SMB Validation

Can a single restricted login suffice as an electronic signature?

No. The operator has to indicate intent when signing something, and he has to re-enter the user ID/password (shows awareness that he is executing a signature) and give the meaning for the e-sig. To support this, Part 11 §11.50, states that signed e-records shall contain information associated with the signing that indicates the printed name of the signer, the date/time, and the meaning, and that these items shall be included in any human readable form of the record.