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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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. (each of those planes is cyclic in two orthogonal directions, like a torus) Given ...
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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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Are PKI PQC algorithms slower than their nonPQ counterparts? (e.g. NTRU vs RSA)

Are the methodologies (hard problems being used to secure the encryption) in post-quantum algorithms inherently slower than what we have right now? If not, why weren't they used initially?
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What are limits of Modulus Switching in BFV encryption?

I want to understand the limits of modulus switching in BFV. Lets assume $q$ represents ciphertext modulus and $t$ represents plaintext modulus. $q$ is set to a $60$ bit value and $t$ is set to $20$ ...
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Does encryption of many files shorten the list of possible passwords?

Hopefully this question is not duplicative, nor its answer too elementary. Suppose I have a file. I encrypt it, using a password. The password presumably stipulates a pattern or relationship between ...
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Is there something like a node network with more than 2 edges/neighbors in cryptography/encryption?

Many types of encryption can be generalized as using a message $m$ and a key $k$ as input of an encryption function $f$ with a cipher $c$ as output. $$f(m,k)=c$$ As a node graph this could look like ...
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What is Relationship between ciphertext quotient and polynomial degree in RLWE?

In Ring Learning with Errors problem, the size of the ciphertext quotient $q$ decides the size of the polynomial degree $n$ or vice versa. In other words, rlwe problem is hard only when the polynomial ...
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Encryption using Playfair algorithm

how to encrypt using play fair if "i , j" both are in the plaintext? for example Beijing.
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RC4-40 with IV (32-bit) setup

I have taken this implementation of RC4 written in C. I have 40-bit key and 32-bit IV (both in hex). So, questions is about KSA step: How should I transform hex key value into the char array? Just ...
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How to derive two keys from one password with Argon2id

I'd like to derive two independent 256 bit keys for symmetric encryption from a user password. I'm using Argon2id as the password-based key derivation function. I'm planning to do the following: ...
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Looking for an approach (and made one!) that is very small and simple code, but uncrackable

I'm looking for / working on an algorithm that must be very small and simple, with no extra libraries and stuff that looks suspicious to a user using the code. You can see what I mean by reading the ...
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How to find strength of a cryptographic hash function?

I am having an idea to create a cryptographic hashing algorithm. I found a mathematical function $f: x \rightarrow y$ . By using Merkle-Damgård construction wide pipe, I designed a hashing function. ...
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Indistinguishability proof of an encryption scheme

Is there any indistinguishability proof (e.g., IND-CPA, IND-CCA, IND-CCA1, IND-CCA2, IND-CKA) based on games that involve breaking the AES security? Usually the proof involve breaking hard problems ...
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What does "ECDHE_RSA" mean? [duplicate]

Hey i do have a question about cryptography: I know that Elliptic curve is cryptography algorithm and Diffie–Hellman is mechanism which is provide the two parties who wish to encrypt some data with a ...
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Get Pixel Data from JPG/JPEG but still bring the integrity? [closed]

As far as I know, JPG is a lossy image compression format Meanwhile, BMP is a generally uncompressed image format, whose file structure consists of bitmapFileHeader (14 bytes) and bitmapInfoHeader (40 ...
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Tools/libraries to protect private keys using shamir secret sharing / multi-party computation?

here is the scenario. I want to use the concept of shamir secret sharing (or other multi-party computation methods) to store my private key in the public-key encryption. For example, I use RSA to ...
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Using the hash of the plaintext as the key

I want to start off by being very clear: I'm not designing a system around this, this is 100% a hypothetical I was toying with. Is there any harm in using the cryptographic hash of a plaintext as the ...
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How could unbreakable encryption be used?

I'm part of a team of students from the Vienna University of Economics, which have the task to find application fields for a new technology. The technology itself is provided by an external partner, ...
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Is it possible to use PGP subkeys in multiple emails without correlating them?

I would like to know if sub-public keys of PGP keys can be published separately, if I create a pair of master keys and multiple sub keys to be used in multiple emails, and normally use only the sub ...
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How can symmetric encryption be used to create a digital signature? Is it even possible?

I want to use symmetric encryption to create a digital signature. What can be the possible scenarios where symmetric encryption is used to create digital signatures?
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What is "entropic security"?

I've come across a form of cryptographic security that I've never heard of: entropic security. I've read the Russel et al abstract and that doesn't seem to bear much relation to the wiki article. ...
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Let negl1 and negl2 be negligible functions [closed]

can we still consider the second function negligible ? is there any main differences between them?
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Why can't rsa come out with the same cipher?

When $x < N$, there cannot be the same encrypted message with different outgoing messages. But why?
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OFB mode discussion

In OFB mode, I understand that a bit flip in $c_i$ for $i > 0$ only causes a bit flip in message block $m_i$. However, how is it possible for a bit flip in $c_0$ (i.e, in IV) will result in all the ...
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limiting number of queries to Enc. or Dec

Why do we limit the number of queries to Encryption or Decryption oracles in the security analysis of various encryption schemes to be polynomial in the security parameter n?
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calculate a tag of CBC-MAC

with a block cipher having a 256-bit key and 128-bit block length to MAC a 1024-bit message. How many evaluations of the block cipher will be performed to calculate the tag? [Assume there is no ...
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Confusion of message space and key space

i just a bit confused that is it reasonable to assume that the probability of sending message $m \in M$ is uniformly distributed over the message space $M$? How is this different from assuming that ...
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RSA Encryption and ECDH in OpenPGP

According to RFC4880 standard 1.Refer to section 2.1 Confidentiality via Encryption --> OpenPGP combines symmetric-key encryption and public-key encryption to provide confidentiality +To protect ...
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Distributing the Master Public Key in Identity-based Encryption systems

I was just wondering how the private key generator should publish the master public key inside of an IBE system. This key is needed for all devices in the network to derive the public key of receiving ...

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