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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68 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) ...
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When does multiple OTP encryption become insecure if new keys are permuted? ​

I understand that OTP encryption fulfils perfect secrecy, meaning you can't decrypt the encrypted text to it's original plaintext (and know that this plaintext is indeed the original plaintext) unless ...
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Why is this OTP decryption wrong? [on hold]

i have a problem that goes: ...
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Is One Time Pad considered Chosen-Plaintext Attack Secure?

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 ...
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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 ...
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How does bit-wise operation work for encrypting grayscale images?

How does bit-wise operation work for encrypting grayscale images? In my Khan Academy course they encrypt an image with bitwise_and, ...
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Can I securely refill a one time pad over the same connection?

If you have a channel where you are communicating using a one time key, is it possible to receive additional key over that same connection without compromising security? Naively sending it through ...
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Is modern encryption needlessly complicated?

RSA, DES, AES, etc., all use (relatively) complicated mathematics to encrypt some message with some key. For each of these methods, there have been several documented vulnerabilities found over the ...
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Can we use numbers as a pad in the Vernam cipher - why or why not?

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 ...
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What is the fastest way to generate a truly random one-time pad without electrical or any other complicated device?

I want to generate a 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?
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Authentication using a one-time pad

I am building a small embedded system of two nodes that communicate wirelessly. The microcontrollers I'm using are very limited: they only have 256 bytes of RAM. I would like to be able to ...
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861 views

One-time pad XOR question

For a one-time pad to be truly secure, do I need to use XOR? In other words, is a numerical OTP as secure as a XORed one? I'm new to cryptography, so this might not even make sense.
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Using a one-time pad with a block cipher

The one-time pad is often described with a simple XOR cipher. This is nice for showing the theoretical strengths of the one-time pad, but not so great in real-world scenarios where key reuse is a ...
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Hash functions to generate a one-time pad

Maybe this is a newbie question: Stream cypher, will XOR message bits with one-time pad bits. Suppose I have a pseudorandom number generator, like a Mersenne Twister or something similar. I could use ...
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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?
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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 ...
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What is the difference between a Vigenère cipher and a one time pad cipher?

I'm doing a decryption competition at a nearby college. We are allowed one cheat sheet so I'm trying to make one. I realized that the Vigenère cipher was very similar to the one time pad and wanted ...
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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 ...
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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) ...
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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 ...
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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 ...
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Many time pad if cleartext contains arbitrary bytes

I understand the problem of reusing the same key in the one-time pad if the cleartext message only contains characters such as A-Z, a-z and spaces. But what if our cleartext is composed of arbitrary ...
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One-time pad encryption of ASCII characters [duplicate]

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 ...
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Is one-time pad encryption vulnerable when near identical data is sent many times with different OTP?

Let's assume a text file that grows at its very end but is otherwise not edited. We now have 100 transmissions of this, but OTP-encrypted (different OTP each time, of course). The first 50% of the ...
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Is it easier to crack the Vernam Cipher with more than two ciphertexts

I have just started looking into the cracking of the Vernam cipher with two ciphertexts encrypted with the same key by XORing them and then crib dragging and I was wondering if it is made easier if ...
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When Shamir secret sharing used in one time pad scheme

In the following, all operations are defined over a finite field of prime order. Please note that what I'm explaining below is a part of a bigger protocol, however, to keep things simple I just ...
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Using One Time Pad and RSA compared to using only One-time Pad

Here I implemented One Time Pad first for only one time and then I used RSA algorithm to encrypt the message. For RSA algorithm, I pick p = 2143 and q = 3257 value which does not share any common ...
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What are some real world examples where one time pad encryption is used or can be used?

I understood that One-Time Pad (OTP) encryption ensures perfect secrecy. However, I couldn't find any real-world examples where the OTP is used. Also, which are some real-world examples where it won'...
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What algorithms to use for a secure transport protocol on devices with limited computing power

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 ...
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double encryption - One Time Pad

Can the security of the encryption system be improved by using double encryption with two randomly chosen keys? By double encryption I mean using two keys K1 and K2, each 20-bit long, to obtain ...
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Does a stream cipher provide perfect secrecy?

