# All Questions

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### Is chaos based cryptography quantum-resistant?

recently I'm learning chaos based cryptography, but it confuses me that whether concrete implement such as chebyshev map-based encryption algorithm quantum-resistant?
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### Make substitution cipher less easy to decode

What methods exist to make frequency analysis and other attacks on substitution cipher harder to pull? For example: Polyalphabetic: Alternate the substitution of frequent letters or words, so "E" can ...
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### Unknown bit in the output of encryption of data using SIMECK32 cipher?

How is the unknown bits (annotated by red arrow in figure below) come in the OUTPUT after round 1 and round 2 ? Following is the pictorial representation of SIMECK round function operation. Ref: ...
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### With node-jose, Should I expect the JWK -> PEM conversion to be reversible?

I am using node-jose to convert a particular JWK to a PEM, and then ... converting that PEM to a JWK. The resulting JWK has the same e, but different n than the original. Should I be surprised? I ...
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### Identifying encryption & decrypting strange numeric code [closed]

This following encrypted message was posted in my town and me and some friends are trying to solve it but cant come to any conclusions. The message is as follows: ...
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### Node.js: I have 16 byte key. How can I generate 32 byte key from 16 byte key for AES-256-CBC

I am trying to do decryption in Node.js and encryption in C# with AES CBC 256. I have 16 byte key. I need 32 byte for AES CBC 256 method in Node.js. I tried using Buffer.alloc(32,16-byte-key). I keep ...
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### Encryption algorithm [closed]

I do not have much knowlegde about cryptography. Can anyone please help me to answer this question: Having just completed a course in cryptography, Tom and Jerry start a new business to manufacture ...
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### Is an implementation of blinded encryption/decryption mechanism exists?

I want to use 2 semi trusted servers, to decrypt a secret for a user but I don't want those servers to have access to the plain text. Those server need to be able to "partially" decrypt and let the ...
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### When using Ristretto or Decaf with Ed25519 and Ed448, do scalars still need pruning/trimming/clamping?

Decaf is a point compression method that builds a prime-order group for (twisted) Edwards curves and Montgomery curves with cofactor $h = 4$ based on the Jacobi quartic [H2015]. The promise is to ...
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### How can we assure Non-repudiation without a personal certificate (eg. using ID authentication) [migrated]

I need a help to understand some specific points about non-repudiation, nonetheless I implemented some authentication methods: Digital Signature Authentication; CHAP (Challenge Authentication ...
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### RSA: Construct private / public key for given cipher and plain text message

let's say we are given a classical RSA encryption scheme, though we would like to "reverse" the task: Given two messages $c, m$ choose $p, q, e$ such that $p, q$ are prime and $c ^ d \equiv m\pmod N$ ...
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### RSA with a prime substituted by a Carmichael number

If the public key in a RSA system is $(n,e)$ with $n=pq$, $p$ prime, $q <p$ a Carmichael number and $\gcd(e,(p-1)(q-1))=1$ then if $d$ is the inverse of $e$ modulo $k=(p-1)(q-1)$, I want to show ...
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### How to show that CBC-MAC is not one way mapping? [closed]

Is it possible if the party knows the key, how can i prove that.
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### Testing speed of symmetric vs asymmetric encryption and decryption using gpg

I'm aware that symmetric is faster than asymmetric. I want to test this, but my (obviously incorrect) tests show the reverse. Symmetric test: ...
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### Creating a private cryptocurrency without trusted setup

I am interested in creating a cryptocurrency which keeps the sender, the receiver and the amount private and does not require a trusted setup. I have already read the Zerocash protocol but It uses zk-...
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### Private exponent on RSA key

this is the first time I write here. I'm studying a library to encrypt/decrypt with RSA algorithm. In an example given by the library I found this: ...
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### How to have a bound (upper or lower) of Gaussion distribution over lattice based crypto>

In lattice-based crypto, we always need to sample 'noise' from Gaussian distribution, but how to measure the bound the noise? For example, if the Gaussian distribution is D_{u,\sigma}, where u is the ...
163 views

I see Chacha20Poly1305, XsalsaPoly1305 and AES GCM usually used and mentioned in literature and implementations as AEAD cyphers. My question is that Poly1305 provide authentication and Salsa20 ...
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### I don't understand RSA encryption (specific questions)?

