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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0
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4answers
614 views

Is the One Time Pad (OTP) considered a cryptographic hash function?

As the title states, would the One Time Pad (OTP) be considered a cryptographic hash function?
4
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1answer
169 views

Would a symmetric cipher with a keylength a big as the data length be information theoretically secure?

One-Time-Pad is information theoretically secure as long as the random number stream is evenly long or longer than the data stream it encrypts, for a "decyphered" message could have been any message ...
0
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1answer
211 views

Does a playlist of songs or movies mixed together contain enough random enough for OTP key material?

Ok hypothetical scenario. Lets say I want to generate a lot of key material quickly for a one-time pad. This key material will be divided up and used for many different messages in the future. I ...
2
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1answer
128 views

Why does a one-time-pad key have to be at least as long as a message? [closed]

I am studying one time pad and find it hard to understand. What happens if the key is one bit or 100 bits shorter than the message?
3
votes
1answer
125 views

One-time pad mistake in the transmission?

I have a question which arised by analyzing the one-time pad cipher. I encrypt a binary sequence $a_1,a_2,..,a_N$ using a one-time pad with key sequence $k_1,k_2,k_3,...$, so I send $a_1+k_1, ...
2
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0answers
244 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 ...
2
votes
4answers
915 views

One time pad key exchange

If two parties want to communicate with securely using OTP , how is the key ( that is lengthy as plain text) shared with other party for decryption ?
2
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1answer
353 views

Diffie-Hellman: Does the size of the prime modulus depend on the potential size of the secret?

I'm writing my own cryptosystem that uses One Time Pad and Diffie-Hellman to generate keys for the OTP. I am using Rails on the server side and Javascript for the client side. Please don't tell me ...
1
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4answers
839 views

Would this simple encrypted chat program be feasible using One Time Pads?

Lets say I want to build a simple chat program that has encryption that is impossible to crack for anyone, even a theoretical government with a massive super computer. Ok here's my idea. You'll need ...
3
votes
1answer
312 views

What is the name of this kind of protocol

There is a communication protocol that I believe creates the equivalent of a one time pad, with the downside that the secret message must be transferred multiple times. The protocol is so simple that ...
5
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1answer
309 views

Can two people with different one time pads securely exchange a message like this?

Alice has a message, generates a one time pad, encrypts her message and sends it to Bob. Bob generates his own one time pad, encrypts the message again, and sends it back to Alice. Alice then decrypts ...
3
votes
2answers
261 views

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 ...
2
votes
1answer
225 views

Having 4096 bit keys and short (< 256 byte) messages, can I simply use the key as OTP?

Assumptions: Alice and Bob use (cryptographically secure, hardware-rng generated) 4096 bit keys. Each message is encrypted using a new key; meaning: once a key is used, it's destroyed. Alice and Bob ...
2
votes
2answers
465 views

Is OTP useful in modern electronic communication?

I have seen from time to time questions about various OTP schemes and "OTP" (i.e. stream cipher) schemes. The most common OTP troubles appear to be: How to extend size of previously generated key or ...
3
votes
2answers
241 views

Can you really insert the text you want in one-time pad?

The Wikipedia article "One-time pad ~ Authentication" says : For example, an attacker who knows that the message contains "meet jane and me tomorrow at three thirty pm" at a particular point can ...
-2
votes
1answer
451 views

Is my one time pad cipher secure?

This is a program that I made for encrypting text files. It uses a one time pad cipher to encrypt the files, but I do not know if there is any holes in my program that could be a vulnerability. Is my ...
2
votes
3answers
289 views

One-Time Pad Distribution of Keys Between Two Parties

Consider the One-Time Pad (OTP). Suppose two parties, A and B, generate a completely random secret key in a real-life meeting, and they keep this secret. Now A wants to send some message to B using ...
2
votes
2answers
186 views

Privately Sum Values without Dealers, MPC

Suppose $n$ actors each hold a plaintext $p_i$. We wish to find $\sum p_i$, without leaking any information about individual $p_i$. Any actor (or any link in the network) could be controlled by an ...
3
votes
3answers
724 views

Implementing a one-time pad without binary?

This is a program that I found which takes a purely alphabetical message, converts the letters to their ASCII values and combines them with the ASCII values of an alphabetical key (wrapping around ...
3
votes
4answers
977 views

random number generator 10-side dice alternative

A lot of sites (e.g. Dirk Rijmenants') refer to 10-side dice to generate random number for one-time-pad. I was thinking about new ways to generate random numbers, letters and passwords. here what I ...
2
votes
1answer
157 views

Can OTP still be broken if there are several messages being sent with only a slight variation in a password?

