--
-- crypt() and gen_salt(): md5
--
SELECT crypt('', '$1$Szzz0yzz');
               crypt                
------------------------------------
 $1$Szzz0yzz$To38XrR3BsbXQW2ZpfKjF1
(1 row)

SELECT crypt('foox', '$1$Szzz0yzz');
               crypt                
------------------------------------
 $1$Szzz0yzz$IYL49cd3t9bllsA7Jmz1M1
(1 row)

CREATE TABLE ctest (data text, res text, salt text);
INSERT INTO ctest VALUES ('password', '', '');
UPDATE ctest SET salt = gen_salt('md5');
UPDATE ctest SET res = crypt(data, salt);
SELECT res = crypt(data, res) AS "worked"
FROM ctest;
 worked 
--------
 t
(1 row)

DROP TABLE ctest;