# Questions tagged [one-time-pad]

A cipher which uses a different encryption key every time, as long as the message. The key is XOR'ed with the message to render the cipher text which can then be XOR'ed with the same key to get the plain text.

354 questions
Filter by
Sorted by
Tagged with
432 views

### How can I find the original message of two encrypted (Vernam Cipher) text without the key [duplicate]

Can I get the steps or the solution if possible?
60 views

### How much long the key should be to create a secure encryption with One Time Pad? [closed]

For example would a key with 15 random letters be enough to protect a 52 letters plain text?
52 views

### OTP Random Pad Renewal Without Extending Message [duplicate]

So I recently learned about the concept of a One Time Pad; and I from what I understand it means that if a XOR key is completely random and equal to or longer than the plaintext, it makes it so that ...
129 views

### Why use an OTP if you already have a secure channel

Let's say I have some sensitive information, and I want to encrypt it with a OTP and send it to the FBI or something. Now, in order for the recipient to successfully decrypt the message, he needs to ...
74 views

### Key size of a repeating key XOR-encrypted message using Hamming distance

To find possible key sizes for an encrypted message, I break the message into blocks with length s, ...
767 views

### In laymans terms, what exactly is a “One time pad”?

Background I am an undergraduate novice learning about cryptography. Recently my professor introduced us to the concept of a "One time pad". According to my professor: A one time pad is a cipher ...
73 views

### Infinite one time pads using a pseudorandom hash function [duplicate]

Paul Christiano writes (source): I’ll assume that we have some 256 bit cryptographic hash function F [...] The first important observation is that a 256-bit shared secret allows Alice and Bob to ...
208 views

### One Time Pad Key Distribution

For multiple OTP keys, why not do this: Key = Hash[(EC)DH Shared Secret + Counter] The counter will increase per message, and the output of the hash will be random for each new unique input into it. ...
52 views

### One Time Pad proof for Perfect Secrecy

In the book "Introduction to Cryptography with Coding Theory" by Trappe, in the paragraph about the security of the One Time Pad, is it told that given the set of possible plaintexts $P$, the set of ...
39 views

### decrypting a one-time-pad that outputs 0,1 in preknown probabilities

assuming a two users want to use a one time pad ciphersystem, and they are using a program that was developed by a third party that was supposed to create random undependable bits, but for some reason ...
124 views

### Two possible plaintext's using OTP decryption

I am using this cipher-text c = 04 10 12 00 01 08 67 0A 19 65 0F 03 0A 00 with two possible keys ...
173 views

### What operations provide perfect secrecy other than modulo addition

As far as I know OTP is the only algorithm proven to provide perfect secrecy. It can work with XOR which is addition modulo 2 and obviously it can work with additions modulo N. What other operations ...
69 views

### Running Key Gibbs Sampling

I am trying to implement the algorithm described in this paper. It uses blocked Gibbs sampling to perform a ciphertext-only attack on text encrypted with a running key cipher. However, I am confused ...
239 views

### Using same key twice with Vigenere cipher

Could someone please give a walkthrough of how this works: Decrypting a vigenere cipher with a reused one-time pad. It was never fully answered with the example given in the comment. e.g Plaintext ...
118 views

### Is it possible to use an algorithm to generate an OTP?

I am a software developer, not a cryptologist. I like the idea of perfect secrecy and would like to use a one-time pad (OTP) to encrypt/decrypt files up to, say, 50Mb. Is there a way that I can use ...
695 views

### Why use complex encryption algorithms? [duplicate]

I have recently gotten interested in cryptography, so I looked some things up. I thought, why even use AES or DES or any other complex way for encrypting data when there are far simpler ways, like ...
1k views

### Why do one-time pads not provide message authentication?

It is often said that one-time pads do not provide message authentication. But, if you and I have a one-time symmetric key, and I send you a message, and it is not complete gibberish, is that itself ...
236 views

### How can I quickly generate thousands of letters randomly, and strongly mitigate the risk of any compromise?

I want to generate English letters in a truly random manner without resorting to hand-thrown dice, despite their advantages. Rolling dice would be too slow and tiring as I need four thousand letters. ...
910 views

So I've been reading about cryptography and one-time pads, which seem to provide theoretically perfect secrecy. My question is does any form of technology today allow data to be stored in a practical ...
2k views

### ChaCha20: is this a potentially safe way of using nonce derived from private key if the key/nonce pair is never reused, for a given plaintext?

Note: I realize in ChaCha20 the nonce should be random and unique each time follow certain constraints but am trying to determine whether there could be a safe way to use it just once if other ...
302 views

### Modification of vigenere cipher cryptographically secure?

After looking for ages online for a python implementation of the Vigenere cipher, and finding few, I decided to implement it myself. After ironing out all of the flaws, it's now a working (and secure) ...
118 views

### Why is this OTP decryption wrong? [closed]

i have a problem that goes: ...
61 views

### Partial key reuse in hash for one time pad cipher

There are 2 computers who are going to exchange lots of small packets of data between each other. To generate a shared secret, an elliptic key exchange takes place. If this key is hashed with the ...
211 views

### Can Shannon's proof be applied to all ciphers

I have been studying Shannon's proof of Vernams (1917) unbreakable cipher. Can His proof be applied to positional ciphers?
317 views

### How does bit-wise operation work for encrypting grayscale images? [closed]

How does bit-wise operation work for encrypting grayscale images? In my Khan Academy course they encrypt an image with bitwise_and, ...
219 views

### Robust authentication and integrity for short OTP message

Using any of the wonders of modern cryptographic technology, how is it possible to package a tweet-sized plaintext, which is to be encrypted with a proper one-time pad, to ensure its integrity and ...
100 views

### What encryption shoud I use for single char encryption?

I'm very new to encryption and I wanted to know if it is secure or just possible to use encryption on single chars. I did some research, but nothing to clear and i'm a bit confused. The modes I think ...
308 views

### Are one time pads still secure when using randomly generated words as the pad?

I was researching the US military's DIANA one-time-pad system and came across the following quote purportedly from a former US Special Forces soldier: Special Forces were one of (if not the only) ...
153 views

### Decrypting two ciphertexts using the same key

I'm currently trying to solve an online challenge, where I'm given two ciphertexts, encrypted using a one-time pad and the same key for both messages. The task is to decrypt those messages. What I'm ...
71 views

### Perfect secrecy and known ciphertext length

From what I understand perfect secrecy means that the probability distribution of the messages are independent of the cipertext, right? How can the one time-pad be perfectly secret when the ciphertext ...