So I've been studying RSA for a class and I'm having a hard time understanding how it works. Why do we choose the value of e such that e is relatively prime to the totient (as opposed to just being ...
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### Trying to decrypt saml2:EncryptedAssertion (in .NET)

I'm trying to decrypt EncryptedAssertion data (SAML) in .NET Framework: ...
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### Encrypt symmetric session key with asymmetric or symmetric master key?

Every day, I must backup my server's files, encrypt the backup, and upload it to untrusted cloud storage (dropbox, s3, etc.) I've spent time on security.stackexchange where I discovered the typical ...
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### Does cryptographically-secure pseudo random generators require a secure seed?

For any cryptographically-secure pseudo random generators, do we need a secure random seed for those? If the seed is predictable, then everything is broken due to the deterministic propetry of the ...
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### Layman understanding of SHAKE128 XOF

Need some help. I am not versed in hashing and just started programming with PHP and currently need to hash some strings but required it to be unique. Found that OpenSSL can hash with SHAKE128 but ...
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### Error-Correction capabilities of encryption?

This is motivated by this question about the recovery of (corrupted) encrypted files, and in particular the statement (in the answer): But If I know the algorithm and the key and I make a custom ...
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### Point-halving/solving quartic equations over the elliptic curve E(Z_N)/ring Z_N where N = pq

I am wondering whether there are any results/whether there is any knowledge about the following problem: Given a univariate polynomial (say, a quartic) equation defined over $\mathbb{Z}_N$, is it ...
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### Safest alternative for hashing credit card numbers to use the hash as fingerprint?

Same question asked here in 2014 but since a lot has changed since then, I would like to get feedback from experts on the latest best practices. The problem Our requirement is to provide the ...
28 views

### (Cracking RSA) How to calculate the Private Key using Public key, p,q,r,n?

I have been given the following values : ...
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### Does Encryption add difficulties to File Recovery?

Seems Yes. People always tell us, it is very hard (or almost impossible) to recover an encrypted hard disk. But after a second thought. I think this is not true. Given that we know the KEY, and the ...
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### Suppose $H(X) \rightarrow Y$ is collision resistant. Is $H$ also one-way?

If we have $H(X) \rightarrow Y$ and it is collision resistant. Can we say that $H$ is also one-way? And if that is true can you give me an example?
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### Can hashes be used to generate larger random numbers?

As far as I understand a hash transforms data into a fixed length representation. For example, a random function returns 8-byte numbers and a hash function has a block size of 32-bytes. If I now ...
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### Does splitting random data reduce its security?

Let's say I've got some securely-generated random data I want to encode as words, 32 bits of it. My wordlist is 2048 words, so each word encodes 11 bits of information. I write a routine to pack ...
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### Verify ECDSA signature without data

With RSA PKCS#1 v1.5 it is possible to verify that the signature was generated by the correct private key without actually having access to the data. You just perform the modular exponentiation with ...
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### Can an AES-GCM be cracked if the key is known but the nonce isn't?

I'm kind of new in this field and I've been trying to learn it. I'm now facing an issue where I have a couple of packages encrypted with AES-128 GCM and I have the key that was used to encrypt these ...
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### How to backup a secret encrypted by multi parties without revealing the secret?

I'm searching for a way to backup a secret that only the end user knows the information with 2 trusted hosts. But trusted hosts shouldn't have access to secret at any time. First basic version : ...
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### Can there be more than one valid private exponent for a given p, q, and e in RSA encryption?

For example, given: p = 173, q = 149, e = 3 Using phi(n) gives d = 16971 While using lambda(n) gives d = 4243 Both values satisfy the checking equation (de)%phi=1, so are both correct, and if so, ...
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### How does re-hashing affects security strength?

I am currently saving hashed passwords for my website. Passwords are salted and then hashed using SHA3-512. I understand the security level of SHA3-512, as it is for all Keccak algorithms, is half the ...
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### Anonymous location hashing

Is it possible to know if two geographic locations are within a certain distance of each other without revealing the location? I'm thinking about contact tracing during the COVID-19 outbreak. ...