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I'm a computer programmer and I'm working on a truly unbreakable cypher and I keep going back to a book cypher (each letter of the message is referenced by a page,row,and column number in a random book where both the sender and receiver have identical copies.) In my update we use data files and auto lookup. here is my version:

Step 1) create a book

  • generate a "book" of 5,000,000,000 characters writing the characters randomly. (5 gb)

Step 2) the spys each go there own way

  • both sender and receiver have a copy of the file, but its exists nowhere else. (think 2 raspberry pi's that have never been on the internet)

Step 3) encrypter

 - for each letter of message, pick a random number from 1- 4,500,000,000
 - from that index find a matching character looking forward in the file
 - write to the encrypted file an unsigned 64-bit integer of the sum of 
   the index plus some random large number say for example,715073703555645

Step 4) decrypter

  -reverse the encrypter easy enough for a software program.

If that isn't enough take another random large number, say for example: 36854775 and write that many characters characters out in random before and after the message to the encrypted file.

So how exactly can this be broken?

Jonathan Leslie
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1 Answers1

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From OP's comment:

If all it takes is the key and the plaintext/cihertext, what is guaranteeing that some other program can't repeat the decrypt?

Because the key is long enough, just long enough to make brutal-force attack impossible.

There are some basic models against which a cipher algorithm must be secure, and yours are clearly isn't.

In fact, you've been using "truely unbreakable ciphers" all the time, when you browse a HTTPS website. These websites use TLS or QUIC protocols, which use ciphers to protect both the secrecy and integrity of data exchanged between your computer and the server.

3 of the most popular "truely unbreakable ciphers" are:

  • ChaCha20-Poly1305: a software-friendly design.
  • GCM-AES: a hardware-friendly design.
  • CCM-AES: used most-often in WiFi encryption

A short critique of the OP's proposed cipher.

  1. The codebook is 5GB in size, no practical key exchange algorithm can support that (ECDH are typically no bigger than ~500 bits, finite-field DH can go bigger than that, but isn't in any capacity information-theoretically secure).

  2. How are you supposed to generate that big a key? How are you supposed to pick a character in that codebook? Why can't we use such technique to make a stream-cipher (which is much more efficient than carrying a 5GB code book around)?

DannyNiu
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