HMAC hasher = new HMACSHA256(Encoding.UTF8.GetBytes("secret")); //key
byte[] data = hasher.ComputeHash(Encoding.UTF8.GetBytes("2012-10-01T17:48:56")); //timestamp
Convert.ToBase64String(data); //computed token

$hmac = hash_hmac("sha256", "2012-10-01T17:48:56", "secret");
$hmac = base64_encode($hmac);

$hmac = hash_hmac("sha256", "2012-10-01T17:48:56", "secret", true);
$hmac = base64_encode($hmac);

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