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.
-2
votes
2answers
68 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
57 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] + ...
0
votes
2answers
75 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
87 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
89 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 ...
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 ...
16
votes
5answers
7k 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 ...
2
votes
2answers
114 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 ...
5
votes
2answers
487 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 ...
2
votes
3answers
80 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 ...
1
vote
1answer
66 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
81 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
719 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
221 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
130 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 ...
6
votes
4answers
922 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 ...
1
vote
2answers
272 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
287 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
322 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 ...
1
vote
3answers
222 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 ...
1
vote
1answer
258 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
215 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 ...
1
vote
3answers
175 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
votes
2answers
253 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 ...
2
votes
4answers
341 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
302 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.
...
1
vote
2answers
247 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
121 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 ...
4
votes
1answer
267 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 ...
1
vote
1answer
492 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
...
2
votes
1answer
340 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 ...
8
votes
3answers
456 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 ...
0
votes
3answers
260 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
226 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 ...
