**250 one-time-pad questions.**

Firstly some predicates:-
Sufficient hardware generated one time pad key material.
No pad reuse.
Messages of 160 characters length (think Twitter).
28 characters only in use (A-Z, space and full stop ...

I would like an intuitive argument for what goes wrong in the proof that that a one-time pad provides perfect secrecy, if the key $K$ is not chosen uniformly at random from the entire key space.

i'm ask what is the wrong if i used small key multiple times in OTP .?
for example :
key .. . 10 10 10 10 10 10
plain .. 11 01 01 11 01 00
cipher 01 11 11 01 11 10
what can hacker know about ...

When using the PBKDF2, is one taking on significant risk if one chooses to lower the number of iterations and choose to have very long keys?
Can I XOR my message with a a very long key (plain-text ...

I am new to cryptography. My questions is this: I process packets on runtime. I do not have time for advanced encryption or decryption techniques that take a long time.
As far as I know, going with ...

If my plaintext alphabet is {0,1,2}, it has three characters, and I understand why I cannot use a modulus less than 3 (decryption won't work).
My key has 100 different values, {0,1,2 .....99} . ...

Assuming that in the OTP scheme, the key has more values than the alphabet, then: using modular math predetermines that the highest possible value in the ciphertext will reveal the modulus used in ...

I can't understand a question I came across in a course.
You observe three ciphertexts all resulting from encryption of ASCII
plaintexts containing English letters and spaces only, using the
...

Let’s say I have a message $m$ of $n$ bits. And a predetermined pad of $k*n$ bits. And for every bit $b$ of this message $m$, I’m creating random sequence $s$ of $k$ bits.
I also have a predetermined ...

Background: my question at :
My pencil and paper One Time Pad works fine without modular math ...... or does it?
I am trying to understand, from a layman's point of view, how to make the best one ...

I hope, as we know intercepted ciphertext created by One-time pad encryption tells only length of the message, and that is only information attacker can get since this ciphertext its unbreakable to ...

If we're considering Chosen-Plaintext Attack setting, then the adversary has access to the Encryption Oracle right, and we know that OTP is only considered secure if we use the key only once. How ...

With no background in higher math or computer science, I could not quite grasp the value of modular math for simple OTP systems as described in other posts here.
I have an alphabet size of 40 ...

Is there a way to 'mangle' a public data-source (for example, the current date in YYYYMMDD or the top New York Times headline) to form a one-time pad that will sufficiently hide the pad's source?
...

A (synchronous) stream cipher is an algorithm which maps some fixed-length key to an arbitrary-length key-stream (i.e. a sequence of bits): $C : \{0,1\}^k \to \{0,1\}^{\infty}$.
This key-stream is ...

From WAR10CK here:
If I actually do create a machine using RC4 or AES-CTR and have a TRNG continually feed it a constant steady stream of random bits. Provided that the stream of bits is purged ...

In one time pad cipherText1 xor cipherText2 == plainText1 xor plainText2 so is it possible to find out key by 2 cipherText and plainText's xor?

I have heard some people say that the Poly1305 authenticator is a "nuclear" MAC i.e. it is information-theoretically secure. After reading the paper I see it is based on the Wegman-Carter MAC which is ...

If we were define such a cipher:
A reversible function that would accept a message $M$ and an initialization vector $\text{IV}_1$ $\operatorname{map}(\text{IV}_1, M)$ which can map an input $M$ to a ...

Instead of generating the random key for the one time pad cipher over and over again, is there a mathematical formula that allows you to switch the key to a new key? The new key must be as random and ...

It is known that One-Time Pad(OTP)s are theoretically unbreakable but impractical for use because of the size of the key length. But what if multiple encryption is used? Not to encrypt the first ...

I want to generate truly random one time pad as fast as possible but without the use of any electrical or any other complicated device. What is the fastest way to do that?

Suppose I have the message $m_1 = \sf{i\ like\ dogs}$.
Suppose its one-time pad encryption with key $k$ is a given hexadecimal string of 22 characters.
How would I encrypt a message $m_2 = \sf{i\ ...

