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.
4
votes
7answers
253 views
Algorithm: How to use x and y mouse movement co-ordinates to generate random data?
Background:
I'm making a program for fun as a learning exercise. I want to generate some actual random key material (not pseudorandom) from a JavaScript program. For my program is just for ...
2
votes
2answers
112 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
2answers
71 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
votes
0answers
66 views
One time Pad Adversary
I like know Why $Pr[\mathsf{PRIV_{EAV}}(\Pi,A,n)=1] = 1/2$, when $\Pi$ is a One Time Pad. I trying:
$$Pr[\mathsf{PRIV_{EAV}}(\Pi,A,n)=1] = Pr[b'=0|b=0]Pr[b=0] + ...
1
vote
2answers
101 views
random number generator 10-side dice alternative
A lot of sites like this one Here, refer to 10-side dice to generate random number for otp. I was thinking about new ways to generate random numbers,letters and passwords. here what I got.
to ...
2
votes
2answers
97 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 ...
0
votes
1answer
100 views
decryption many time pad
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 ...
2
votes
2answers
126 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
85 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 ...
2
votes
1answer
96 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
vote
0answers
84 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 ...
3
votes
2answers
769 views
Many time pad attack
I've already sent my correct solution to a programming question on an online class:
Let us see what goes wrong when a stream cipher key is used more than once. Below are eleven hex-encoded ...
0
votes
4answers
228 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
votes
1answer
134 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.
1) I ...
2
votes
4answers
293 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 ...
0
votes
4answers
345 views
“Padless” One-time-Pad encryption
I have just read about the perfect security of an OTP encryption and what came to my mind was that what if the Pad used for encryption/decryption did not have to be transported separately from the ...
-2
votes
4answers
284 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 ...
2
votes
2answers
238 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 ...
2
votes
2answers
303 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 ...
1
vote
3answers
188 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 ?
1
vote
1answer
268 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 ...
1
vote
2answers
292 views
Simply put, what does perfect secrecy means?
I would like to ask for a clear (but maybe not so deep) explanation of what the term "perfect secrecy" means.
As far as I have researched and understood, it has to do with probabilities of assuming ...
2
votes
4answers
364 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 ...
3
votes
5answers
306 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.
...
5
votes
2answers
523 views
HRNG for One Time Pad
I have just advanced to the last grade of high school (in Denmark). In this year, we all get to do one big project, where we can build/invent/create whatever we want to "solve a problem". As I study ...
1
vote
2answers
256 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 ...
2
votes
1answer
126 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 ...
1
vote
1answer
532 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
...
4
votes
1answer
273 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
353 views
What is the correct way to generate cryptographically-secure pseudorandom numbers in C?
I am learning about crypto, purely for my own interest. As part of that I am implementing a simple 'one time pad' toolset in C.
Naturally I need to generate random numbers to create the pad, and they ...
9
votes
3answers
472 views
Can I use a one time pad key twice with random plaintext?
I understand the basics of OTP: $|\text{key space}| = |\text{plaintext space}|$ implies perfect security, key reuse destroys this.
Cryptanalysis on the $N$-Time Pad for $N > 1$ involves finding ...
8
votes
2answers
6k views
How does one attack a two-time pad (i.e. one time pad with key reuse)?
My question might appear the same as the question Taking advantage of one-time pad key reuse?, but actually I did read all the answers and none of them helped me with the details I need.
I am new to ...
0
votes
3answers
264 views
Can PBKDF2 be used to create an OTP to encrypt random plaintext?
I want to encrypt a truly random plaintext (a key file) based on a user password. I'll use PBKDF2-HMAC-SHA256 to generate an encryption key from the password, but I'm wondering if I even need to both ...
2
votes
2answers
229 views
Why not use an algorithm's code rather than data itself for one time pads?
Instead of using actual data for one time pads, what would be different if the code for an algorithm was exchanged so that to acquire the pad one would execute the algorithm and use its output? Why ...
6
votes
4answers
965 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 ...
16
votes
5answers
8k views
Taking advantage of one-time pad key reuse?
Suppose Alice wants to send encryptions (under a one-time pad) of $m_1$ and $m_2$ to Bob over a public channel. Alice and Bob have a shared key $k$; however, both messages are the same length as the ...
