Provides access to encryption and decryption of strings according to a variety of classical algorithms. The Solitaire cipher is included for completeness, though it is perhaps not strictly classical.

Currently Implemented

Gotchas

In general, encrypt functions turn text upper-case, while decrypt functions turn text lower-case. This is consistent with convention, but may not be expected.

Code samples

This is the last section of the readme. Nothing appears after this section.

Caesar cipher

Encrypt the text "Hello, World!" with a Caesar offset of 3 (that is, sending 'a' to 'd'):

encrypt_caesar("Hello, World!", 3)
# outputs "khoor, zruog!"

Notice that encrypt_caesar turns everything upper-case, but retains symbols.

Decrypt the same text:

decrypt_caesar("Khoor, Zruog!", 3)
# outputs "hello, world!"

Likewise, decrypt_caesar turns everything lower-case, but retains symbols.

Monoalphabetic cipher

Encrypt the text "Hello, World!" with the same Caesar cipher, but viewed as a monoalphabetic substitution:

encrypt_monoalphabetic("Hello, World!", "DEFGHIJKLMNOPQRSTUVWXYZABC")
# outputs "KHOOR, ZRUOG!"

Decrypt the same text, this time demonstrating the dictionary capability:

decrypt_monoalphabetic("Khoor, Zruog!", "DEFGHIJKLMNOPQRSTUVWXYZABC")
# outputs "hello, world!"

Encrypt using a Dict:

encrypt_monoalphabetic("aBcbDd", Dict{Char, Char}('a' => '5', 'B' => '@', 'b' => 'o'))
# outputs "5@coDd"

Notice that encrypt_monoalphabetic does not convert its input to uppercase when a Dict key is supplied. It simply makes all specified changes, and leaves the rest of the string unchanged.

Vigenère cipher

Encrypt the text "Hello, World!" with a Vigenère cipher of key "ab":

encrypt_vigenere("Hello, World!", "ab")
# outputs "HFLMOXOSLE"

Decrypt the same text with the offsets given as an array:

decrypt_vigenere("HFLMOXOSLE", [0, 1])
# outputs "helloworld"

Notice that the offset 0 corresponds to the key a.

Solitaire cipher

Encrypt the text "Hello, World!" with the Solitaire cipher, key "crypto":

encrypt_solitaire("Hello, World!", "crypto")
# outputs "GRNNQISRYA"

Decrypt text with an initial deck specified:

decrypt_solitaire("EXKYI ZSGEH UNTIQ", collect(1:54))
# outputs "aaaaaaaaaaaaaaa", as per https://www.schneier.com/code/sol-test.txt