Digital Signature Algorithm for large files - bottle-necked by hash function?
It is potentially a bottleneck, but will it be a problem in practice?  My phone doesn't have 10TB of storage, and if the files are remote the network speed will be the limiting factor.  There are other strategies possible, like computing hashes as the data is transferred to the device, or hash trees for updating a hash without re-computing the whole thing (for e.g. a small edit to a file).