A rate-distortion problem for a communication system with a secondary decoder to be hindered

A rate-distortion problem is considered for a communication system (f, φ₁) with a secondary decoder φ₂ to be hindered which uses a different distortion measure from the primary system. The least achievable distortion of the secondary decoder is evaluated for the most secure primary system. Source coding for sources with additional outputs to be kept secret from the receiver or wiretappers is also discussed. Security is evaluated by distortion measures instead of the equivocation function used by H. Tamamoto (1983)