In this paper a new approach for combining biometric authentication and digital watermarking is presented. A digital audio watermark method is used to embed metadata into the reference data of biometric speaker recognition. Metadata in our context may consist of feature template representations complementary to the speech modality, such as iris codes or biometric hashes, ancillary information about the social, cultural or biological context of the originator of the biometric data or technical details of the sensor. We suggest a well-known watermark embedding technique based on LSB (least significant bit) modulation for this purpose, perform experiments based on a database taken from 33 subjects and 5 different utterances and a known cepstrum based speaker recognition algorithm in verification mode. The goal is to perform a first evaluation of the recognition precision for our selected algorithm. The first tests show that the recognition precision is not significantly deteriorated by the embedding of the information, as in three out of five cases, no degradation was observed at all and in the worst case the relative increase in false recognition was limited to 1%.