Sure but I think given md5's better performance, and the consequence of a collision being of little impact, I think md5 would be better...

> On 6 Jan 2014, at 11:30 am, Josh Suereth <notifications@github.com> wrote:
> 
> In src/main/scala/com/typesafe/web/sbt/incremental/OpCache.scala:
> 
> > + * Useful methods for working with an OpCache.
> > + */
> > +private[incremental] object OpCache {
> > +
> > +  /**
> > +   * A record stored in a cache. At the moment a record stores
> > +   * a list of files accessed, but the record could be extended to store other
> > +   * information in the future.
> > +   */
> > +  final case class Record(fileHashes: Set[FileHash])
> > +
> > +  /**
> > +   * A hash of a file's content.
> > +   * @param sha1IfExists `Some(sha1)` if the file exists, `None` otherwise.
> > +   */
> > +  final case class FileHash(file: File, sha1IfExists: Option[Bytes])
> It's more about likelihood of collision. You don't want false positives. Odds are poor for both.
> 
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