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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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Can one design an asymmetric encryption scheme based on any secret sharing scheme? Are they that closely related?

I've seen both asymmetric encryption and secret sharing schemes based on graph 3-coloring, and I'm curious if this is a coincidence due to some peculiar property of graph 3-coloring alone.
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How to encrypt the truth table in garbled circuits?

I'm learning about garbled circuits, and I'm using the following tutorial: Yao's Protocol. I have a questions regarding to construction (encryption) of truth table in garbled circuits. Slide 14 says:...
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What is different below two Ciphersuites?

I have two questions; I need an explanation for the differences of below two cipher suites. How do they work with SSL/TLS protocol? (my main concern first one doesn't have '...
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Multiple encryption using the same key

I am a newbie to this area. I have a program that uses a custom algorithm to encrypt a message. I can encrypt it as many times as I want, but using the same key. I have couple of questions so that I ...
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Encrypt a file in a way that decryption requires every recipient's cooperation

The best related concept I can think of is the two-man rule. https://en.wikipedia.org/wiki/Two-man_rule. To put it simply, n people are required to give their authorization before a system / secret ...
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Can modular multiplicative inverse be used to create a secure cipher?

Let $N$ be a large number; and $(e, d, N)$ be a secret-key; where $e$ is a one-time random factor, and large enough (say the more or less the same number of bits as $N$), where $e < N$ and $e * d \...
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Key-space analysis of an algorithm

I have an algorithm that requires a set of keys to encrypt a text (image of size N x N). It is an image encryption algorithm for a project. The key can be thought of as a tuple $x_0, \lambda, d, i, ...
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feistel cipher and number of rounds

In feistel cipher , does it matter that number of rounds be 16 ? is using 16 rounds will give the best result ? Or using any number of rounds is the same? in cryptography and network security by ...
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Question on nCPA Security and Uniform Permutations

I feel I am misunderstanding the idea of nCPA security and its relation to uniform permutations. In particular I've been reading the paper "Hoang, Morris Rogaway; An Enciphering Scheme Based on a Card ...
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How safe is a book cipher? How would you break it?

This might not be a very specific question, but I was wondering this morning. If one were to encode a message by making a string out of an entire book and writing the message by searching for a random ...
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1answer
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Are the following asymmetric encryption schemes equivalent?

Consider the scenario where you want a machine to be able to send daily encrypted backups to a storage server. You'd prefer to not use simply a symmetric key for encryption, because if the machine ...
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2answers
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How secure is ChaCha20? [closed]

I want to implement a stream cipher to encrypt very sensitive data in my Python code. I heard about the ChaCha20 algorithm and the PyCryptodome library , but how secure is it ?
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Attack on stream cipher that XOR's the output of two LFSRs

There are two LFSRs of different lengths: LFSR-17 and LFSR-25. LFSR-17 Initially contains a two byte seed, with a 1 injected into the fourth bit, for a total of 17 bits. LFSR-25 operates in the same ...
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How can a XOR encryption be cracked systematically?

It's given that a string, encoded in hex format, is obtained by XOR encryption of a plain text and a key. The key is unknown (not even the length). What are the ...
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Why does the Content Scrambling System have two different length LFSRs

CSS uses two LFSRs of length 17 and 25. If we have two periodic functions $f(t)$ and $g(t)$ and consider the function $h(t) = (f(t), g(t))$, then $h$ will have period $pq/\gcd(p, q)$ where $p$ and $q$...
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Finite Automata and Application to Cryptography

The automated inverse theory in cryptography, points to autonomous finite automata, which is relative to the canonical form for one-key cryptosystems based on finite automata, the public key ...
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Encryption wth expiry date

Is there a way to encrypt a file with expiry date? I want to share a file which can be decrypted using a key until certain date. After that date, the recipient should not be able to decrypt the file....
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Encryption using deterministic CSPRNG as secure as CSPRNG

As a beginner it seems that a scheme derived from a CSPRNG should be as secure as that CSPRNG. Is this a correct assumption? Are there restrictions or known special cases? A rough outline would be: ...
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Encrypting/Decrypting sensitive information for storage purpose

I want to store account numbers and routing numbers into SQL database, and i was looking for best way to encrypt/decrypt this sensitive information. After researching i found i can use symmetric (like ...
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3DES Feasibility and Security [closed]

Questions are as following: Is 3DES still feasible (in terms of security and performance) to use? Is 3DES safe to use in ECB mode? Every time on giving the same input (plain text) to encrypt via 3DES ...
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1answer
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Is there any valuable Cryptography certification for working in the field? [closed]

I'm an amateur math/crypto/CS passionate, but I find myself without any degree or certification that gives credit to my skill-set, specially on math and crypto. Currently I'm designing cryptosystem on ...
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1answer
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Login security and plaintext of a password stored in Argon2i to derive a key via halite safe?

