Computer Encryption History

A Complete History of Encryption


Today, we understand computer encryption as a critical part of data protection. For instance, by law, registered public health organizations must meet the Federal Information Processing Standard (FIPS).

FIPS requires these groups to encrypt stored confidential files. Confidential files could be anything from patient health information (PHI) to classified government documents.

And encryption isn't just for large organizations. Every day, people connect to the internet via Wi-Fi. Contemporary Wi-Fi devices use the WPA3 protocol.

This protocol encompasses a standard set of security tools. One tool is GCMP-256 encryption, which protects data in transit. GCMP-256 encryption improves on the previous standard data security tool, 128-bit encryption. 

FIPS and WPA3 are standards of the internet age. Yet, humans have been using and improving encryption methods for almost 4000 years! Today, we'll uncover the history of encryption, from Mesopotamian tablets to modern keys, so be sure to keep reading. 

Encryption Key Terms Defined

Before we jump into the complete history of encryption, let's clarify a few key terms. First, let's unpack what "encryption" means, and how it works. 

Since we typically talk about encryption in the context of cybersecurity, many people's mental definition of "encryption" is narrower than the true scope of the word. 

What is Encryption?

Encryption is a method of protecting information. To use this method, you take information (like a written message or bits of data) and convert it into a code. Cryptologists call these codes "ciphers."

If someone intercepts the encrypted message, they can't read it. The cipher makes it seem like gibberish.  

The intended recipient of the message will have a key. The key decrypts the code. The recipient can read the message once it's decrypted.

What is an Encrypted Message?

An encrypted message is disguised information. If the information in a message is valuable, someone else might attempt to steal it. With encryption, the message is useless to anyone other than the intended recipient. 

A message could be a network packet. Computers connected to a network communicate to one another via packets. Packets contain information, and instructions on how to deliver the information. 

At the same time, any type of message written by humans can be encrypted. You can disguise spreadsheets, recipes, and even diary entries with a cipher.  

What is a Cipher?

A cipher is a code that disguises a message. Specifically, it uses a method to substitute each sub-unit of information with a different unit, according to a complex set of rules. 

A typical cipher substitutes each letter in a document with different letters—or with numbers or symbols. In a computer network, a cipher substitutes bits of information in a data packet with different bits. 

Laypeople use the terms "cipher" and "code" interchangeably. But, in cryptography, a cipher is distinct from a code.

Cipher vs. Code

Codes are more akin to translation than disguise. Morse code, for example, translates letters and words into dot-and-dash symbols. Long words and phrases are given standard abbreviations (think "S.O.S" for "save our ship.)

The purpose of Morse code is not to hide information. Its purpose was to transmit information effectively via telegraph. 

Cipher: Verb Form and Synonyms

The noun form of "cipher" refers to the algorithmic substitution method. The verb form of "cipher" is the act of encrypting information.

A general might tell a soldier, "you must cipher the message before you deliver it." Cipher is sometimes spelled "cypher."

What Does Encrypted Mean?

Encrypt is synonymous with the verb form of cipher. It's the act of encoding a message using a substitution method.

So, "encrypted" describes a set of information that's been disguised. An encrypted message is unreadable. 

Encryption: Ancient Origins

Ancient encryption technologies pre-date the English alphabet. People in ancient civilizations carved ciphers out of wood or molded them from clay. 

Some ancient ciphers were used to deliver messages in war. Others had religious significance. And, in at least one case, an artist used a cipher to protect a secret recipe—long before patents existed. 

Pre-Cryptography in Ancient Egypt

In the tomb of Khunumhotep II, archeologists found unusual hieroglyphs. The pictorial writing was incomplete, and many of the hieroglyphs were drawn in reverse. 

The hieroglyphs correlated to passages in The Book of the Dead. Yet, they were disordered. Egyptologists speculate the writing was a type of spell that the Pharo believed he would finish in the afterlife.

Many of the tombs in this region, Unas, featured transmuted or altered hieroglyphs. But, this was not a true cipher intended to hide information. Instead, it was meant to guide the dead through the afterlife. 

Cuneiform Cipher in Ancient Mesopotamia

Archaeologists discovered the earliest known true cipher in ancient Mesopotamia. At some point around 1500 BC, a Mesopotamian artist created a new form of pottery glaze. 

The artist documented the glaze recipe on a cuneiform tablet. Then, he concealed the recipe with a substitution code. This early cipher swapped out letters in the cuneiform script.

This lets the artist remember the recipe while disguising it from rivals. 

Scytale Cipher in Ancient Greece

This old-school encryptor might not actually be a cipher. A scytale cipher is an encrypting tool. It was used by ancient Greeks, specifically Spartans, in war.

