A simple evolutionarily stable strategy (ESS) model of identity advertisement is presented, which is applicable to many different situations, ranging from parental recognition of young to recognition of kin by workers in social insect colonies that comprise several genetically distinct lineages. The model assumes that the receiver may respond favourably or unfavourably to the signaller, but that it cannot immediately determine which type of response is appropriate. The signaller, who always benefits by eliciting a favourable response (but is unaware of which type of response is appropriate for the receiver), may choose to reveal or conceal its identity, making the task of discrimination easier or harder for the receiver. The evolutionarily stable outcome of the model depends on the probability that an unfavourable response is appropriate, the relative costs to the receiver of acceptance and rejection errors, and the relative benefits to the signaller of eliciting a favourable response when this is appropriate and when it is inappropriate for the receiver. High costs of acceptance errors to the receiver, and high benefits of appropriate favourable responses to the signaller, favour provision of distinctive identity cues: so, paradoxically, does a high probability that an unfavourable response is appropriate. However, under a wide range of conditions, selection favours the withholding of signature cues, which prevents discrimination by the receiver. Finally, if the signaller must provide some information to elicit a favourable response, but stands to gain more from such a response when it is undesirable, it may do best to provide partial but incomplete information about its identity.