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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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314 views

Given a list of ciphertexts, how to identify the ones that used the same key for encryption

I'll start off by saying I am not looking for solutions here, just suggestions on how to proceed. I am given a short list of ciphertexts (20something) and I know that one of the ciphertexts has been ...
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2answers
393 views

Can I generate OTP secrets by using a hash?

Since I learned about one time pads in last security lecture, I'm quite fascinated how easy the concept is, but how it still is absolutely safe. Learning from implementing a multi time pad attack, ...
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3answers
627 views

Why in one time pad must the key distribution to be truly random

One time pad required a truly random key. Why canwt it be a psudo-random key? For example, if the key distribution is that for each bit the probability to get 1 is 0.6 and the probability to get 0 is ...
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1answer
118 views

is the perfect secrecy of one time pad dependent on the xor randomness preserving property?

Is the perfect secrecy of the one time pad dependent upon the xor "randomness preserving" property (xoring a uniformly random string with any string yields a uniformly random string)? I have seen ...
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4answers
215 views

Including the next random One Time Pad as part of the encoded message?

I've tried to do something very simple here, which is to encrypt a message with a one-time-pad (OTP) and include the next OTP as part of that same encrypted message. i.e. The first message consists of ...
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4answers
230 views

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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2answers
269 views

Decrypting two XORed compressed messages?

If through a previous attack, cipher misuse or two time pad etc. I receive $c=m_1 \oplus m_2$. Where $m_1$ and $m_2$ are compressed messages, for instance GZIPped English text documents. Can we ...
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1answer
106 views

Stuck on finding M2 knowing M1 in One Time Pad

Lets say I have a plaintext M1 and a plaintext M2, I know both the ciphers C1 and C2 from these M1 and M2. But from M1 I also know a piece of M1 or maybe even the whole text. And I also know C1 XOR C2 ...
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1answer
284 views

Is a one-time pad secure if the encryption method is not?

(The following situation is hypothetical.) I need to communicate something securely and I have decided to use one-time pads. I am going to be using human genes as the source of the OTP data (this is ...
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3answers
196 views

Generating OTP using Digital Dead Drop

I've had a thought and I'm wondering if this would be a useful way to devise and distribute a one-time pad. It relies on a digital dead drop and a hash function. The digital dead drop could take a ...
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1answer
222 views

One way communication with forward secrecy?

Is it possible to achieve forward secrecy using a one way communication channel with pre-shared secret? I have a setup where I need to send some information across a unsafe channel between server A ...
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3answers
202 views

What are the vulnerabilities of this OTP-like system?

I've read that a OTP is only perfectly secure if the key is perfectly random, and the pad is never reused. If you encrypt documents using two keys, where one is random but stays constant for some ...
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1answer
215 views

Is creating an OTP of a key to some data a secure secret sharing scheme?

Suppose I have some data that has been encrypted with a known, secure algorithm and a key k. I want to distribute "pieces" of the key to n of my colleagues, and only be able to access the data when ...
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1answer
125 views

Multi-Embedded Xor for Perfect OTP

I am looking for a perfect OTP design, so let's see if this design is good. There are 2 issues when it comes to a good OTP system, the key and the plaintext, we will use XOR as cypher: If the ...
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2answers
214 views

Viability of using One-Time-Pad + HMAC in low-volume IoT communications

In the Internet-of-Things world there are certain applications that produce very low volume communications. For example reading a water meter once every hour comes to mind. If the reading could be ...
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1answer
206 views

How to attack a two time pad if the plain text is randomized?

As an extension to this quesiton, or this one how would you go about attacking a re used pad if the plaintext was randomized before being encrypted? ...
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3answers
671 views

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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1answer
78 views

Perfect Deniability of a MAC Protocol

I proposed an idea of Perfect Deniability of a MAC I tried to come up with a protocol that satisfies those security requirements as well as the normal security requirements of a MAC One-Time MAC ...
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2answers
193 views

Perfect Deniability of a MAC

Overview One feature that is often underlooked of the One-Time Pad is its perfect deniability. i.e. If Alice sends a message to Bob that is seen by Eve then if Eve later goes to Alice with the ...
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12answers
12k views

Are one-time pads crackable in theory?

I've been taught that one-time pads are the only perfect encryption, since the only way to recover the message is by knowing the key. For example, for a target bitstring of 100 bits, I cannot scan ...
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1answer
149 views

Attacks on Biased OTP

I know that a perfectly random unbiased and not reused OTP cipher is perfect. An OTP under cryptanalysis has a very strong bias (up to 30 % of symbols are represented by 5 out of 255 possible symbols) ...
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6answers
595 views

Does humanly verifiable one time pad authentication exist?

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 ...
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1answer
469 views

How to Encrypt WAV file using One-time Pad Algorithm

I am confused about what parameters that I must encrypt on a WAV file. If the file is text, it's only required to convert the character to ASCII code; if picture, just encrypt the pixel. What is ...
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2answers
141 views

Hiding the metadata of a one time pad message by encrypting the next key

here is an idea that I feel has some big flaw I can't put my finger on. The scenario is: Alice will go overseas for 5 days and will hopefully retrieve some information and send it back to Bob. She ...
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1answer
635 views

How to decrypt a code with a given OTP key practically [closed]

For practicing purposes I obtained some cipher and an OTP key. Now my task is to decrypt the cipher using this key. Both files are .bin files and when I open them with TextEdit there are a huge ...
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2answers
185 views

How could consumer level OTP + QKD over the internet ever be practical?

