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.

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Is the One-Time-Pad IND-CCA2 Secure?

I know that the OTP is considered to have perfect secrecy, but I haven't seen anything about its security against chosen ciphertext attacks, and I was wondering about its secrecy in this regard. My ...
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If a stream cipher uses a truly random, injective function, can we get rid of epsilon?

Imagine an encryption scheme defined as follows for a fixed $|k|$ and $|m| > |k|$: $K = \{0, 1\}^{|k|}$ $K' = M = C = \{0, 1\}^{|m|}$ $G: K \rightarrow K'$ is a truly random injective function $E(...
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Does XOR of message $m$ with $\mathrm{Enc}$ leak any information?

Let's suppose that $(G,D,E)$ is a secure encryption scheme, that is, for any polynomial $p(n)$ and any sequence of messages $\{a_{n}\},\;\{b_{n}\}$ of length $p(n)$ $E(k,a_{n})$ and $E(k,b_{n})$ are ...
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Proving if two samples hides a value?

Given two values $r'-r \mod q$ $i - r \mod q$ Where $r',r$ sampled randomly from $Z_q$ while i is pick arbitrarily from $Z_q$ and a secret Can we claim that this hides $i$? Here is my sketch: ...
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Advantages of AES vs XOR on a plain text file

Currently, I am using AES-GCM to encode and decode a plain text file. The key is derived from a plain text password using PBKDF2 and a random salt with SHA-256. However, I have been thinking and came ...
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Perfect Secrecy other than One-time Pad

The most known example cipher reaching perfect secrecy is One-time Pad, which employs modulus addition for encryption and decryption. Is there any other well-known cipher no less practical than OTP ...
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Instead of asymetric encryption, why not use two One-time pad? [duplicate]

Why is the following protocol never used to share a symetric key between two parties ? ⊕ is the XOR operation. Alice has M and wants to send it to Bob. Alice generates K₁ randomly. Bob generates K₂ ...
Pierromer's user avatar
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Are the null bytes produced by a True Random Number Generator a security issue when using it as a source of entropy for keys in One-time pad?

I can see that True Random Number Generators can produce some null bytes, after some megabytes of data, even 2 consecutive null bytes are produced: ...
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May I use the same One-time pad key two times if I encrypt it with a block cipher using two different block cipher keys?

Let's suppose I have two 2GiB files and I want to encrypt them using One-time pad (Vernam cipher), but I don't want to store two big keys. May I use only one key for the two files if I encrypt the One-...
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If I hash different seeds with same size of hash output and XOR on plaintext, is it secure as One-time pad?

Let's suppose I take 1MiB of truly random data and split in pieces (seeds) of 32-bytes (256-bits), so I hash each seed with a hash function with the same output digest size (32-bytes/256-bits) and XOR ...
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If I encrypt a plaintext with different keys for each block, will I have the same security as a one-time pad?

Let's suppose I encrypt an 1MiB plaintext with AES-256 in ECB mode but using different keys for each 16-byte block (I know this is weird but it's just an example). Remembering that a different 256-bit ...
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How to use Pygame to do crib dragging [closed]

I have two files ctext0 and ctext1 that are byte files and they are encoded using the same one time pad, so I tried to write a pygame program to allow me to use crib-dragging to figure out some words ...
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Is AES worse than OTP, if so is there proofs

My train of thought went, OTP is very secure if key is unknown because I am guessing the original message. AES on the other hand tells me I gave it the wrong key, and if I did I can just switch using ...
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Are one time pads still used, perhaps for military or diplomatic purposes?

The ME-600 key generator was developed in the early 1990s for generating truly random one time key streams. That's not exactly World War 1 or 2. I don't know how long it was used, or whether it ...
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Paper based OTP and MAC

Consider the following paper based OTP Plaintext has 11 possible symbols 0-10. $C_i = M_i + K_i\ mod\ 11$. $K_i$ comes from a pre-shared key material which is never reused. How to introduce data ...
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Does authenticating fake Carter Wegman protected OTP messages consume key material at the receiving node?

