# Homer – New Homophonic Substitution Cipher

Cryptography in digital technologies is needed as a tool to protect confidential data. By 2022, many cryptographic algorithms have been developed and are constantly being improved.

I suggest turning to one of the very first encryption methods – substitution method… In the 21st century, this method may seem unreliable.

My idea is based on homophonic substitution cipher… The principle behind this idea is replacing all bytes File A the position numbers of these bytes in file BReceived file C is an encrypted file A (Fig. 1).

Now in order to restore file A, it is enough to replace the position numbers in file C bytes from File B (Fig. 2).

To implement this idea, I have developed the “Homer” application in Python.

Let’s take a look at the principle of encryption in the Homer app.

Reviewed earlier file A we consider it secret. File B is our “map” (a prerequisite for file B is the presence of all bytes from file A in it)

For encryption File A File B replace the bytes in file A the position numbers of these bytes in file B… Moreover, when repeating the same byte in file A trying to find the number of the next position of this byte in file B

For example, let’s encode the secret file A with content “WWW “ by using file-map B with content “The World Wide Web” (Fig. 3).

For decryption File C read the bytes from the map file at the positions specified in file-map B (Fig. 4)

As a result, we get back the original file A

At the moment, the main problem of implementation is the low speed of encryption / decryption processes. But the ability to use almost any file as a map, without losing reliability, gives a huge advantage over other algorithms. You can use a photo, media file, or any other file as a map and keep it publicly available. No one will suspect that it can be used as a decryption card.

You can post a new photo on Instagram, your friends and colleagues will like and comment on it, but only you will know that it can be used to decrypt other files.

At the same time, without knowing this file, it is unrealistic to crack the original one! Don’t believe me? Then tell me what’s in this file?

The algorithm will be improved. I would be glad to receive constructive suggestions and criticism. They will help me develop the idea.

You can find the source code of the Homer app in my repositories on github.