New answers tagged one-time-pad
The question describes a stream cipher with key $S$, using $C_S(R)$ to transmit a random session key $R$, and a keystream (or pad) generated from $R$ using a CSPRNG to encipher the message. This is not an OTP; and contrary to an OTP, it is not secure against a computationally unbounded adversary, who hypothetically, knowing a plaintext/ciphertext pair ...
What you are actually looking for, which is a way to reuse a one-time pad, is not possible. For OTP reuse to be in any way secure, you need an algorithm with enough "complexity" to be a secure cipher (where the "pad" is actually a key). For example, in the comments you raise the idea of including a random number and using the 8-bit CBC that Richie Frame and ...
If you use the OTP it has been used since its invention you will not get away with it. But there is a way that you can beat an attacker (Eve). For the purpose of sending only text we will add a comma, full stop and a space character into an alphabet and randomise it. This will be the initial key that Alice and Bob share. The possible permutations for the ...
Here is how to make a Caesar Shift Cipher work with a One-Time Pad. First you write your message down: "ABCD" Then instead of shifting the alphabet for the whole message. You shift the alphabet for each letter based on a number in your pad. "13, 3, 11, 0" So in this case: For A you shift the alphabet 13 times to get N. B you shift the alphabet 3 ...
What you are essentally describing is a Pseudo-Random Generator in which the base numbers act as the seed. This does not make a good method for generating OTPs because if you know the seed then you just work from there and crack the message.
Letters only allow you to use letters and nothing else. So you would only be able to send a message like this: MEETA GENTV LADAT DINER ATTWO Where as if you use numbers you can send messages with virtually all the different characters you want: Meet Agent Vlad at diner at 2.
The only really effective way of using OTPs is running a Numbers Station. Or at least relaying your message through a Numbers Station. I would check out a document called "Guide to Secure Communications using the One Time Pad" (PDF) for proper CryptSec and OpSec procedures when it comes to using them in the field.
Modern computers are quite fast, and modern cryptographic algorithms are quite efficient. Most computers benchmark hardware accelerated AES in CTR mode well above 1GB/s, which would be a fraction of a millisecond for a 100KiB file. Since the standard system timer generally runs at 1ms intervals, the entire encryption operation ([file data] XOR [AES] XOR ...
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