The Raiders have signed Curtis Riley, according to a tweet from the safety himself. Riley, formerly of the Giants, also visited the Packers and Bengals before joining up with Oakland. 
Riley started in all 16 of the Giants’ games last year and reeled in four interceptions. It was a rough year for the Giants on the whole, but Riley had a strong individual showing.
Riley started his career with the Titans, but he truly put himself on the map last year with the aforementioned picks, plus 75 tackles and five passes defended. However, for what it’s worth, Pro Football Focus only ranked him 79th among 93 eligible safeties.