403 forbidden error - Accessing Amazon S3 bucket using Http GET Request in c#

I am writing an c# code that is trying to access the Amazon S3 bucket through REST calls. The code makes a get request to an xml file created in the s3 bucket.

I am using the secret key and access Id to create a signature that will be used in the authorization header.

The Signature I created is based on Amazon's documentation, http://ift.tt/1hobFjy

I have provided permissions for authenticated requests to access the xml file in the s3 bucket.

The Code I am using,

string AccessId = "xyz";
string SecretKey = "xyz";
string bucketName = "bucket";
string filename = "filename.xml";
string httpDate = DateTime.UtcNow.ToString("ddd, dd MMM yyyy HH:mm:ss +0000\n");
string StringtoSign = "GET\n"
                      + "\n"
                      + "\n"
                      + httpDate + "\n"  
                      + "/bucketName/filename.xml";

//Creating Signature
     Encoding e_UTF
     Encoding e_ASCI = new ASCIIEncoding();
     byte[] key_new= e_ASCI.GetBytes(SecretKey);
     byte[] message_new = e_UTF.GetBytes(StringtoSign);
     HMACSHA1 myhmacsha1 = new HMACSHA1(key_new);
     byte[] final=myhmacsha1.ComputeHash(message_new);
     string AWSSignature = Convert.ToBase64String(final);

// Sending request
HttpWebRequest request =    (HttpWebRequest)HttpWebRequest.Create("http://"+bucketname+".s3-us-west-2.amazonaws.com/"+filename);
request.Method = "GET";
request.Headers.Add("Authorization", "AWS"+ " " + AccessId + ":" + AWSSignature);
try
{
    // Getting response
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    Stream stream = response.GetResponseStream();
    StreamReader sr = new StreamReader(stream);
    String ResStr = sr.ReadToEnd();
    Console.WriteLine(ResStr);
}
catch (WebException ex)
{
    var Resp = (HttpWebResponse)ex.Response;
    Stream new_str=Resp.GetResponseStream();
    StreamReader stred = new StreamReader(new_str);
    MessageBox.Show(stred.ReadToEnd().ToString());
}

The Same Code works fine if I set the permissions for the xml file as public. So it has got to do something with the signature. I am not sure what am doing wrong. It would be great if someone can have a look at it.