Assume a message protocol whereby one time pad messages are authenticated with a Carter Wegman type hash on the ciphertext, or some similar construct utilizing a unique authentication key per message. ...
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Security of using key size larger than the message digest size in HMAC, with one time pads

I would like to know the security of using key size that is larger than the message digest (output) of a HMAC in one time pad encryption. One time pads for the message and the key of HMAC are ...
CuriousCrypto's user avatar
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How bad are human-generated random numbers really (One Time Pad)?

This is a pretty open question, so I'm mostly looking for gut reactions from experts more educated than I. Given these assumptions which are easy to verify with a quick Google search: One Time Pads ...
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Is combining hybrid encryption with OTP worthy?

I'm considering a case when after hybrid encryption (AES Key encrypted via RSA) RSA key will be "splited" like in OTP. On the end one side gets encrypted AES key and "half" key RSA,...
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Is it possible to create a pseudo-One Time Pad by using a key smaller than the plaintext?

Let's suppose I want to encrypt a 10GiB file but I don't want to use a One Time Pad, just a 1MiB key taken from /dev/random (in Linux). I know that the key should not be repeated, but is it possible ...
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Question regarding a subset of p=?np

We consider a language that is $\{0,1\}^n$. We consider three variables $A$, $B$ and $K$ part of that language. A and K are generated through true random generator. We consider not two as is ...
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Why is AES better than one-time pad?

From my limited research into this topic, it seems that AES can be brute-forced. One-time pad, on the other hand, cannot. Why then is it better to use AES than it is to use one-time pad? The only ...
Darcy Sutton's user avatar
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Is there a security risk to use AES-CBC as stream cipher?

I am building a chat application where I want to encrypt each character while they are typing. I would require a stream cipher for that. I am planning to use AES-CBC mode with HMAC. Are there any ...
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(In)security of multiplicative blinding / one-time-pad in a commutative ring

As I understand, the one-time pad can be generalized to any finite group. So, for example, if you consider $\mathcal{P} := \mathcal{C} := \mathcal{K} := \{0, 1, ..., 2^{n}-1\}$ for an integer n, and ...
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Security of Reusing a One-Time Pad with Complement Messages with Errors

Let's say I have two binary messages ($m_0$ and $m_1$) of length $n$ which are bitwise complements of each other such that $$m_0 \xleftarrow{r} \{0,1\}^n \text{ and } m_1 = \overline{m_0}$$ If I ...
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Can cryptographically secure randomness be used to implement one time pad?

if I use an one time pad key generated using a cryptographically secure random source like python's secret module , to encrypt a message, will the one time pad scheme be secure? I think the entire ...
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Is this possible?

So I've been working on a project that aims to allow online distribution of one-time-pads securely. I understand that a pad cannot be reused and must be truly random, and that if it is compromised, ...
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Security of using AND instead of XOR operation for an OTP

With One-Time-Pads I have heard that it is preferential to use XOR because the ciphertext reveals no information about what the plaintext may have been (for each 0 ...
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Is it necessary to (length) pad a fixed length one time pad in the presence of a HMAC?

Imagine a protocol where all one time pad messages are of a fixed length. And they're textual only, à la Truths/Tweets. So a short message would be padded with spaces (ASCII 32) up to the protocol's ...
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Proof that the Family of Toeplitz Matrices is XOR-Universal

Definition of XOR-Universal hash functions by Abidin[1]: A class $H$ of hash functions from $M$ to $T$ is XOR-Universal$_2$ ($XU_2$) if there exist at most $|H|/|T|$ hash functions $h$ $\in$ $H$ such ...
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Doing OTP two or more times with a biased TRNG: Will this have the same security as if was done with a non-biased TRNG?

Let's suppose I want to do One-Time-Pad but I only have a biased true random number generator (TRNG). I XOR to the ciphertext block with another with random data got from the TRNG, e repeat the ...
phantomcraft's user avatar
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What is the Work Factor of the one time pad?

