Ancient societies used a variety of secure communication techniques, including secret alphabets and straightforward transposition and substitution cyphers. These techniques are traced back to the history of cryptography. Polyalphabetic cyphers, which used multiple alphabets to encrypt messages, were one of the message-encoding systems created during the Middle Ages.
Cryptography was a crucial aspect of the wars in both World Wars I and II. Both the Allies and the Central Powers used different encryption techniques to protect their communications during World War One. Germans were especially adept at this, encrypting their communications with a device known as the "SZ" (short for Schlüsselzusatz, or "cypher attachment"). The Zimmermann Telegram, which was instrumental in bringing the United States into the conflict, was one of the German cyphers that the Allies were able to crack.
Even more extensive and complex use of cryptography was made during World War II. The Allies made major efforts to decipher the code used by the Germans to encrypt their messages using the Enigma machine. The work carried out at Bletchley Park, where Alan Turing and a group of codebreakers were able to decipher the Enigma code, is the most well-known of these initiatives. As a result of the Allies being able to intercept and decrypt German military communications, this was a crucial turning point in the conflict.
The Japanese also used complex encryption methods, particularly the Purple machine, used by the Imperial Japanese Navy, which was also broken by the US.
The Allies, on the other hand, employed a variety of encryption techniques, including the Typex machine, which the British military employed, and the SIGABA machine, which the US military utilized. Both of these machines proved to be extremely safe.
Overall, the use of cryptography in both World Wars had a substantial impact on how the wars turned out, with the ability to decipher enemy codes frequently giving the decryption side a vital advantage.
Computer innovation in the digital era has produced complex encryption algorithms like RSA and AES, which are widely used to protect data in computer systems and networks. Asymmetric cryptography, also referred to as public-key cryptography, was created in the 1970s and enables secure transmission without the need for prior secret key exchange.
In recent years, new cryptographic techniques have been created that offer even higher levels of security. These include elliptic curve cryptography and quantum cryptography. These techniques were made possible by the widespread use of the internet and the growing significance of electronic communications.