We can´t say that a SURNAME is a sephardic or a christian name. Only the lineages are jews, chistians, etc.
With the SURNAME Alfaro there are LINEAGES of conversed jews, prosecuted by the Inquisition in the New World, and other jew lineages that lived in Portugal.
Also with the SURNAME Alfaro there were severals LINEAGES of hidalgos in Spain, who fought during the Reconquest. They had an old christian origin. We can found christians called Alfaro since the XII century.
And we can find people with the SURNAME Alfaro that were peasants. In America, indians called ALFARO, in Philipines natives with this surname. Even people of black race called Alfaro.
...So ALFARO may be a sephardic name, but may have a lot of differents origins also.