Please note, I am in no way questioning the future usefulness of quantum key distribution (QKD) in certain applications. I have no doubt it will prove useful for large banks, and in certain military ...
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0answers
320 views

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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3answers
472 views

One Time Pad Alphabet Size

I am building a simple one time pad system using a low-power microcontroller to XOR a stored key with an input string, and vice versa. Due to several internal factors, it's very preferable for the ...
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1answer
92 views

Is this cryptographically secure?

If I securely (manually) give/put two computer (Alice and Bob) a secret key, they can securely communicate to each other (?) Alice encrypt a message (maxlength = secret key length) and send it to Bob,...
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0answers
73 views

Decrypt Messages With Reused Pad [duplicate]

I have 2 messages which have been encrypted using the same pad. I know that if i xor these 2 messages together the key falls out. I am confused in how to figure out what the 2 messages are from the ...
4
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1answer
113 views

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 coonection without compromising security? Naively sending it through ...
3
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1answer
105 views

Extracting the pad in case of one-time-pad reuse without XORing

I had to decrypt two book passages from different books which had both been encrypted using the same one-time-pad, and automate the process at that. I've found a few explanations of how this could be ...
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1answer
150 views

Is there a name for encrypting a decimal number using a one time pad?

I asked a question somewhere else on stack exchange and had to put something like "using the numerical one time pad the user can create their encrypted message by hand". Is there a better way of ...
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1answer
100 views

How to detect if n long messages have encrypted with the same one-time pad?

I have a slight idea on what the attack would be. But my question is: how would one detect if n long messages (n>5) have been encrypted with the same one time pad, K?
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1answer
57 views

What to do with this specific scenario of a key reuse [duplicate]

I am brand new to the world of cryptogrophy. I am trying to decrypt a many-time-pad. I understand the methodology of using the XOR to get the messages. C1 XOR C2 = M1 XOR M2 Now my question lies in ...
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0answers
34 views

Cryptanalysis of vernam cipher with four ciphertexts encrypted with same key [duplicate]

I am working on a class assignment which is to demonstrate that vernam cipher (one time pad) is insecure when the keys are repeated. So I have four cipher texts of length 1024 bits each encrypted ...
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4answers
813 views

Would using a one-time pad multiple times with some conditions be safe?

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 ...
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6answers
542 views

Does one time pad randomness help brute force attacks?

I understand that attempting to brute force the decryption of a message coded with a one time pad results in generating every possible message. The Wikipedia example is that decoding "EQNVZ" with key ...
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1answer
638 views

Why is pseudorandom OTP (P-OTP) IND-CPA insecure

My lecture notes state that P-OTP is IND-COA but not IND-CPA insecure. I understand IND-COA secure, assuming PRG is secure, as that is the whole point of a OTP, but why is it IND-CPA insecure? Surely, ...
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4answers
2k views

One time pad encryption

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 ...
3
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1answer
103 views

Split encryption into two steps

Are there two step encryption systems that - given the same plain text - support choosing two keys ($k_{A_1}, k_{A_2}$) for a first encryption so, that you can calculate another pair of keys ($k_{B_1},...
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1answer
215 views

Non malleable Encryption scheme

I know that one time pad is malleable. Can you give me an example of an encryption scheme which is non-malleable?
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1answer
142 views

Seeking clarification of OTP & MAC discussion

I refer to the question for-a-one-time-pad-which-mac-method-is-information-theoretically-secure, and specifically the exchange between lightspeeder & kasperd. I've found the discussion a little ...
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2answers
861 views

Vigenère cipher with sha512 and a little foresight turns to one-time pad. How safe can be?

I'm doing some exercises and of course I have read about the weaknesses of Vigenère cipher because it repeats the key. But what if I use a different hash every time? The hash of the "key + an ...
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1answer
150 views

What if an attacker knows 1 bit of a OTP ciphertext

I want to know the answer for the question above, given that we encrypt a message that ends with a "0" and the encryption key is concatenated with a "0" to, in that case that case the cyphertext ...
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1answer
51 views

Data switching on one time pad and Data leakage

Assume all the values and operations defined over $\mathbb{F}_p$. For the sake of simplicity assume all the values are non-zero. Let $(-r)$ denote additive inverse of value $r$. We have one fixed ...
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1answer
2k views

Clarification of Proof: Proving perfect secrecy for One Time Pads

I came across a version of a proof that One Time Pads have perfect secrecy and have a few questions with this version of the proof. The proof is attributed to Dan Boneh (the proof starts on slide 10), ...
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1answer
149 views

Cryptanalysis of this one-time pad

My question is related to this: Security of one-time-pad without $\bmod $ operation? but the way we mask values is different here. We consider a finite field, $\mathbb{F}_p$, and a ring $\mathbb{Z}_N$...
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1answer
83 views

Security of one-time-pad without $\bmod $ operation?

Assume $r_1,r_2$ are used only once, and picked uniformly at random (each time we want to mask a value) from finite field $\mathbb{F}_p$, where $p$ is a large prime number. Assume $r_i\neq0$ and $b$ ...
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0answers
28 views

XOF/derivation as OTP [duplicate]

Probably a stupid question but I haven't seen it asked before... What would be wrong with expanding a key to the length of a given plaintext (using Shake or scrypt) and using that as a OTP on the ...