- Cryptography: Uses algorithms to produce ciphertext
- Data Encryption Standard: Used to ensure fast, secure encryption
- One-way encryption: Used to encrypt information permanently
- Public-key encryption: Uses two mathematically related keys
- Private-key encryption: Uses a single key to encrypt and decrypt messages
- Cryptographic strength: Used to ensure the difficulty of inverting (or solving) the algorithm

Hieroglyphics (pictograms used in ancient Egypt) inscribed on
a stele in about 3000 B.C. are considered the oldest surviving
example of encryption. Hieroglyphics were long considered impossible
to ever read, but the discovery and study of the Rosetta
Stone in the 19th century was the catalyst that made it possible to
read hieroglyphics.

The “scytale cipher” was a form of encryption used in the city state of Sparta in ancient Greece around the 6th century B.C. It involved the use of a cylinder of a certain diameter around which a parchment strip was wrapped, and the text was written on the parchment strip along the long axis of the cylinder. The method of encryption was designed so that the recipient would be able to read it by wrapping the parchment strip around a cylinder of the same diameter.

Encryption methods like the “scytale cipher” that rely on rearranging the sequence in which characters are read are referred to as “transposition ciphers”. The Caesar cipher, which appeared in the 1st century B.C., was so named because it was frequently used by Julius Caesar, and it is a particularly prominent method of encryption among the great number of encryption methods that emerged during the long history of encryption.

The Caesar cipher method of encryption involves replacing each of the letters of the alphabet in the original text by a letter located a set number of places further down the sequence of the letters in the alphabet of the language. The sender and receiver agree in advance to replace each letter of the alphabet in the text by a letter that is, for example, three letters further down in their alphabet.

Since the Caesar cipher involved the shifting of characters, it is sometimes referred to as a “shift cipher”. If the alphabet consists of 26 letters, texts that have been encrypted by the Caesar cipher can be decrypted by trying 26 patterns. However, instead of simply shifting the characters by a fixed number of places in the alphabet, the sequence can be randomly rearranged, thereby significantly increasing the number of possible patterns (in the example of a 26-letter alphabet: 26 x 25 x 24 x …. = 400,000,0 00,000,000,000,000,000,000 patterns!) and making decryption dramatically more difficult.

The “scytale cipher” was a form of encryption used in the city state of Sparta in ancient Greece around the 6th century B.C. It involved the use of a cylinder of a certain diameter around which a parchment strip was wrapped, and the text was written on the parchment strip along the long axis of the cylinder. The method of encryption was designed so that the recipient would be able to read it by wrapping the parchment strip around a cylinder of the same diameter.

Encryption methods like the “scytale cipher” that rely on rearranging the sequence in which characters are read are referred to as “transposition ciphers”. The Caesar cipher, which appeared in the 1st century B.C., was so named because it was frequently used by Julius Caesar, and it is a particularly prominent method of encryption among the great number of encryption methods that emerged during the long history of encryption.

The Caesar cipher method of encryption involves replacing each of the letters of the alphabet in the original text by a letter located a set number of places further down the sequence of the letters in the alphabet of the language. The sender and receiver agree in advance to replace each letter of the alphabet in the text by a letter that is, for example, three letters further down in their alphabet.

Since the Caesar cipher involved the shifting of characters, it is sometimes referred to as a “shift cipher”. If the alphabet consists of 26 letters, texts that have been encrypted by the Caesar cipher can be decrypted by trying 26 patterns. However, instead of simply shifting the characters by a fixed number of places in the alphabet, the sequence can be randomly rearranged, thereby significantly increasing the number of possible patterns (in the example of a 26-letter alphabet: 26 x 25 x 24 x …. = 400,000,0 00,000,000,000,000,000,000 patterns!) and making decryption dramatically more difficult.