md5_and_modulo.sql

WITH input AS (SELECT MD5('some input string') AS input, 20 AS modulo),
mods AS (
SELECT
STRTOL(SUBSTRING(input,1,8),16) % modulo AS a,
STRTOL(SUBSTRING(input,9,8), 16) % modulo AS b,
STRTOL(SUBSTRING(input,17,8), 16) % modulo AS c,
STRTOL(SUBSTRING(input,25,8), 16) % modulo AS d,
POW(POW(16 % modulo, 4)::INT % modulo, 2)::INT % modulo AS offset_multiplier,
modulo
FROM input)

SELECT ((((a * offset_multiplier) + b) * offset_multiplier + c) * offset_multiplier + d) % modulo AS result
FROM mods