 StringBuilder macTokenBuilder = new StringBuilder();
 macTokenBuilder.append("MAC id=\"");
 macTokenBuilder.append(accessToken);
 macTokenBuilder.append("\",ts=\"");
 macTokenBuilder.append(timeInMillis);
 macTokenBuilder.append("\",nonce=\"");
 macTokenBuilder.append(nonce);
 macTokenBuilder.append("\",mac=\"");
 macTokenBuilder.append(signatureStr);
 macTokenBuilder.append("\"");
 return macTokenBuilder.toString();
 }
}
```