Questions tagged [encryption]

Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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Creating a Password Generator using CSPRNG in React JS

I am building a password generator website using ReactJS (link). I have read a lot about various ways of generating cryptographically secure passwords and I have decided to go with using CSPRNG. I don'...
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Sending encrypted message without public key from recipient (elgamal)

assume Bob and Alice use Elgamal encryption scheme. Alice wants to send Bob a message, but does not know Bobs public key. Is there a way for Alice to find out Bobs public key by receiving multiple ...
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Diffie-Hellman: how to solve an alternative of Diffie-Hellman given an algorithm that solves Square Diffie-Hellman?

A simple question. How can I proof the next polynomial reduction? : $DH’ ≤_{p} SQ$ where DH': given $g^{a}$ and $g^{b}$, compute {$g^{ab}$,$yg^{ab}$} where $y= g^{d/2}$, d is the order of cyclic ...
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What is a ciphering key?

In Hebrew language there is the term tzophen (צופן) which means cipher. There is also a term "maphtech hatzpana" (מפתח הצפנה) which means "ciphering key". What is a ciphering key? ...
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What is the difference between AES-CCM8 mode and AES-CCM mode?

I know AES-GCM and AES-CCM but what is the difference between AES-CCM8 mode and AES-CCM mode ? Is it the length of the cipher?
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Alternative to CBC mode encryption?

Given that CBC mode encryption is vulnerable to padding oracle attacks, what is the next best alternative ? a) Include a hash check in the API scheme, validate the hash and then proceed with CBC. If ...
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Simple scheme to publish data with a private key

The goal is for Alice to send an encrypted message to Bob. Neither Bob nor anyone else should be able to decode the message. Alice should be be able to decode it, when all data is shown to her. ...
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How to quantify privacy, when using homomorphic encryption?

How can you measure how secure or private the new variables are relative to the real (actual) variables. I want to compare homomorphic encryption and differential privacy in combination with machine ...
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Is PRF Xored (or multiplied) with a random number still a secure PRF?

I've know that a PRF Xored with its key is not a secure PRF. Then I wonder that what if the Xored (or multiplied) item is another random number. The formal expression is as belows: Let $F_k(x):\{0,1\}^...
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Classical vs Quantum-Safe Algorithms and Protocols / Application Approach

Various proposals are being explored for X509 V3 certificates in a Post Quantum Cryptography (PQC) world. Currently, these include just having a certificate for classical and PQ, having a hybrid ...
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Encrypting RSA with a 2 part key [migrated]

I'm writing an audio program in c++ with the juce framework and I'm able to successfully encrypt and decrypt. Juce has a function CreateKeypair: https://docs.juce.com/master/classRSAKey.html in the ...
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A CERTIFIED DIGITAL SIGNATURE paper pg 20 - 25

Reference paper: "A CERTIFIED DIGITAL SIGNATURE" With reference to the image above which is from Page 20 of the attached paper. What is this new protocol that the paper speaks of here? What ...
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Synchronized random number generation

Let me try to reformulate the problem, as it might help a bit. The requirements are the following: At the beginning of their connection, the two end-points perform a Diffie-Hellman to derive with a ...
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How do different types of ciphers relate to each other?

I understand that there are symmetric and asymmetric (public-key) cyphers. The first have the same key used for encryption and decryption, while the second use a public key for encryption and a ...
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How $f(x)$ set in ring-lattice crypto?

I want to clear out some confusions I have about Lattice crypto. As discussed in this talk Signatures, Commitments, Zero-Knowledge, and Applications For ring $Z_q[x]/f(x)$, I want to understand ...
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What does prevent a hacker to calculate signature from message and public key without using private key? [duplicate]

I am talking about the process in the image: Everyone is saying this process is safe and and what I am claiming is impossible, but common sense says different.
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Which cipher is more secure TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA or TLS_RSA_WITH_AES_256_GCM_SHA384?

TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA supports forward secrecy but it doesn't use GCM mode and use SHA1 TLS_RSA_WITH_AES_256_GCM_SHA384 uses GCM mode and SHA2 but it doesn't support forward secrecy. ...
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What would be the consequences of using a IV smaller than the block size in CBC encryption?

Here I use a Threefish kernel module with CBC mode. But there is no hash function that can supply a IV with Threefish block size (1024-bits), so I use a 64-bit random IV inserted in the dm-crypt with ...
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Questions on "A CERTIFIED DIGITAL SIGNATURE" Pg. 19

Referenced paper here. The above excerpt is from Page 19 of attached paper. I have a few questions. y = F^9(x) is equivalent of F(F(F(F(F(F(F(F(F(x))))))))) ? The excerpt says that this allows us to ...
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Relation between oblivious linear function evaluation(OLE) can be used to build a PSI protocol

I read somewhere that oblivious linear function evaluation(OLE) can be used to build a PSI protocol. Is there any link between these two primitives?
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Close to hexa ciphers [closed]

Basically this post was about a cipher with a trailing "=" Any idea is welcome :)
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Cryptography based on #P-complete problems

Are there any examples of a cryptographic scheme based on (an average-case form of) a #P-complete problem?
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Schnorr signature | Schnorr Public Parameters

hello guys hope you are doing well :), i am trying to simulate the Schnorr Signature, but i have encountered some difficulties finding the generator, i have chosen a prime P of 1024bit and took a ...
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RSA: Obtain private key exploiting badly generated public key

I have to solve the following problem: What I have: $n$, a 2048 bit number What I need to find: $p$ and $q$ such that $n = p\cdot q$. What I know: With $p_1$ the first half of $p$ and $p_2$ the ...
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Online/offline times of Key Distribution Center and Certification Authority

In comparing the merits of a Key Distribution Center or KDC versus a single root certificate authority public key infrastructure or PKI, is it possible for the KDC to be online at all times whereas ...
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Discrete Logarithm Based algorithm

The private (secret) key in DL (discrete logarithm) based algorithms is uniformly selected from the group Zq*. This private key is then used to compute the public key. Could the opposite be done, for ...
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Secretly compute multiplication of two numbers owned by two people

For example, Alice and Bob have two numbers $a$ and $b$, respectively. They want to calculate the multiplication $a\cdot b$ without Alice knowing $b$ or Bob knowing $a$ and send this multiplication $a\...
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ElGamal-based BBS proxy re-encryption implementation?

are there any available tools/libraries that implement the idea of EIGamal-based proxy re-encryption scheme shown below? Preferably in Golang. Thank you! Source of this picture: https://www.cs.jhu....
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multi-user deterministic symmetric encryption

I was wondering whether there exists a symmetric encryption scheme such that there is 1 sender and n receivers. Each receiver has 1 random and independent symmetric key. The sender knows the ...
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Public-key/asymmetric encryption where you can only leak the decrypted message by leaking your password

A bunch of friends are using public-key encryption to send encrypted messages to each other using an open public forum. I.e. each friend has a public key (which you can use to encrypt messages for ...
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Best way to encrypt sensitive data on server with HSM and symmetric keys

I need to store sensitive data (like customer photos) in a SQL database in the most secure way in case of security breaches. The data won't be accessed by the clients, only to internal processes that ...
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If I sign-then-encrypt a JWT, how does a 3rd party validate that the JWE message is valid?

Since it is preferred to sign-then-encrypt I was wondering how can another party validate that the message is valid? The use case I had was the following... Client authenticates and gets the access ...
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A doubt in pairing based cryptography

I have seen authors taking $G_1=G_2=G_T=G$ to be the same group of prime order $q$. What I know is that for pairing of type $$e:G_1\times G_2\rightarrow G_T,$$ size of the element in the target group ...
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Historical key sizes for RSA and discrete log [closed]

What is the historical pattern for key size increases for rsa vs discrete log? What are the current and future projected sizes for these?
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Bleichenbacher attack equation

In the Bleichenbacher attack, when the $|M_i−1| = 1$, we should choose $r_i >= 2(bs_{i-1} -2B)/n$ in order to increase the search performance. I don't quite understand how this $r_i$ value is ...
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Why there is so high computational cost of multiplication in Microsoft Seal?

