# File lib/aws/core/signature/version_4.rb, line 48 def signature credentials, datetime k_secret = credentials.secret_access_key k_date = hmac("AWS4" + k_secret, datetime[0,8]) k_region = hmac(k_date, region) k_service = hmac(k_region, service) k_credentials = hmac(k_service, 'aws4_request') hexhmac(k_credentials, string_to_sign(datetime)) end