The scytale is a cylinder that one wraps parchment or leather around. The sender writes the message straight across the wound parchment.

When the parchment is unwound, the message is interspersed throughout the parchment. The recipient must wind the paper correctly on their own scytale to decrypt the method.

Caesar Cipher in Ancient Rome

The Caesar cipher was an early substitution encryption tool. Some historians call it the "Caesar Shift."

The Caeser cipher sets two alphabets parallel. The two alphabets' letters are in a different order from one another.

To encrypt a message, the writer would shift the cipher by a set degree. Then, they'd write the letter in the parallel alphabet that's across from the intended letter. 

To decrypt a message, the recipient must know the shift key. That is, how many degrees they should shift the cipher by to reveal the intended letters.  

Atbash Cipher in Ancient Hebrew

The Atbash Cipher was a substitution cipher. It worked similarly to the Caesar cipher. But, it was developed for the Hebrew alphabet. 

Unlike the Caesar cipher, the Atbash had no shift key. Letters were always converted to the same numbers.

This provides very little protection. Some historians believe the Atbash cipher was only used for religious rituals, not encryption. 

Encryption in the Middle Ages

Different cultures started developing encryption technology in earnest in the Middle Ages. The Golden Age of the Arab world brought mathematical discoveries to light. 

Historians refer to this period in Europe as the "Dark Ages." Yet, encryption technology evolved there too. In fact, encryption methods catalyzed crucial political revolutions on the continent. 

Book of Cryptographic Messages (717-786 AD)

The mathematician Al-Khalil created The Book of Cryptographic Messages in the 8th century. This book listed all possible Arabic words. 

Khalil used methodical permutations and combinations to compose the complete list. He also documented his cryptographic methods.

Al-Kindi Invents Frequency Analysis Technique (~800 AD)

The Book of Cryptographic Messages influenced thinkers throughout the Golden Age. The mathematician Al-Kindi developed his theories from this text. Eventually, Al-Kindi created the frequency analysis technique.

The frequency analysis technique would stand as the greater advancement in codebreaking until World War II. Yet, Al-Kindi's original technique worked best on monoalphabetic substitution ciphers.

Later, the mathematician Ibn Adlan expanded the technique. With Adlan's contributions, frequency analysis became a plausible means to decrypt polyalphabetic ciphers.

Subh al-a 'sha Encyclopedia (1355-1418 AD)

By the mid-1300s, people sought standards of knowledge. Ahmad al-Qalqashandi wrote the first encyclopedia of the Arab world.

The Subh al-a 'sha included sections on cryptography. This is the earliest remaining record of both homophonic substitution and transposition ciphers. It also includes expository writing on cryptanalysis.  

Duke of Mantua Creates Homophonic Substitution Cipher (~1400 AD)

Homophonic substitution combats frequency analysis.

Prior ciphers largely disguised each letter of the alphabet with one distinct symbol per letter. Frequency analysis cracks these monoalphabetic ciphers.

Decrypters note how frequently each symbol appears in the text. Then, they look at tables showing which letters appear that frequently in language. Books like Al-Kindi's serve as the basis for this technique. 

Homophonic substitution fights this method. The Duke of Mantua's cipher assigns more symbols to more frequent letters. Thus, all symbols in the ciphered message appear with the same degree of frequency. 

The homophonic cipher includes monoalphabetic and polyalphabetic elements. 

Leon Battisti Alberti Describes Polyalphabetic Cipher (1467 AD)

Leon Battisti Alberti described the concept of a polyalphabetic cipher. A polyalphabetic cipher uses more than two alphabets to encrypt messages. 

Alberti's described how this type of cipher could work, in theory. But, he did not create one to use himself.  

Inventing Cipher Disks

Alberti invented cipher disks in 1470. Cipher disks include two stacked, circular plates. Alphabets are printed on the plates' circumferences.

The bottom disk is stationary. You can turn the second disk. The cipher key tells the recipient how many degrees to turn the disk.

It also notes whether to turn it more than once. After the disks are in the right position, you can decrypt a message letter-by-letter.   

Johannes Thrithemius Publishes Steganographia (1499 AD)

Johannes Trithemius was a German Benedictine abbot. He published Steganographia in 1499. 

Steganographia appeared to be a three-volume book about magic. But, it was actually about cryptography and steganography. Steganography is the practice of hiding a message in an image.

Steganographia depicts a tabula recta. This illustration is a square grid of alphabets. Readers could use it to create new polyalphabetic ciphers.

The text enabled people to create new, complex polyalphabetic ciphers. The French cryptographer Blaise de Vigenère used Steganographia to develop the Vigenère cipher.

