AWS SignatureDoesNotMatch: The request signature we calculated does not match the signature you provided

I am getting this response to GET request to amazon product api.

    <?xml version="1.0"?>
<ItemSearchErrorResponse xmlns="http://ift.tt/1zDT4Ys"><Error><Code>SignatureDoesNotMatch</Code><Message>The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.</Message></Error><RequestId>9aff7feb-7f9b-4efb-aece-b595b1b7b0e5</RequestId></ItemSearchErrorResponse>

In my javascript, I am generating signature as:

  var string='GET\nwebservices.amazon.in\n/onca/xml\n';
  console.log(string+$.param(paramO));
  var hash = CryptoJS.HmacSHA256(string+$.param(paramO), SecretAccessKey);
  var signature = CryptoJS.enc.Base64.stringify(hash);
  var paramO = {
    Service:'AWSECommerceService',
    Operation:'ItemSearch',
    AWSAccessKeyId:AccessKeyId,
    AssociateTag:AssociateTag,
    Version:'2011-08-01',
    SearchIndex:'All',
    Keywords:name,
    ResponseGroup:'ItemAttributes,OfferSummary',
    Timestamp:timestamp,
    Signature:signature
  };