A Go implementation of the simple Autokey cipher. Autokey has some useful characteristics: the output is the same length as the input and looks like the input was merely jumbled as it uses the same alphabet as the input:
- Input:
all our words from loose using have lost their edge. - Output:
kbu cjd hprjy qmud ilujd xpxkq xxsw hvng zgksj nqwa.
This is similar to and based on the stream cipher implementation at https://github.com/hex7c0/autokey but restricts the input and output to a given alphabet. This means you can let spaces, punctuation, and other characters go through the algorithm with no change.
To install:
go get github.com/allenluce/autokey
package main
import "github.com/allenluce/autokey"
const Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
func main() {
// The key does not have to be chosen from the alphabet.
akey := autokey.NewAutoKey("MyKeyIsThis", Alphabet, 2)
input := "Something very important!";
cipherText := akey.Encode(input)
println(cipherText)
recoveredText := akey.Decode(cipherText)
println(recoveredText)
}NewAutoKey takes a key and an alphabet as the first two
arguments. The key should consist of characters from the given
alphabet.
The third argument to NewAutoKey is a seed length. When encoding
plaintext that consists of many smaller strings with a very high
number of duplicates, the regular Autokey cipher will spit out many
duplicates on its own. This could allow a viewer to infer values based
on the frequency of the duplicated strings.
Using a seed makes this more difficult. A new seed is determined
randomly for each call to Encode() and then tacked on the front of
the emitted string. This means that output will be larger than input.
A 0 may be given as the seed length to use the regular Autokey algorithm with no random seed.
Autokey is a very old cipher with known vulnerabilities and is not as secure as modern encryption systems. You should consider this algorithm as a slightly better alternative to ROT13 or base64 for obfuscating text.