Longest time to crack a code
301 Years
United Kingdom ()

The Vigenère Cipher, which uses a polyalphabetic system of encryption, was so effective that it took over 300 years before a method could be found to crack it. The Cipher was named for French cryptographer Blaise de Vigenère but was actually invented by the Italian cryptographer Giovan Battista Bellaso in 1553. The code was finally cracked by British mathematician and computer pioneer Charles Babbage in 1854.