US Federal Standards (NIST): http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
"For XOFs, the length of the output can be chosen to meet the requirements of individual applications. The XOFs can be specialized to hash functions, subject to additional security considerations, or used in a variety of other applications. The approved uses of XOFs will be specified in NIST Special Publications."
(Check with NSA guy regarding homomorphic tiny crypto)