# All Questions

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### Do we have anyway of knowing if avoiding self-permutation in RC4 makes it any stronger?

OK, so lots of questions get asked about RC4 but I want to make mine specific and hopefully answerable. RC4 Design as I'm sure anyone reading this knows, uses self permutation in stage 1 of the KSA. ...
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### Construct IND-CPA secure encryption scheme by combining two given schemes

I have two encryption schemes $\Pi_0, \Pi_1$, at least one of them is IND-CPA secure but I don't know which one. The task is to construct a scheme $\Pi$ that is guaranteed to be CPA secure and to ...
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### What can I do to improve my encyption method [closed]

I'm new to cryptography and I want to learn more. For me, the best way to learn about something that I have no experience with is to experiment and I've coded a very basic approach to a simple ...
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### Is it secure to use hexadecimal data for IV instead of raw binary?

Is it safe and secure to use a function like bin2hex (which converts binary data to hexadecimal) on the binary output of functions like ...
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### Should I be concerned about padding oracle attacks if the lifespan of my key is ~1 minute?

I'm using 4096-bit RSA to encrypt a 256-bit AES key generated client-side. The RSA ciphertext is then sent to the server, and the server decrypts the RSA ciphertext to acquire the AES key. ...
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### Doubts about Authenticated Data Structures logic

I am studying the theory of authenticated data structure, like Merkle Tree and I have a doubt: why use them? I explain better: why to be sure, for example, that a cloud provider didn't modify my files ...
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### What is the difference between MACTripleDES and TripleDES?

I was asked to encrypt/decrypt a string using MACTripleDES. Is there any difference between MACTripleDES and TripleDES? If, where exactly is the difference between both?
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### 2 Part Encryption

Can anyone tell me if an encryption / decryption scheme like the following exists? Encrypted1 = SomeCryptoFunction(Data, Key1) ...
2k views

### Where can I get information on how to implement AES?

I want to write AES from scratch without using the built in libraries of java. I know there are hundreds of AES programs (and websites) out there but I can't seem to find a site that gives me the ...
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### Protocol to identify zone of potential agreement without revealing reservation prices and having to trust third parties?

A wants to buy a company from B. Before A and B enter negotiations, they want to make sure that there actually is a zone of potential agreement. Obviously, they don't want to communicate their ...
84 views

### Adding parameters to sponge's capacity

Is it safe to XOR parameters like domain, length of the message or block counter into sponge's capacity or that gives attacker control over capacity? For example NORX XORs domain into capacity. Does ...
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### Simple RSA Key Generation example [duplicate]

I have two prime numbers: p = 37 q = 41 And I need to find whether any of these prime numbers, 5, 7 or 11, can be used as a valid encryption key e? My working ...
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### how to change math.random() implemented in javascript to securerandom [closed]

In Javscript code in one of our application,I am trying to change Math.random to secure random.I am not sure ,how to change.can anybody help?
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### Finding collisions for the DES F-function

It's known that for a given subkey, the F-function of the DES is not injective (see Is the DES F-function injective for a given subkey?). I am interested in efficiently finding collisions for this ...
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### How do you construct a practical full-domain hash function?

I am looking for practical constructions for Full Domain Hash. I have read Random Oracles are Practical by M. Bellare and P. Rogaway, the construction suggested on page 8, under "Uniformity: a ...
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Considering the following encryption scheme where RSA is used to encrypt a plaintext m and then we choose a random r and compute: $$A = r + m^e \bmod N$$ and $$B = r^e \bmod N$$ So the ciphertext is ...
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### Question about lower bound and upper bound key collision

I'm reading this article and I have a doubt in the page 7. First I going to describe the required definitions and next I formulate my question. Let be F(n)=\{f_k: \{0,1\}^n\rightarrow \{0,1\}^n| k\...
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### Uniformly distributed secure floating point numbers in [0,1)

Is there any way to generate cryptographically secure uniformly distributed floating point numbers in the interval [0,1)? For example, in Javascript, there is ...
98 views

### Proof that perfect privacy implies that the number of keys is at least the number of messages

I was reading a proof to the statement: Perfect privacy implies that $|K| = |M|$ where I am pretty sure that $K$ is the set of keys and $M$ is the set of messages. The proof is the following, ...
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### Which crytographic standard were RC5, CAST5 and Blowfish based on? [closed]

Which crytographic standard were RC5, CAST5 and Blowfish based on? A. AES B. RC2 C. 3DES D. DES
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### Known plaintext, ciphertext, encryption method (AES CBC) and IV (static) [duplicate]

I know the plaintext, the ciphertext, the encryption method (AES CBC) and the IV -- which is static. While not able to perform a chosen plaintext attack per se, I can obtain many known plaintext/...
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### NIST tests for AES [closed]

How to do the benchmarking of a self implementation of AES algorithm using NIST test suites? I am unable to find enough material on the internet regarding this.
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### Finding differentials and space complexity

Most of article about differential cryptanalysis present the generic method, the way to find sub keys. But I can't find a clear explanation about how to find the differentials used in examples. In ...
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### Convert messages to elliptic curve points [duplicate]

Let $E$ be an elliptic curve; $\alpha,\beta$ two points of $E$; and $a$ a private key such that $\beta=a\cdot\alpha$. We choose random integer $k$ and plain text $x\in E$. Encryption and decryption ...
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### AES Key Length vs Block Length

This answer points out that certain key and block lengths were a requirement for the AES submissions: The candidate algorithm shall be capable of supporting key-block combinations with sizes of ...
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### Is it feasible to build an index of prime factors?

Would it be possible to break an RSA key, in for example 1 week of time, if the cracker have already spent X number of years building an index of primes by performing every permutation of existing ...
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### Multiple levels of encryption

Is it feasible to have data encrypted at different levels of hierarchy I'd like to encrypt an xml database (such as used in www.keepass.info) whereby two or more keys can exist. For example: Key #1 ...
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### Is secure lattice based cryptography in future?

Lattice cryptography is a post quantum cryptography that work on two NP-hard problem in below: Find shortest nonzero vector from origin and Find minimum distance of a arbitrary point out of lattice ...
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### Finding Private Key $d$ using RSA [duplicate]

I'm a RSA n00b when it comes to the mathematics for RSA. After spending some time reading, watching lectures, etc. I pretty much have everything down, except for how to figure out the equation for ...
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### Winternitz Signature in standard model

I am studying the Winternitz signature and I describe its algorithms in the next W-OTS Key Generation. Select the parameter $w\geq 2$ that is the bit size of the partitions of the message to be ...
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### What does “Worst-case hardness” mean in lattice-based cryptography?

In the wiki page of Lattice-based Cryptography the "Worst-case hardness" is defined as below: Worst-case hardness of lattice problems means that breaking the cryptographic construction (even with ...
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### Proof of RSA security dependent on public key exponent

I am writing a (high-school) paper on the public key exponent's (in textbook RSA - no padding is discussed!) significance in terms of time and security. The time part is done; as for the security part,...