The NSRL collects software from various sources and computes message digests, or cryptographic hash values, from them. The digests are stored in the Reference Data Set (RDS) which can be used to identify "known" files on digital media. This will help alleviate much of the effort involved in determining which files are important as evidence on computers or file systems that have been seized as part of criminal investigations.[3] Although the RDS hashset contains some malicious software (such as steganography and hacking tools) it does not contain illicit material (e.g. indecent images).