I was doing some Microsoft Seal testing on my macbook pro (i7) and got following results Coefficient mod $q = 100$ bits and Polynomial degree $n= 8192$ Ciphertext-Plaintext multiplication takes 0.211 ...
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RSA Algorithm: What are the maximal possible locks that your friend can have so that he/she can secretly share that to you?

I found this question while preparing for exam. The question is Q)Suppose, you and your friends have a few numbers of locks and you all want to share that numbers among yourselves securely using RSA ...
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predict random keys using python [closed]

How can I write a program in python to predict the random key (urandom) that is used for encryption? I tried to search and I couldn’t find anything related to guessing and predicting urandom in python
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Generating multiple keys to decrypt one encrypted file

I've come across this particular design where I have one file encrypted. Then multiple people may want to access the file and I want to generate an individual key for each person, but each individual ...
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EC Public key encryption scheme where Alice does not know Bob's public key

I've found ECDH and ECIES, but those both require Alice to know Bob's public key and Bob to know Alice's public key in order to derive a shared secret. Now assume Bob knows Alice's public key $A$, but ...
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Encryption of message concatenated with encrypted message

Is there a possibility to encrypt a message that is a concatenation of an encrypted message and another message ( encrypt_message + message )?
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What is minimum size of polynomial modulus in Seal implementation of BFV?

Is there a way to get flexible parameters in Seal for batching? The issue is that for polynomial mod $n=4096$, the function I am computing has a multiplicative depth of $3~4$, to handle noise growth I ...
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Which is the smallest, cyclic in 3 directions, consistent structure of random values which can be hidden at the adversaries machine? (some comparison)

Or more general each member can be part of up to three 2D locally euclidean planes of 2 different dimensions. (each of those planes is cyclic in two orthogonal directions, like a torus) Given just ...
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How to understand noise growth in BFV?

I am trying to understand the noise growth due to multiplication in BFV encryption. As explained in section 4 and equation 3 of this paper: https://eprint.iacr.org/2012/144.pdf. I couldn't follow what ...
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Devising a Feistel cipher in which the subkeys are constructed badly so that a meet in the middle attack will compromise its security

I'm trying to find a Feistel cipher in which the subkeys are constructed badly so that a meet in the middle attack will compromise its security. I thought about trying out a cipher where all the ...
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Is there a way to modify an existing RSA key pair so that the functionality remains?

I have an existing RSA key pair, how to 'derive' a different key pair based on the existing one so that the encryption decryption functionality remains but the original key isn't interchangeable with ...
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Separate Messages Encryption

In a public key system, Alice sends Bob separate messages telling him information about the time T and place P they would meet, encrypted with Bob's public key. What is the most secured protocol: <...
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Would this hash based encryption algorithm work in theory?

I was just thinking about this and couldn't seem to find anything on it online. So the idea I had was this: Generating a random key of some length. Then hashing this key with SHA256 (or something of ...
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Can you really ignore number of quantum processing steps needed for Shor's algorithm?

Answers to question RSA key length vs. Shor's algorithm suggest that e.g. 2048 bit RSA encryption would be trivially broken with 4099 qubit quantum computer using Shor's algorithm (best known ...
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Entering a word in a S-Box (like Feistel ciphers do) and keeping the S-Box secret: Could this be called encryption?

Let's suppose I take a data block of 64-bits and use it as an entry in a (big) S-box, and keep the S-box secret. S-box would be the "key". For "decryption" I just enter the result ...
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