Among all classes of DSC, Class-3 Digital Signature offers the highest security. Applicant has option to buy just the signature only, or along with encryption called as "Combo".
Business firms registered outside India need Class-3 Digital Signature to sign official Government documents such as tender submission or Indian Railways. Paper-less process is convenient with faster turnaround time.
To submit high value tenders on government portals, Class-3 DSC is required with encryption combo. If TIA require encryption, applicant must buy Combo : (1) Signature and (2) Encryption.
If encryption is not required, applicant may choose to buy just the Signature Only.
Vendor / Contractor may use Class-3 DSC for logging into tender portal and submit bids. It can be used for registering patents / trademarks as well.