The Zodiac cipher is an unsolved series of encrypted messages sent by the Zodiac Killer, an unidentified serial killer active in Northern California during the late 1960s and early 1970s. As a cryptanalysis challenge, the Zodiac cipher remains a topic of ongoing research and fascination in the tech community, with cryptographers and amateur sleuths continuing to study and attempt to decipher the codes, shedding light on the intersection of cryptography, forensic analysis, and true crime investigation.