Page History

...

RequestTimestamp
UUID
SessionID
FirmID

Step 2 - Create Signature Using the Secret Key and Canonical FIX Message

The signature is a hash (digest) of the canonical message created in Step 1 using the Secret Key provided by CME.

The Secret Key downloaded from Request Center is Base64 URL Encoded. Customers must decode the secret key first.

...

Example of Creating Signature Using HMAC SHA256 in Java 8+

The HMAC signature is populated in a fixed length string field (i.e. String32Req) since SHA-256 signature is always 32 bytes.

Info
While real logic provides two options to encode this field—as a string and as a byte array—the byte array option should be used.

Encoding options for SHA-256 (256 bits long):

Base64URL encoding FIX ASCII: 6 bits per char = CHAR(44)including padding character
Hex: 4 bits per char = CHAR(64)
- HEX example → 617633EFEF2F98DCA32DD3BD8407122B9B375CF4BC076930F24C1F7A0F930094
Binary: 8 bits per byte = BINARY(32)
- Binary example → byte array:[97, 118, 51, -17, -17, 47, -104, -36, -93, 45, -45, -67, -124, 7, 18, 43, -101, 55, 92, -12, -68, 7, 105, 48, -14, 76, 31, 122, 15, -109, 0, -108]

Info
The signature should be encoded as a byte array.

Signature calculation in Java:

Panel

public byte[] calculateHMAC(final String canonicalRequest, final String userKey) {
    byte[] hash = null;

    try
    {
      // Init HMAC instance
      Mac sha256HMAC;
      sha256HMAC = Mac.getInstance("HmacSHA256");

      // Initialize HMAC instance with the key
      // Decode the key first, since it is base64url encoded

      byte[] decodedUserKey = Base64.getUrlDecoder().decode(userKey);
      SecretKeySpec secretKey = new SecretKeySpec(decodedUserKey, "HmacSHA256");
      sha256HMAC.init(secretKey);

      // Calculate HMAC
      hash = sha256HMAC.doFinal(canonicalRequest.getBytes("UTF-8"));

    } catch (NoSuchAlgorithmException | InvalidKeyException | IllegalStateException | UnsupportedEncodingException e)
    {
      e.printStackTrace();
    }

    return hash;
  }

}

Step 3 - Populate Signature in the Credentials Field

...

Page tree

Versions Compared

Old Version 8

New Version 9

Key

Step 2 - Create Signature Using the Secret Key and Canonical FIX Message

Example of Creating Signature Using HMAC SHA256 in Java 8+