# All Questions

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### When is AES chosen instead of a stream Cipher (e.g., RC4) during an SSL connection?

During an SSL handshake, the browser sends a list of cipher suites to the server, from which the server selects one option. For data encryption, two of the several possibilities for the ciphers in ...
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### Homomorphic Encryption operation for regression

I must be missing something, and I am sorry if this is a novice question... I have seen in places (eg. https://crypto.stanford.edu/~dwu4/talks/SecurityLunch0214.pdf page 13) that linear regression is ...
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### Acceptable condition for dictionary search

I am trying to write a program to break transposition cipher using dictionary search. But I cannot understand the finishing condition of the search. Is there any theory that the maximum number of ...
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### On the security definition of password-authenticated key exchange

I found in all PAKE papers, the security is defined as something like this: Let $Succ(A)$ be the probability that an attacker $A$ successfully distinguished the session key from a random string. Then ...
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### Replacing signer with simulator

Assume we can prove security of digital signature scheme against key-only (no message) attacks. Now we want to prove security against adaptive chosen message attack. We use random oracle model. The ...
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### Verifying Without Knowing Key

Say user Bob sends an encrypted message to a server. People can download the message from this server and later get the key directly from Bob. Is it possible for the server to somehow verify that ...
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### ED25519 and hierarchical deterministic wallet

I'm building a solution based on the stellar codebase and using the ED25519 curve for the signatures. One of the features I've been adding to the system is a support for hierarchical deterministic ...
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### PRNG output with truly random noise

I am considering a situation where an adversary does not have access to the $n$-bit output string of a PRNG, but instead receives a noisy version of it, where each bit of the string is flipped with ...
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### How to forge signatures in the Schnorr scheme if $r=g^k$ is eliminated?

I need some help to demonstrate how to forge signatures in the Schnorr scheme if I eliminate the random string $r=g^k$ used in the hash – using $H(M)$ instead of $H(M||r)$. How would one be able to ...
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### Salary Negotiation Problem

Imagine Alice is applying for a new job. Alice has an idea of the minimum salary that she is willing to accept—let's call this value A. Bob, the hiring manager for ...
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I was thinking of using different and independent password for different websites, but not storing them in some password manager so I don't need to backup the passwords. I thought I could use some ...
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### Is manually 'salting' my passwords a safe alternative to having a different password for each site? [duplicate]

It is highly recommended to use a different password for each site to prevent the breach of security of one site from compromising the user accounts on all other websites that have the same username - ...
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### How does Bluetooth pairing (SSP with numeric comparison) work?

I have a question concerning the pairing of two Bluetooth devices using Simple Secure Pairing with numeric comparison. The NIST document I am looking at states on page 14: Numeric Comparison was ...
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### What do they mean when saying that a certain value should be “super-logarithmic”?

What do they mean when saying that a certain value should be “super-logarithmic”? I've found the Wikipedia definition of a “super-logarithm”, but I'm having trouble understanding how a given value ...
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### How do ciphers change plaintext into numeric digits for computing?

For example, in RSA, we use this for encryption: $ciphertext = (m^e \mod n)$ and for decryption. If our message is "hello world", then what number do we have to ...
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### Changing plaintext for encryption in RSA [duplicate]

In the RSA crypto scheme, the message $x$ (plaintext), is encrypted to produce ciphertext ($y$), by computing $x^e \bmod n$. Of course, that means that $x$ has to be a numeric value for this to work, ...
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### How to calculate this binary operation? [closed]

I found this binary operation, however It is the first time that I found this operator '.' : That is the equation: 02 • 63 = 00000010 • 01100011 = 11000110 I don't understand how 0 • 0=1 I ...
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### OpenSSL: Generate ECDSA key and CSR [migrated]

I know how to generate an RSA Private Key and CSR: openssl genrsa -out my.key.pem 2048 openssl req -new -sha256 -key my.key.pem -out my.csr But, How do I do the ...
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### Anyone know of a portion of the Enigma Code? [closed]

I was reading about it today and it sounds like it would be a fun thing to try to decode. Problem is that I can't find a portion anywhere. Is it classified or am I not looking in the right spots
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### Is the security of MAC function is based on HASH function

It is widely known, generally, that a MAC is a HASH with key. I just want to ensure that my understanding is correct to avoid base further assumptions on wrong conception. So, if I used MAC that uses ...
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### Easily reversible hash functions as a method of data transmission [duplicate]

I've been looking through the literature because I want to see if anyone has implemented this idea I have. I know data compression algorithms work by removing redundancy in data. I was wondering ...
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### Is unusual (non power-of-two) RSA key size more secure?

On this blog https://blog.josefsson.org/2014/06/23/offline-gnupg-master-key-and-subkeys-on-yubikey-neo-smartcard/ there is a following sentence Generate master key Below I will use a 3744 bit ...
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### DES S-Box properties

Two of the properties that lead to the design of DES S-Boxes are: For any non-zero 6-bit difference between inputs, no more than 8 of the 32 pairs of inputs exhibiting that difference may result in ...
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### How to create reduction functions in rainbow tables?

I have been trying to understand rainbow tables lately and one part is giving me trouble to understand here. Let's say I want to generate a table where the chains are 100 000 hash/plaintext long. I ...
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### Desirable S-box properties

What desirable properties should an S-box have? My current standard selection process is to just pick them at random and verify that they fit the following criteria: The probability that any random ...
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### Is the difference distribution table of AES S-box uniform?

I am studying about various block ciphers and their weaknesses, so I have a doubt about AES S-boxes, Is the difference distribution table of AES uniform ?
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### Can I discard a specific X509 signature from file?

I'm writing a program to sign files using X.509 certificates and .NET framework classes. My users can sign the same file more than once without any problem (like a revision process). So, a file may ...
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### Meaning of Policy matches when signing SSL certificates

I was going over the process of doing a self-signed SSL certificate. The config file here is one of the inputs to this process (see: https://www.phildev.net/ssl/opensslconf.html) I have a question ...