In our ancient history, there are innumerable codes and ciphers that lay mysterious till date but are in some way or the other important for the researchers and scholars to know more on the subject. Following is a compilation of some of the codes that have been enlisted by learned people across.
Voynich Manuscript –
The Voynich manuscript is an illustrated codex hand-written in an unknown, possibly meaningless writing system. The manuscript is named after Wilfrid Voynich, a Polish book dealer who purchased it in 1912.
At least 400 years old, this is a 232-page illuminated manuscript entirely written in a secret script. It is filled with copious drawings of unidentified plants, herbal recipes of some sort, astrological diagrams, and many small human figures in strange plumbing-like contraptions.
The script is unlike anything else in existence, but is written in a confident style, seemingly by someone who was very comfortable with it. In 2004 there were some compelling arguments which described a technique that would seemingly prove that the manuscript was a hoax, but to date, none of the described techniques have been able to replicate a single section of the Manuscript, so speculations continue.
The Voynich manuscript has been studied by many professional and amateur cryptographers, including American and British codebreakers from both World War I and World War II. The manuscript has never been demonstrably deciphered, and the mystery of its meaning and origin has excited the popular imagination, making it the subject of novels and speculation.
References: https://en.wikipedia.org/wiki/Voynich_manuscript
Dorabella Cipher –
In 1897, the well-known composer Edward Elgar (of “Pomp and Circumstance” fame) sent an encrypted message to a 23-year-old friend. To this day, it still has not been solved.
Zodiac killer ciphers –
From 1966 to 1974, the Zodiac serial Killer sent more than 20 written communications to the police official. Most of these messages have been cracked, but there are still some that remain unsolved. The killer was never caught.
Rongorongo Script of Easter Island –
In 1868, Europeans first reported seeing wooden tablet, on the incredibly remote Easter island in the south; Pacific. The tablets were covered with an unknown hieroglyphic script. Only 20 or so tablets are thought to be in existence, with little progress in determining what it is that they say.
Indus Script –
The Indus Valley civilization flourished around 2600 to 1800 BC on the Indian sub-continent, leaving behind thousands of objects inscribed with a pictographic script that seems to have been composed of about 400 signs. A Great deal of work has been done on analyzing the messages that are available, but to this date the script still has not been deciphered.
There are several other ancient writing systems that are still under wraps, such as the 13,000 Etruscan inscriptions, Proto-Elamite, Meroitic and various other obscure glyphs. The researchers have started their studies and will hopefully crack the few too.
References- Wikipedia, VS Publishers