Need small output? Truncate the output of SHA-256. What "easy to compute" means? Performance? Use BLAKE2. Code complexity? sha256() is only 3 letters more than

Need small output? Truncate the output of SHA-256. What "easy to compute" means? Performance? Use BLAKE2. Code complexity? sha256() is only 3 letters more than md5() (you're probably not writing your own implementation). Asking other people (especially, not professional cryptographers) to try to break your system which knowingly uses insecure primitives is an awful way to evaluate system security.