The PRIMARY reason for using digital signatures is to ensure data:
Digital signatures provide integrity because the digital signature of a signed message (file, mail,
document, etc.) changes every time a single bit of the document changes; thus, a signed document
cannot be altered. Depending on the mechanism chosen to implement a digital signature, the
mechanism might be able to ensure data confidentiality or even timeliness, but this is not assured.
Availability is not related to digital signatures.