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 ...
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Is the One Time Pad secure in additive Rings?

Let's assume all operations are done on $\mathbb{Z}_p$ where $p$ is a large non-prime number. To mask a value $a$, we do the following: Pick a uniformly random value: $r$, from the ring. Do as ...
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What is the difference between a stream cipher and a one-time-pad?

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 ...
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Is one time pad cipher reuse and random key secure?

The sender and receiver share two different secret keys: s1 and s2 both y bit values. 'x' is a randomly generated y bit value. The reader sends to the tag a challenge y = x ⊕ s1, and the receiver ...
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One-Time Pad Vulnerabilities [duplicate]

Why is it that a one time pad is vulnerable is the key is shorter than the message? I know that if a key is reused across multiple plaintexts, you can XOR two existing ciphertexts to get the pad, but ...
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Simple One time Pad Probability

We have a one time pad where: We have 8 bits. probability that a bit=0 is p. The key is common for all 8 bits. It can have a value of 0 or 1 with equal probability. After applying the XOR operation ...
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Is OTP with homomorphic encryption trivial?

If my key size is as large as the data I'm encoding, is it trivial to devise a theoretically secure homomorphic encryption scheme for integers (or else any finite/infinite group with order) that ...
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Strictly, is length(key) >= length(message) wrong for one time pads?

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 ...
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One Time Pads and “Bit Flip” Attacks

One Time Pads and Vulnerability to "Bit-Flip" Attacks: I've seen it in this group, and apparently there are a (small) number of voices on the 'net opining that those relying on OTP are essentially "...
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Is Poly1305 an information-theoretically secure MAC?

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 ...
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Is there a companion algorithm for OTP to ensure integrity and/or authentication?

One-Time Padding is (theoretically) perfect encryption algorithm. Let's assume that these problems are solved: Fast generation of independent and identically distributed random variables Perfect key ...
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Proof one-time pad is perfectly secret with eavesdropping game definition

I have the following definition of perfect secrecy (please assume that the probabilistic version is not available): If we consider the eavesdropping game given by: $$\begin{array}{|r | r|} \...
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One-time pad encryption - how does the receiving side decrypt the message?

If a message is sent using one-time pad scheme, which generates random bits in order to, for example, XOR them with the message's bits - how does the receiving side generate the exact series of bits ? ...
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Is the Vernam (One Time Pad) cipher useful? [duplicate]

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 ...
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Transferring Encrypted One-time pad over the internet

I was working with one-time pad, and as I understand , for one time pad to be 100% secure a key shouldn't be repeated. So assuming Alice and Bob have to exchange messages over the network secured over ...
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Is a hash more or just equally representative of the first [hashlength] bytes of the hashed one-time pad?

[Clarification edit further down.] To distinguish already existing one-time pad files by their content instead of just their name ... ... is hashing meaningful? Or would the first X bytes (Length ...
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How to be sure to retrieve the good key when brute-forcing a cipher?

Imagine the case of the one-time pad. It is proved to be secure because the key could be everything. We have no guarantee that this key or that key was the one used while encrypting our data. ...
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Generate one-time-pad with pre-shared key and public randomness

I know very little about cryptography, so I apologize if the question does not make sense. Let's say we design a function $F(P, X) \rightarrow K$ that takes in a pre-shared private key $P$ and a ...
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How to compare one time pad security and efficiency with AES?

It seems that the minimal size of Pseudorandom permutation (PRP) output is $128$ bits. In general, I'd like to see if there's any minimal size of the output of pseudorandom function (PRF) as well? for ...
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One Time Pad - does it work for long plain texts?

Reading Dirk Rijmenants's work on One Time Pad and he frequently mentions that it is suited to short plaintexts. I presume this is just because of the practicality of encrypting and decrypting one ...