Editing Cipher (section)

===Historical===
[[File:Caesar cipher left shift of 3.svg|thumb|Visual representation of how Caesar's Cipher works.]]
The [[Caesar cipher|Caesar Cipher]] is one of the earliest known cryptographic systems. Julius Caesar used a cipher that shifts the letters in the alphabet in place by three and wrapping the remaining letters to the front to write to Marcus Tullius Cicero in approximately 50 BC.{{cn|date=March 2023}}

Historical pen and paper ciphers used in the past are sometimes known as [[classical cipher]]s. They include simple [[substitution cipher]]s (such as [[ROT13]]) and [[transposition cipher]]s (such as a [[Rail Fence Cipher]]). For example, "GOOD DOG" can be encrypted as "PLLX XLP" where "L" substitutes for "O", "P" for "G", and "X" for "D" in the message.  Transposition of the letters "GOOD DOG" can result in "DGOGDOO". These simple ciphers and examples are easy to crack, even without plaintext-ciphertext pairs.<ref>{{Cite journal|last=Saltzman|first=Benjamin A.|title=Vt hkskdkxt: Early Medieval Cryptography, Textual Errors, and Scribal Agency (Speculum, forthcoming)|url=https://www.academia.edu/35034685|journal=Speculum|year=2018 |volume=93|issue=4|page=975|doi=10.1086/698861 |jstor=26584834 |s2cid=165362817|language=en}}</ref><ref>{{Cite book |last=Janeczko |first=Paul B |title=Top Secret |year=2004}}</ref>

In the 1640s, the Parliamentarian commander, [[Edward Montagu, 2nd Earl of Manchester]], developed ciphers to send coded messages to his allies during the [[English Civil War]].<ref>{{cite web |title=English Civil War cipher belonging to Cromwell ally goes on display |url=https://the-past.com/news/english-civil-war-cipher-belonging-to-cromwell-ally-goes-on-display/ |website=The Past |date=12 July 2023 |access-date=4 August 2023}}</ref> The English theologian John Wilkins published a book in 1641 titled "Mercury, or The Secret and Swift Messenger" and described a musical cipher wherein letters of the alphabet were substituted for music notes.<ref>{{cite web |title=Types of Ciphers |url=https://www.audiocipher.com/post/types-of-ciphers |website=AudioCipher |date=26 February 2025 |access-date=14 March 2025}}</ref><ref>{{cite web |title=Mercury: Or the Secret and Swift Messenger |url=https://www.lybrary.com/mercury-or-the-secret-and-swift-messenger-p-5897.html |website=Lybrary |access-date=14 March 2025}}</ref> This species of melodic cipher was depicted in greater detail by author Abraham Rees in his book Cyclopædia (1778). <ref>{{cite web |title=Cyclopaedia |url=https://archive.org/details/cyclopaediaoruni08rees |website=Internet Archive |access-date=14 March 2025}}</ref>

Simple ciphers were replaced by [[polyalphabetic substitution]] ciphers (such as the [[Vigenère cipher|Vigenère]]) which changed the substitution alphabet for every letter.  For example, "GOOD DOG" can be encrypted as "PLSX TWF" where "L", "S", and "W" substitute for "O".  With even a small amount of known or estimated plaintext, simple polyalphabetic substitution ciphers and letter transposition ciphers designed for pen and paper encryption are easy to crack.<ref>{{citation|first=Douglas R.|last=Stinson|author-link = Doug Stinson|title=Cryptogtaphy / Theory and Practice|year=1995|publisher=CRC Press|isbn=0-8493-8521-0|page=45}}</ref> It is possible to create a secure pen and paper cipher based on a [[one-time pad]], but these have other disadvantages.

During the early twentieth century, electro-mechanical machines were invented to do encryption and decryption using transposition, polyalphabetic substitution, and a kind of "additive" substitution.  In [[rotor machine]]s, several rotor disks provided polyalphabetic substitution, while plug boards provided another substitution. Keys were easily changed by changing the rotor disks and the plugboard wires. Although these encryption methods were more complex than previous schemes and required machines to encrypt and decrypt, other machines such as the British [[Bombe]] were invented to crack these encryption methods.