Election Obligations & Standards Database
"As an additional security measure and safeguard against fraud, a number of countries use voting procedures that require that ballots be placed in envelopes before being placed in the ballot box."
OSCE (ODIHR): Election Observation Handbook (Fifth Edition)
, p. 43
Election Observation Handbook (Fifth Edition)
The system for balloting (paper, electronic, or otherwise) should ensure the secrecy of a voter's choice.