An audio fingerprint is a content-based compact signature that summarizes an audio recording. Audio fingerprinting technologies have recently attracted attention since they allow the monitoring of audio independently of its format and without the need of meta-data or watermark embedding. The different approaches to fingerprinting are usually described with different rationales and terminology depending on the background: pattern matching, multimedia (music) information retrieval or cryptography (robust hashing). In this paper, we review different techniques mapping functional parts to blocks of a unified framework.