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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Hash function as secure as one-time pad?

We know that the one-time pad is provably secure as a cipher to encrypt some data. Is there an algorithm which does the same just as a hash function? Can we get a provably secure hash function? Maybe ...
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781 views

One-Time-Pad with key-reuse: Faster way of decrypting?

I know there are already of few questions about this and I'm working with the advices that were given but I still doubt my approach is the fastest, so I'd really appreciate if you helped me find a ...
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37 views

Attackability of one-time MAC when using block mode

Consider an encrypted message m which is encrypted with AES-CBC, so in addition to the message there is an IV supplied initially....
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36 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 ...
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Can an observer deduce a pre-shared key used multiple times on (nearly) random messages?

Imagine you took a standard one-way hashing algorithm (like SHA-256), and you implement it in hardware using simple logic gates. Now, replace each logic gate with an equivalent reversible logic gate (...
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OTP Random Pad Renewal Without Extending Message

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 ...
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49 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 ...
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Are there any historic examples of breaking the one-time pad because of a careless key re-use? i.e simple attack on a multiple-time pad?

It doesn't have be using a truly random key, (it could be the Enigma) but the attack must be based on XORing two parts of ciphertext.
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To prove $r_2$ is a uniformly at random value in $Z_n$, where $r_2=r_1 . m$

$m$ is arbitrary value in $Z_n$, where n is RSA modulo. Then we do: $r_2=r_1 . m (modn)$, where $r_1$ is a random value such that $r_1\in Z^*_n$. ** Question(1): is $r_2$ a uniformly at random ...
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Short one-time pad security

I am somewhat new to Cryptography and I'm struggling with this proof I came across in my Intro to Cryptography course. I understand the proof of security for a one-time pad: Pr[M = m | C = c] = Pr[M = ...
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Forge valid token with misuse of OTP key reuse

I'm new to OTP and received a challenge. Challenge Context: A server uses OTP to encrypt and decrypt authentication tokens. Misuse: The server always uses the same key. Objective: Forge a valid token ...
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1answer
43 views

Authenticated, Quantum-resistant GPG2?

GPG2 does not provide authentication. It still uses SHA-1 by default. It does not seem to get any stronger as time goes by. If one were to pass a randomly-generated symmetric key (from a TRNG) over ...
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Attack on Many Time Pad

I have 7 ciphertexts that have been XORed with the same key. I'm writing a program to figure out what the plaintexts are and possibly maybe recover the key. I have managed to convert the HEX ...
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Are there any known problems performing a One-time pad with 2 keys stored separately - AKA 2 part Symmetric key exchange over TLS

If this is something that already has a name, please tell me to look at that, but I have not been able to find one yet. I am considering this process for storing some data securely. I want to ...
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1answer
87 views

Can a message and one time pad each encrypted with separate ciphers be weaker than the stronger of either cipher?

Assume you have: A truly random one time pad, $P$ A plain text message, $M$ Two symmetric ciphers, $C_S$ and $C_W$, where $C_S$ is always more secure than $C_W$ Assume the keys have already been ...
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54 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, ...
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91 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 ...
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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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1answer
56 views

The security of adding random noise many time pad

In may application, I have a series of real number $\{v_1, v_2, \ldots, v_N\}, v_i\in\mathbb{R}$. To protect them, I add a random noise $r\in\mathbb{R}$ to each themselves like one-time-pad encryption ...
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Modifying the One-Time Pad so that one key can be used two times

I'm currently working on a modified one time pad and I'm trying to use the encryption scheme such that the key will be used twice. I have written a small pseudo code but I'm stuck. Here is my attempt: ...
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Which is more secure, AES CTR or OTP with generate key?

My idea of the OTP is to generate from 50 letters (5 words, each 10 letters) a new pad of 2000 random letters, then attach user email to the pad end (to make it unique). The keywords and the pad will ...
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1answer
105 views

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 ...