# All Questions

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### Key sizes for discrete logarithm based methods

I have a question regarding the key generation process of methods that are based on the discrete logarithm problem. This site gives some good insights, but I don't fully grasp it I think: ...
52 views

### What security authorities and standards reject $e=3$ in RSA, when, and with what rationale?

In RSA, some security authorities and/or standards allow the public exponent $e=3$, others require or recommend $e>2^{16}$ (or perhaps some other minimum). I gathered the following: PKCS#1 allows ...
145 views

### How random are comercial TRNGS

I'm thinking about buying an USB TRNG. The question is: How do I evaluate it's randomness ? I'm sure some are better than others but which is which ? Are thermal-noise better than radio-noise TRNGs?
111 views

### Recommended skills for a job in cryptology

First let me apologize if this is an ill posed question. Let me also note that I do not in any way seek a comprehensive answer, simply your thoughts on what makes for a valuable asset to a company ...
34 views

### sir,please suggest me an algorithm or method how can i improve the prediction based encryption method using randomization?

I am doing research on security for data migration in cloud computing. I have gone through many encryption algorithms to secure data for migration, but I want to create my own algorithm that could be ...
84 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 ...
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### How do I create a self-signed S/MIME signing certificate with OpenSSL and then sign a file? [migrated]

I would like to create a certificate with OpenSSL and then use it to create an S/MIME format detached signature of a file. Is this something that makes sense in the context of S/MIME? How do I get ...
108 views

### Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages

I've been toying with some encryption scenarios recently. One of the hard ones I came across is a multi-party system. So we have Bob -- The person who sends the message (and knows it's recipients) ...
73 views

### Proper Way to Encrypt Data with Two Keys?

I'm going to develop a system that will have two keys. One supplied and generated by the system that's specific to an individual user and one from the user. I plan on using AES. Does it make sense ...
28 views

346 views

### Selective format-compliant JPEG encryption?

I am working towards building a format-compliant encryption system for pictures. The aim of it is to be able to obscure specific areas of a picture (i.e. faces, car license numbers...) while keeping ...
103 views

### Is this a sensible cryptographic protocol intending to reduce the impact of compromised security?

I'm in the process of designing a cryptographic protocol which will reduce the impact an attacker will have if they gained root access to a server storing data. The basic crux of it is that keys ...
85 views

### Generate fixed length cipher text from arbitrary length plaintext

Using an encryption algorithm like AES, is it possible to generate a fixed length cipher text no matter how long the plain text becomes?
113 views

### Generating IV in TLS 1.2

I'm writing a TLS 1.2 implementation (in C#) using a custom protocol. My question is how to generate the IV attached to each message, I don't want to use RandonNumberGenerator because I've heard it ...
120 views

### Help me describe/identify this challenge-response protocol/algorithm?

My area of expertise is reverse engineering, specifically embedded systems. I do attack cryptographic systems, but this largely involves key recovery or exploiting the implementation. I was asked to ...
159 views

### SHA-1:Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output?

Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? What is the probability that a 160-bit SHA-1 hash output contains at least 128 1's?
162 views

### Understanding Feldman's VSS with a simple example

I'm trying to understand Feldman's VSS Scheme. The basic idea of that scheme is that one uses Shamir secret sharing to share a secret and commitments of the coefficients of the polynomial to allow the ...
67 views

### Is Functional Encryption about Access Control over encrypted data alone?

Informally, In functional encryption system , a decryption key allows a user to learn a function of the encrypted data. But all i see is that the function acts as an access control over the data. ...
104 views

### True random numbers generated by sensors

Is using sensor raw data a good way of generating true random numbers? I mean using an IPhone's gyro/accelerometer raw output as a base for generating an array of true random numbers.
1k views

### How to solve MixColumns

I can't really understand MixColumns in Advanced Encryption Standard, can anyone help me how to do this? I found some topic in the internet about MixColumns, but I still have a lot of question to ...
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### pseudo random sequence and permutation functions [closed]

Iam doing my Master thesis in enhancing of an encryption algorithm by using of a pseudo random sequence generators to create a 16*16 shared table and apply a permutation function on it. one of the ...
33 views

### calculating beta for elgamal elliptic curves [duplicate]

Suppose we use elgamal elliptic curves for secure communication. Bob selects a prime $p$, an elliptic curve $E$, a point $\alpha$ on $E \pmod p$, and a secret integer $f$. Suppose that Bob has ...