A brief history of encryption

Encryption, part of the science of cryptography, is the process of transforming information using an algorithm (called a cipher) to make it unreadable to anyone except those possessing a special key to unlock the information. The unlocking process reverses the encryption and is known as decryption. According to a 2007 report by the Computer Security Institute, 71% of the companies surveyed utilize encryption for some of their data in transit while 53% utilized encryption for some of their data in storage.

Encryption, however, is not an idea that was born in the computer age. It has an extensive past and has long been used by militaries, diplomats, and governments to facilitate secret communications. Here is a brief history:


Early encryption was solely concerned with converting messages into unreadable groups of figures to protect the content during the time the message was being carried from one place to another or otherwise in public view. The first approach to cryptography was the simple writing of a message. It worked because most people could not read.

As early as four-thousand years ago, Egyptian scribes decorate the tombs of deceased rulers and kings with irregular hieroglyphs that some experts believe were intended to hide the meaning of the words. Others content they were designed to make the text appear more regal and important.

The ancient Chinese utilized the ideographic nature of their language to hide the meaning of words, but unlike most cryptographic methods, it was used for personal correspondences, and not for military intelligence. Genghis Khan, for example, is not believed to have employed encryption.


The first known encryption device, invented by the Spartans around 400 BC, was a cylinder shaped baton or staff called a scytale. The coding technique consisted of wrapping a strip of leather or parchment around a scytale of a specific diameter. The sender wrote the message down the length of the staff, and then unwrapped the material, resulting in the order of the letters being scrambled. The recipient would then wrap the parchment back around a scytale of the same diameter, and the letters would be in the proper order again.

Caesar cipher

Next came the Caesar cipher which uses a simple system, today known as a substitution cipher, where each letter is shifted a specific number of positions up or down the alphabet. The recipient would decrypt the message by knowing in advance how many positions were needed to reverse the substitution or, probably more often, by trial and error until the correct shift was determined. It is named after Julius Caesar (100 BC–44 BC) because he used it to protect correspondence of military significance, but other substitution ciphers are known to have been used earlier. As a historical note, Caesar used a shift of three, and the second most common shift in ancient times was four.

Another simple substitution cipher is the atbash for the Hebrew alphabet. It is mentioned in the Old Testament Book of Jeremiah and involves replacing the first letter of the alphabet with the last, the second letter with the second last, and continuing in that manner.

More complex ciphers

Simple substitution methods of cryptography were the norm for about one thousand years, but during the Middle Ages turned ineffective as the practice became better known and the population more literate. Aided by advances in mathematics, they were replaced by various random substitution methods as well as an approach known as columnar transposition where messages are written in columns, and then the columns are rearranged.

Italian author and cryptographer Leon Battista Alberti (1404–1472), who has been called the “Father of Western Cryptography”, invented the polyalphabetic substitution method which uses multiple substitution alphabets. A form known as the Vigenère cipher, which employs a series of different Caesar ciphers based on the letters of a keyword, withstood three centuries of attempts to break it. It was still being used by the confederates during the American Civil War, but their messages were regularly cracked by the Union.

A German cryptographer named Johannes Trithemius (1462–1516) wrote Polygraphiae, published in 1518, the first printed book on cryptology. He also invented a steganographic cipher in which each letter was represented by a word taken from a sequence of columns, with the resulting series of words making up prayer.

Cipher wheel

During his term as George Washington’s secretary of state (1790–1793), Thomas Jefferson devised a machine he called a “cipher wheel” consisting of twenty-six cylindrical wooden pieces threaded onto an iron spindle. The letters of the alphabet were inscribed on the edge of each wheel in a random order and turning the wheel scrambled and unscrambled the message. The recipient would decrypt the message with another cipher wheel and trial and error until the correct combination was determined.

Jefferson learned the importance of coded messages while he served as the U.S. minister to France (1784–1789) and found that European postmasters regularly opened and read all letters passing through their command.


The most famous encryption device is ENIGMA, an electro-mechanical rotor cipher machine invented by German engineer Arthur Scherbius at the end of World War I and used by NAZI Germany during World War II. It employs multiple substitution ciphers that rotate iteratively, thereby minimizing the danger of frequency analysis discovering the key. U.S. cryptographers did however break the code during the war, which was a celebrated event for the Allies and affected military intelligence for the remainder of the war.

Modern times

Since the dawn of the computer era, more and more information has become accessible through the internet, both while at rest on servers and while in transmission from one network to another, advancing the needs and requirements of encryption by leaps and bounds. Modern versions now include such enhancements as message integrity checking, identity authentication, and digital signatures.

Today encryption is particularly important for protecting credit card numbers, Social Security numbers, passwords, personal identification numbers (PINs), client lists, business plans, and corporate intelligence. However, for many it is also important for concealing political dissent as well as opposition in the workplace.

Pretty Good Privacy

Today the best known encryption for business and private use is Pretty Good Privacy (PGP) developed by Philip R. “Phil” Zimmermann, Jr. Originally designed as a human rights tool, PGP was published for free on the internet in 1991. It is now owned by PGP Corporation (a part of Symantec).

There is no known method which will allow someone to break PGP encryption, and it has been described by computer security specialist Bruce Schneier as “the closest you’re likely to get to military-grade encryption.” Nonetheless, early versions of PGP were found to have theoretical vulnerabilities, so new editions have been released and development continues.

PGP and similar products follow the OpenPGP standard for encrypting and decrypting data. Defined by the OpenPGP Working Group of the Internet Engineering Task Force (IETF) in Proposed Standard RFC 4880, OpenPGP is today the most widely used email encryption standard in the world.

Advanced Encryption Standard

The most secure encryption at present is recognized as Advanced Encryption Standard (AES) developed by Belgian cryptographers Joan Daemen and Vincent Rijmen. It is based on the Rijndael key schedule which combines multiple transformations. The cipher is described as a symmetric-key algorithm in which the same key is used for both encryption and decryption. AES has been adopted by the U.S. government and is now used worldwide.

Recent concerns

Security uncertainties involving encryption have been recent news items. The most public example occurred in May and June of 2013. Citing documents leaked by former National Security Agency (NSA) contract employee Edward Snowden, U.K. newspaper The Guardian reported that the NSA and its British counterpart, the GCHQ, have cracked ciphers that are widely used to protect online information, including email and other communications, banking and medical records, and corporate data.

For years prior, some have expressed alarm that intelligence and defense agencies throughout the world, including the NSA the U.S. defense department, spend billions of dollars to crack encryption codes.

Security experts nevertheless maintain, if properly implemented and maintained, encryption is still the best practical way to secure data.

The internet is a wonderful resource that allows us to communicate instantly with anyone, virtually anywhere—but it also allows access to cyber criminals and electronic hackers who can steal millions of dollars or wreak havoc in seconds.

It is safest to keep sensitive information on removable storage media such as portable external hard drives and flash memory drives. However, these can be lost, and this is not a useful security solution in many situations.

In a great majority cases the impact of unwanted disclosure of information is negligible—but not always. Do not discount encryption as too difficult, time consuming, or expensive. It is not and in some cases is required by law. There is a good chance one day you will be glad you utilize it.

Leave a Reply