Revolutions Catalyze Cipher Evolution In Europe

The Medieval era fostered political and religious revolutions. Cipher development spread throughout Italy. Encrypting became standard practice to keep messages from Papal leaders.

Most ciphers were still unsophisticated at this point. But, as the revolution spread, so did cipher technology. 

Post-Medieval Encryption: 1500-1900

By the end of the Italian Renaissance, people used ciphers worldwide. Message and data encryption became critical military tools.

And, inventions like the printing press made writing available to entire cultures for the first time. Between technology and increased global trade, encryption history gets interesting.  

Japan's Uesugi Clan Develops Polybius Square Cipher (1500 AD)

The Uesugi clan was a powerful Japanese samurai clan. They held power from the 14th to the 17th century.

Uesugi members communicated discreetly with encrypted messages. They used a Polybius square cipher to disguise their words. 

The square used the Iroha version of the Japanese alphabet. This alphabet has forty-eight letters.

The Polybius square was a 7x7 grid. They filled all squares with letters, except one. Then, they wrote the last fourteen letters of the "Iroha" poem in the square's header and sidebar. 

They created keys from these headings.  

Baconian Cipher in England (1605 AD)

Sir Francis Bacon was an English philosopher. He developed a unique steganographic cipher. Bacon's cipher concealed a message within the text, but didn't change the message's content. 

Bacon's cipher requires a printing press. To conceal messages, he used a bilateral alphabet. Then, he used two different typefaces to disguise the message.

To use Bacon's cipher, the writer needs to write the real message and a false message. Both messages need the same number of characters. 

The French Military's Great Cipher (1627-1811 AD)

Antoine Rossignol was the chief cryptographer of King Loius XIV. He developed the Great Cipher. The French Military used the cipher for over a century.

The Great Cipher was said to be unbreakable. Decrypting ciphered messages required elaborate code sheets. Over 500 number sets would substitute letters, syllables, and words.  

Ultimately, Étienne Bazeries cracked the code in 1811. Bazeries later published the groundbreaking cryptography book, Secret Ciphers Unveiled.

Charles Wheatstone Develops Playfair Cipher (1853)

The Playfair cipher was the first diagram substitution cipher. The Playfair cipher substitutes letter pairs instead of individual letters.

There are 600 possible bigrams (letter pairs). As such, the Playfair cipher demands a longer ciphertext than previous ciphers.

It's challenging to use frequency analysis to decrypt bigrams. But, it's not impossible. So, the British military only used the Playfair cipher to deliver timely messages. 

Friedrich Kasiski's Cryptanalysis Method (1863 AD)

Friedrich Kasiski was a German officer. He developed a unique method to tackle polyalphabetic ciphers. 

Kasiski looked for strings of repeated symbols in the ciphertext. He predicted distances between strings indicated how many multiples there were of the keyword in the original text. 

The string-based attack is incredibly challenging for humans. But, in later years, computer scientists used Kasiski's method to develop data decryption processes. 

Breaking the Vigenère Cipher

Friedrich Kasiski also cracked the Vigenère cipher. The Vigenère cipher was the first auto-key cipher. That is, the key was the original message itself. 

It was easy for intended recipients to decipher Vigenère-coded messages. They simply needed cipher disks. Without the disks, though, Vigenère ciphers seemed unbreakable. 

To break the Vigenère cipher, Kasiski used a string-based approach. He also used superimposition.

Kasiski layered copies of the message atop one another in a stack. Then, he searched for string patterns in columns of letters, mirrored through each copy.

Encryption Advances of World War I (1914-1918)

The first world war accelerated encryption evolution.

The rate of technological breakthroughs is hard to cover in just one article. Historians have dedicated entire books to the subject.

One worthwhile read is Before Enigma, by David Boyle. Boyle covers the cryptological evolution catalyzed in Room 40. Room 40 was the cryptoanalysis wing of Britain's military. 

In the four years of World War I, cryptographers innovated across the board. They began to create ciphers based on Native American languages. And, they invented two key technologies: the electric rotor cipher and the one-time pad.

The one-time pad was the only, truly unbreakable cipher. It used teletype and paper tape. Crucially, the pad requires a pre-shared decryption key that's at least as long as the message.

Once the key is used, it's destroyed.

The Herben Rotor machine was a groundbreaking mechanical cipher. It elevated cipher disk technology to extraordinary, mechanical complexity.

The rotor machine incorporated a typewriter. And, it enabled the typist to scramble the message according to a complex mechanism with multiple rotations. 

These breakthroughs laid the groundwork for encryption in World War II. 

