Abstract: Based on a generalized chaos synchronization (GCS) system and a generalized Sinai map, a non-symmetric digital cryptographic scheme was proposed. The scheme could hide, in conventional sound signals, various kinds of formatted images which a computer can recognize, realizing information disguise and hiding. This scheme with 24 keys could recover hidden images without any errors. The key space of the scheme was as large as 10³⁶⁰. The scheme had data origin authentication function. Even if a receiver could not communicate with the sender of encrypted data, the receiver can still conftrm whether the data are altered by an intruder. The scheme could be applied in the internet image transmissions disguised via sound signals. The analysis of the key space, the sensitivity of key parameters and the correlation of encrypted signals implied that this scheme had good security.