I computed $\Pr[\mathsf{CT} = 1] = \Pr[\mathsf{CT} = 2] = \Pr[\mathsf{CT} = 4] = 2/9$ and $\Pr[\mathsf{CT} = 3] = 1/3$.
When I calculate the first entry in the table, I get 1/2 not 1/9. Is my ...

Consider the one time pad with messages and keystreams in binary strings. Suppose that the system is used erroneously, so that two messages have been encrypted using the same key. What information can ...

Let say
$K_{0} = \left \{ 0,1\right \}^n$
$K_{1} = K=\left \{ 0,1\right \}^n$ \ $0^n$
$[b\leftarrow \left \{0,1 \right\}, k \leftarrow K_{b}:b=1|k \neq 0^n]$ --- (1)
Key is chosen using ...

It's a common adage that for a perfectly secret one time pad, length(key) >= length(message) must hold. But that's wrong isn't it? At least very sloppy maths. Isn't the strict mathematical ...

I understand why |one-time pad|=|message| using a normal one-time pad, but I don't understand why for perfect secrecy it must alway be that |key|>|all messages exchanged|.
What if, for example, I had ...

I'm learning about basic cryptography at university, and I'm reading that reusing a key in a stream cipher such as the Vernam cipher compromises its security.
Because XOR is a reversible operation, ...

After reading up on the one-time pad (OTP) encryption method, I could see how it would offer unbreakable encryption if used properly.
Moreover, I looked at how the OTP could be broken if the OTP-key ...

In the 20th century, it was common for various intelligence agencies and military organizations to use ciphering machines and one-time pads.
However, no source I've seen ever mentions the process of ...

I have a key for a one-time pad. Its length is 512, and I have a message to encrypt whose length is 600. Can I reuse the first 88 chars of the key to encrypt the end of the message?
The key is still ...

I was playing with the Vernam cipher on some online converter.
But when I tried to encrypt my message string with numbers, it remained unchanged.
Moreover, it was ignoring numbers and was encrypting ...

By profession I’m a programmer. I don’t know a lot about how cryptographic algorithms are implemented, or even where I’d start, and I don’t know about cryptanalysis, but as I work in Blockchain ...

The symmetric cryptosystem one-time pad (OTP) seems to be very beautiful since it is perfectly secret according to Shannon. Many books, however, point out the main drawback: one must create a secret ...

I have just read about the perfect security of an OTP encryption and what came to my mind was that what if the Pad used for encryption/decryption did not have to be transported separately from the ...

Can anyone explain to me what the following means in relation to one time pad security? It's from the book 'Serious Cryptography: A Practical Introduction' and my logic knowledge seems to have lost ...

I would like to ask for a clear (but maybe not so deep) explanation of what the term "perfect secrecy" means.
As far as I have researched and understood, it has to do with probabilities of assuming ...

While looking at this question I discovered the following here (question 5), and wanted to ask it as a separate question.
Alice knows that she will want to send a single 128-bit message to Bob
...

In my assignment there is a bonus question:
It asks me to decrypt a file which has been encrypted using an One-Time-Pad.
But the ciphertext seems to contain english word fragments and other parts ...

According to Wikipedia the One Time Pad Cipher is unbreakable. On the Wikipedia page it explains how to perform this simple encryption process by hand. For the encryption it adds (+) the message and ...

I'm setting up some external hardware for OTP encryption to take care of all the issues that can arise with key storage, re-use etc. I'm using the ISAAC secure PRNG to get my stream of numbers which ...

I was reading about how a one time pad output can be changed by a third party without the receiving person realising. Surely the output at the other end would be garbage? Also, could you not ...

Considering that a PKI has already been established, why can't we use RSA to send the One Time Pad instead of using AES?
It makes sense to me since:
A trusts the CA which is providing the identity ...

- encryption
- cryptanalysis
- perfect-secrecy
- xor
- key-reuse
- stream-cipher
- hash
- random-number-generator
- keys
- randomness
- algorithm-design
- symmetric
- mac
- entropy
- aes
- modular-arithmetic
- rsa
- block-cipher
- authentication
- brute-force-attack
- chosen-plaintext-attack
- vigenere
- information-theory
- provable-security
- attack

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