public static void addAuthHeader(WebRequest request, string resource, string awsAccessKeyId, string awsSecretAccessKey)
{
if (request.Headers[ALTERNATIVE_DATE_HEADER] == null)
{
request.Headers.Add(ALTERNATIVE_DATE_HEADER, getHttpDate());
}
string canonicalString = makeCanonicalString(resource, request);
string encodedCanonical = encode(awsSecretAccessKey, canonicalString, false);
request.Headers.Add("Authorization", "AWS " + awsAccessKeyId + ":" + encodedCanonical);
}