If an attacker were able to get a hold of 2 encrypted messages that were both encrypted in a one time pad with a password that were each similar but had one change in the first character, could it ...
3
votes
2answers
200 views

Is this OTP scheme safe?

I have a message $m_1$ and I want to encrypt it by XORing it with two keys $k_1$ and $k_2$: $$c_1 = m_1 \oplus k_1 \oplus k_2$$ So far so good. Now I was wondering if I could create a "fake" result ...
2
votes
1answer
175 views

Isn't the structure of a potential plaintext of a ciphertext generated by a one-time pad dispositive, cryptanalysis-wise?

That is, if I generate every possible result, and analyze the structure against, for example, a dictionary, won't that identify which of the solutions in the domain is most likely the correct one? I ...
-1
votes
2answers
404 views

Perfect Secrecy, two Definitions

I'm reading the proof of the implication "Def 2.1 $\Rightarrow$ Def 2.4" in these slides about Adversarial Indistinguishability and Perfectly-Secret Encryption. I have a doubt in the slide 10. Here it ...
2
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2answers
522 views

encrypt message with one digest 0-9 instead of 01-26

How much will the security of one-time pad decrease if I use one digit from 0-9 instead of 1-26? for example plaintext = "blue" and ...
1
vote
1answer
3k views

decryption many time pad [duplicate]

I have eleven ciphertexts that were encrypted with the same key (which I don't know). I want to decrypt the last ciphertext. I read similar question like Many time pad attack but I can't solve my ...
3
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2answers
842 views

one-time pad key related attack [duplicate]

In one-time pads we always say do not use same key twice to encrypt ASCII messages, but if we use a random key to XOR a random ...
2
votes
3answers
170 views

How comparable is OFB to a one-time pad?

This is a rather trivial question, I just want to see if I get the concept right. In OFB you generate a pseudorandom stream based on some nonce, and you XOR that with the message to get the ...
3
votes
0answers
267 views

One-time pad and perfect secrecy properties

I have a homework problem: Explain how to find $m_{0}$ and $c$ such that $P[c=c': k \leftarrow K, c' \leftarrow E(k, m_{0})] > 0$ where P is probability and k is chosen uniformly. I do not know ...
11
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4answers
4k views

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 ...
3
votes
4answers
660 views

Randomized algorithms and the one time pad

The way I understand it, an algorithm is said to be randomized if it uses randomness as part of its logic (quoting Wikipedia). Now, in the case of encryption algorithms, I assume this means that for ...
3
votes
1answer
1k views

One-time pad and zero key

I'm doing some exercises before my exam, and I am stuck with task number 4 in this file: http://www.cs.umd.edu/~jkatz/crypto/f10/hw1.pdf Could you help me with this task? When using the one-time ...
2
votes
2answers
732 views

Avalanche noise RNG for one-time pad use

I came across this little HRNG widget and was really intrigued as I have been looking for a decent but afordable source for truly random bits to use in a one-time pad. The question is, would a HRNG ...
4
votes
2answers
2k views

Perfect security definitions

In my notes, there are 2 definitions of perfect security: "For $M \in \{0,1\}^m$, define the distribution $D_M$ on strings as follows: to choose a random member of $D_M$, choose a random $K \in ...
3
votes
4answers
1k views

Which is more secure using a CSPRNG for a One-time pad, or AES?

In reading about the One-time pad it appears to need truly random key for the pad. Since true random values are not practical to generate this presents a problem (thus making One-time pad less ...
6
votes
5answers
659 views

Are picture files “random enough” to be usable as a one-time pad?

Say you have a picture with 1 megapixels taken at random and with $2^{24}$ possible colours per pixel (RGB-24). That image would be unique and the possible combinations $(2^{24})^{10^6}$ immense. ...
2
votes
2answers
2k views

Difference in one time key and one time pad and many time key

These terms are confusing me. One time pad is when you use one key for one message. That is what One time key is. Secondly, what is the connection of many time key, can i use one time pad many ...
4
votes
1answer
464 views

How secure is my OTP program?

I'm writing an One-Time Pad encryption program, because I got really interested in the idea of " encryption which has been proven to be impossible to crack if used correctly". I'm writing the program ...
2
votes
1answer
2k views

Deciphering a key from XOR encrypted cypher using boolean logic

Assume there's an unencrypted message A, and an encrypted message B. You know that message B was encrypted using a simple XOR method of A with a private key K, resulting in message B. Thus, B = A ⊕ K ...