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.

Filter by
Sorted by
Tagged with
1
vote
3answers
329 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 ...
1
vote
1answer
282 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 ...
0
votes
1answer
187 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 ...
4
votes
2answers
307 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 ...
1
vote
1answer
333 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? ...
11
votes
3answers
2k 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 ...
1
vote
1answer
104 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 ...
5
votes
2answers
303 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 ...
18
votes
12answers
16k 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 all ...
1
vote
1answer
228 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) ...
10
votes
7answers
975 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 ...
-2
votes
1answer
944 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 ...
1
vote
2answers
174 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 ...
-1
votes
1answer
1k 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 ...
0
votes
2answers
262 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 ...
0
votes
1answer
772 views

Using the OTP and RSA compared to only using the OTP itself

To use the OTP with RSA, I implemented the one-time pad first for only one time, and then I used the RSA algorithm to encrypt the message. For the RSA algorithm, I pick $p$ = 2143 and $q$ = 3257, ...
5
votes
3answers
786 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 ...
-2
votes
1answer
96 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,...
1
vote
0answers
77 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 ...
5
votes
1answer
178 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 connection without compromising security? Naively sending it through ...
2
votes
1answer
152 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 ...
4
votes
1answer
225 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 ...
3
votes
1answer
107 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?
-1
votes
1answer
64 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 ...
2
votes
4answers
2k 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 ...
3
votes
6answers
767 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 ...
4
votes
1answer
1k 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, ...
4
votes
4answers
3k views

One-time-pad encryption

As we know, intercepted ciphertext created by a one-time pad only reveals the length of the message. That is the only information the attacker can get since this ciphertext is unbreakable without the ...
3
votes
1answer
125 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},...
2
votes
1answer
1k 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.
0
votes
1answer
270 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?
2
votes
1answer
178 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 ...
3
votes
2answers
979 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 ...
1
vote
1answer
173 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 ...
0
votes
1answer
66 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 ...
1
vote
1answer
4k 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), ...
3
votes
1answer
238 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 $\mathbb{Z}_N$...
2
votes
1answer
97 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 $b$ ...
1
vote
1answer
491 views

Is a stream cipher similar to One-Time Pad using hash secure?

I've read some Q&A about combining OTP with hash on this site, but I still wonder why some answers said that using hash for OTP key is not strong enough to resist brute force attack? Assuming ...
11
votes
2answers
2k views

Why would Carter-Wegman-style message authentication not be broken by P = NP?

Researching about the implications of P = NP to cryptography I found someone say that the only cryptography left standing would be the one time pad and Carter-Wegman-Style message authentication. ...
1
vote
1answer
314 views

How can I determine key length for message encrypted by many-time-pad?

For message $ m $ and key $ k $ I get encrypted message $ c $ ($ m \oplus k = c $) where $ length(k) < length(m) $. Additionally I know that message $ m $ is English text. Instead of using pure ...
2
votes
2answers
286 views

How can I create pre-determined encrypted results?

I want my encryption results to be the lyrics to Star Spangled Banner. The original text I'm encrypting would be, for instance, the menu to a local pizza place. I know what I want my passphrase to be. ...
1
vote
0answers
51 views

Truly Random Values [duplicate]

I am trying to build a one-time pad encryption software and I am thinking about simply using /dev/random to generate keys. My question is: Is it ...
2
votes
2answers
1k views

What are the correct order of operations for One Time Pad Cipher?

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 ...
-2
votes
2answers
2k views

Is the one-time pad secure?

I have read about one-time pads (OTP) on Wikipedia. Is this secure? Can I actually use modular addition as ecryption like it said in Wikipedia? And the plaintext is as long as the OTP, so when I send ...
-2
votes
1answer
228 views

Randomness of a Key in a One Time Pad

The keys used in an One Time Pad are required to be randomly generated from a keyspace $\mathcal{K}$, we require 256 bit random keys, i.e. $\mathcal{K}=\{0,1\}^{256}.$ Suppose we randomly select an ...
1
vote
1answer
237 views

Does sending the same message with 2 different keys in OTP leak information?

Suppose a common message ($M$) is XOR'ed with two different keys $K_1,K_2$ producing two ciphertexts $C_1,C_2$. Thus, $$M \oplus K_1 = C_1\\ M \oplus K_2 = C_2$$ On observing $C_1$ and $C_2$, an ...
8
votes
4answers
3k views

If I am about to generate one-time pad, where should I generate my pads from?

If I want to generate a few one-time pads, is it OK to just read required number of bytes from /dev/urandom without weakening information-theoretical security?
0
votes
1answer
299 views

CPA on theoretical OTP with CBC mode

Body of question Note: this is THEORETICAL exercise. I understand OTP and CBC does not get along. I have to find a CPA on CBC enc-mode using OTP as the encryption algorithm, s.t a new key is ...
0
votes
1answer
376 views

One-time pad using RSA and Diffie-Hellman functions

Suppose that Alice and Bob use an encryption algorithm based on a one-way function $F$ (Eve knows it), and $r$, a secret key shared between Alice and Bob (Eve doesn't know it). Key is computed as: $K =...

1 2 3
4
5
8