Work Factor is defined as the minimum amount of work (can be the length of the key) to determine the secret key of an cryptosystem (HAC, Menezes, Alfred J. et al). And One time pad have unconditional ...
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Compute OTP key if set of plain texts and its set of cipher texts are known

Given a set of plain texts $P \subseteq \{0, 1\}^n$. Assume we know the corresponding set of cipher texts $C \subseteq \{0, 1\}^n$ produced by applying one-time pad with an unknown key $k \in \{0, 1\}^...
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Perfectly secret variable one-time pad

Consider a variable one-time pad, that is, $\mathcal{M}:=\{0,1\}^{\leq \ell}$ is the set of plain text. Now, this scheme is not perfectly secret, since you can take two plain text of different size, ...
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How could unbreakable encryption be used?

I'm part of a team of students from the Vienna University of Economics, which have the task to find application fields for a new technology. The technology itself is provided by an external partner, ...
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Is this a scenario where reuse of a One Time Pad is acceptable?

I require an encryption algorithm that requires two parties with two different keys to be able to decrypt it. I could double AES encrypt, but I am instead considering AES encryption followed by a OTP ...
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Is it possible to decrypt my message if encrypt it twice using different keys each time?

Suppose I want to encrypt $mssg$ using One-Time-Pad, and I want the $mssg$ to be encrypted twice. Once with $k_1$ and second with $k_2$ Is it still possible to detect my $mssg$? lets say: $c_1 = mssg ...
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Where should MAC keys come from in a one time pad situation?

I refer to questions For a one-time pad, which MAC method is information-theoretically secure?, Seeking clarification of OTP & MAC discussion and this page illustrating various MACi. And the ...
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Why do we need to use PRGs to generate random numbers for a one-time-pad? [duplicate]

I'm looking at the following idea for using a symmetric key to encrypt multiple messages (back & forth communication between Alice & Bob). It can be summarized as follows: Both sides agree ...
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What's bad about idea of public-key/one-time-pad hybrid cryptosystem?

As i know, generally nowadays hybrid protocols are more widely used than either symmetric or public key cryptosystems separately. I read that public key system is used to exchange and share secret via ...
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Purpose of modulus in one-time pad?

I have the following question and don't really understand it. I thought OTP offers perfect secrecy, why do we need modulus? Can somebody please help me answer the question? $Z_n$ denotes the ring of ...
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One time pad, Proof for a problem

We know 2 plaintexts of length L and 2 ciphertexts of length L(we don't know which one belongs which), assuming each given ciphertext is generated by encrypting one of the given plaintexts by XOR'ing (...
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cracking a one time pad using key reuse

There is a one time pad which works as follows: given message "hello" and key "asdfg", it produces "hwoqu". It only works with the 26 english letters. The output is (h(7) ...
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One-time pad without zero: proof check

I started learning cryptography and tried to work through this problem: consider one-time pad where $\mathcal{M}=\mathcal{C}=\{0,1\}^n$ and $\mathcal{K}=\{0,1\}^n\setminus 0^n$ (call this scheme $\Pi$)...
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Derivating random numbers from random numbers

If I have a "truly random number" $K$ of $L$ bits (whatever "truly random" means... is it a value from a normal distribution a truly random number, or only uniform distributions ...
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Is OTP still perfectly secure if we limit message and key space

If we have a message space M {0,1,2,3,4,5,6} and likewise keyspace is K = {0,1,2,3,4,5,6} (generator choosen uniform keys k) We define our encryption to be the XOR of their bitwise rep on K and M ...
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Why is mod calculation necessary in a one time pad encryption?

Considering the English alphabets to be encrypted why is the computation of mod 26 necessary after adding the pad to plain text. Is it just that it adds to another level of encryption or is it used so ...
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What is the correct order of operations for one-time pad cipher when using subtraction and mod 10 arithmetic?

What would be the proper order of operations for OTP encryption/decryption when using subtraction and mod 10? E.g. P - K = C or K - P = C Most of the sources I have seen do not cover this topic or I ...
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What is a ciphertext only attack and how OTP is unbreakable using this attack

I was wondering that what actually is cipherText-only attack and how the One Time Pad Encryption cant be broken by this attack?
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One-time-pad Encryption in C

I have been messing around with cryptography (for recreational use), and I created my own one-time-pad encryption script in C. Now, with that being said, I freely admit that I am by no means a ...
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