Encryption in World War II (1939-1945)

Accelerating encryption was critical to winning World War II. Electromechanical cipher machines were used by every nation.

Every military sought to improve cipher design. At the same time, it was critical to improve cipher analysis strategies. 

For the Allies, cryptography work often focused on breaking the Enigma code.  


The Enigma machine was a cipher device. Nazi Germany used it extensively during the war. The Polish cryptanalyst Marian Rajewski used permutations theory to damage the plugboard on the machine's keys. 

This enabled Poland to build a competing machine. The Polish Cipher Bureau collaborated with British cryptologists. Alan Turing was one member.

Together, they advanced Enigma decrypting technology. 

The Venona Project

The Venona Project was the United States' counterintelligence program. It developed key decryption technologies. 

The Venona Project integrated traffic analysis with other cryptoanalysis techniques. Traffic analysis looks at patterns in overall communication. This begets useful information, even when one can't decrypt the message content. 

Breakthroughs at Bletchley Park 

British cryptographers advanced the field at Bletchley Park. Women played an important role. Britain recruited over 11,000 women as operators.

Bletchley Park codebreakers decrypted Naval Cipher No. 3. This gave Britain a critical, tactical advantage. Ultimately, these breakthroughs turned the tide of the war. 

Postwar Encryption Advances (1946-1999)

Encryption technology progressed further after World War II. The cold war between the United States and the Soviet Union spurred some of this innovation.

In other cases, encryption accelerated in the private sector. As economies boomed, non-government entities had funds to invest in new security technologies. 

Claude Shannon Publishes Mathematical Cryptography Theory (1949)

In 1949, mathematician Claude Shannon published a new theory of cryptography. He applied statistical models to the practice.

Shannon aimed to improve security and authenticity. His mathematical theory of communication articulated a new scientific praxis for cryptographers. 

These works influenced cryptographers for decades. Crucially, it accelerated the development of the public key. 

IBM Develops Data Encryption Standard (1975)

IBM aimed to develop secure electronic communication for businesses. So, in 1975, it proposed the Data Encryption Standard. 

Federal agencies supported the DES. It became the first publically accessible cipher. The standards' release triggered a new wave of interest in cryptology. 

Diffie-Hellman Key Exchange (1976)

The Diffie-Hellman key exchange was a cryptographic key exchange method. It was the first protocol to standardize security measures for such an exchange.

This method uses both a public key and a private key. It empowered two individuals, who had never met, to establish a joint key. It works even when they establish the key over an insecure channel.

The Diffie-Hellman key exchange was a critical tool. It was the first method to send data across networks safely. It's the precursor to all contemporary encryption software.

USA Adopts Federal Information Processing Standard (1977)

In 1997, the United States adopted the Federal Information Processing Standard (FIPS). Engineers initially used DES to develop FIPS.

This standard mandates communications security measures for all government departments. FIPS is continually updated.

Phil Zimmerman Releases PGP Cryptosystem (1991)

Some government officials wanted to keep encryption technology from the public. The computer scientist Phil Zimmerman opposed this view. 

Zimmerman wrote and released "Pretty Good Privacy" in 1991. The PGP cryptosystem was free to the public. It had no known backdoors, a development that, at the time, existed in a legal gray area. 

The Justice Department investigated Zimmerman for allegedly violating export laws. But, it dropped the charges. PGP became an open internet standard.

OpenPGP is still in use today. 

Computer Encryption in the 21st Century

Encryption technology is still developing, even now. In 2001, the Advanced Encryption Standard replaced DES. New standards use keys with more characters, which are stronger against brute force attacks. 

In 2003, the Wi-Fi Alliance developed WPA. WPA, and its subsequent iterations, use new cryptography methods to keep data secure in transit. 


In 2010, companies began to provide high-speed internet through fiber-optic cables in the United States. These cables transfer data at near-light speeds. Yet, the new mode of transit poses new security risks.

As of today, engineers are developing new encryption methods to protect high-speed data in transit. Some designers think new encryption technology should take advantage of quantum physics.  

In 2018, Verizon launched the first 5G network in the U.S. It also introduced 256-bit roaming encryption, making it safe enough to—potentially—run the first 5G fixed wireless internet option in rural regions.

As communication changes, so does communication security. What will we build next?

The Future of Encryption Starts Here

At SecPoint, we believe it's important to study the past if we want to build the future. The developments that led to computer encryption today can inspire the breakthroughs of tomorrow.

We're ready to bring the next stage of encryption to you. Our cybersecurity teams build groundbreaking solutions to evolving threats.

If you want to learn how next-gen security can keep your data safe, contact us. We'll find the best-fit software for your security needs.