An
audio signal signing module (500) is provided which, comprises a Turing tester (700) configured to perform a
Turing test to differentiate a human from a non-human as user, an input (502) configured to receive a
digital audio signal (121), a block divider (130) configured to divide the received
digital audio signal (121) into a sequence of a plurality of audio blocks (131), an audio feature extractor (150) configured to extract audio features (151) from a current audio block (131), a signature unit (140) configured to generate a signature (144) associated to the current audio block (131) by applying a private key (142) to the audio features (151) and configured to provide signed
authentication information (141), which comprises the extracted audio features (151) and the signature (144), wherein the signed
authentication information (141) is outputted to a memory (600), an information embedder (160) configured to generate an audio block (131) with embedded information (161) by embedding
authentication access information (162) into the current audio block (131), wherein the authentication access information (162) comprises information on how and / or where the signed
authentication information (141) is retrievable from the memory (600), and an audio output (190) configured to output an authenticable
audio signal (501) comprising a sequence of the audio blocks with embedded authentication access information (161), In a first operating mode the Turing tester is configured to output a question or prompt which the user must answer, receive an answer in form of an
audio signal captured via at least one
microphone, analyze the answer captured by the
microphone, compare the received answer to a correct answer of the question or prompt, and activate a second operating mode, when the received answer is correct and user has passed the
Turing test. The second operating mode is activated after completion of the first operating mode to generate an authenticable audio
signal (501) via the input (502), the block divider (130), the audio feature extractor (150), the signature unit (140) and information embedder (160).