I'm using Symfony 4. I have set parameters on all my Argon2 stuff below so that it takes 1s per iteration. This website is supposed to encrypt HIPAA information. Basically I have a table like this <...
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Do I need to know the curve for ECIES decryption?

Let's assume that I have key pair generated using the following curves: brainpoolP256r1, brainpoolP320r1, brainpoolP384r1 or brainpoolP512r1. Do I need information which curve was used to decrypt ...
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Can a digital signature scheme also be an encryption scheme?

Using Schnorr signatures, one could devise a system where a single public key can represent multiple signers. Do signature schemes like that represent crypto systems usable for encryption? In that ...
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Is it Ok to reverse the usage of public key and private key

Well things like this, my coworker suggest exchange the private key between server and client and using public key to decrypt message privately, his reason is, this is just the same as normal usage, ...
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permutation cipher definition unclear

I have an assignment to decode a permutation cipher based on a key. But on the internet I found only ONE website talking about it. Things are not very clear. I understand that I have to reorder the ...
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1answer
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RSA: Private key given public key, plain text, and cipher text with no padding?

Are there attacks which will return the RSA private key when the attacker knows the public key, plain text, and cipher text when no padding is used in the RSA algorithm? If yes, what are the known ...
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2answers
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Public key encryption and decryption with private key [closed]

I am learning cryptography and here is what I understood so far: Story. I decide to talk with my friend over unencrypted channel. We exchange public keys with each other so that we can encrypt ...
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Differences between industrial and military cryptography

Basically industrial and military cryptography should follow same rules but what does makes it difference between these two: Higher key length, unknown protocols to civil or isolated transferring ...
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1answer
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Keys: Is This Way of Encryption Already Invented?

I've invented a way of encryption where there are keys which represent a certain cipher alphabet, whether it be a scrambled alphabet, shifted alphabets, numbers or symbols/pictographs. For example, ...
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1answer
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Global minimum based cryptography?

When using the Back propagation Algorithm for Machine Learning, it is often said finding the global minimum of a cost function over $\mathbb{R}^n$ is very hard, and as $n$ increases it gets even more ...
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End-To-End encryption for VoIP teleconference applications and many-to-many lag-sensitive applications

There are various protocols that allow you to have privacy-enhanced chat. Those can be either 2-party chat such as: OTR SIGNAL or multiparty chat such as: SIGNAL (n+1)sec mpOTR GOTR (2013 spec and ...
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Is Rfc2898DeriveBytes random? C#

I am trying to wrap my head around encryption in .NET. I am trying to implement a simple solution in ASP.NET Core to encrypt a cookie containing some non-meaningful numbers to outsiders. I need to be ...
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Can we encrypt data that must be decrypted with any private key plus a server generate bits?

I have come up with a scenario to make a secure data. Suppose I have a public encrypted file that anybody can download. But whenever anyone want to decrypt that data they need to get a key from server ...
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1answer
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Playfair cipher - questions about inserting 'X'

I'm implementing the Playfair cipher as part of a programming project. I realize there are different versions of the cipher - I've been asked to implement the version which treats the letters 'I' and '...
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1answer
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Does DROWN attack break 2048-bit key itself or just the plaintext encrypted with the RSA key

Does the DROWN attack enable breaking strong RSA keys (e.g. the 2048-bit key itself) or enable breaking the plaintext (i.e. pre-master key) that is encrypted with a 2048-bit (or any strong) RSA, if ...
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DES- If LSB is removed, are the key B and C the same?

I believe that in DES every 8th bit is ignored of the key. That means B and C are same if the LSB is ignored. So, shouldn't encrypting a message by the key all Bs be able to be decrypted by key with ...
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1answer
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RSA Time Complexity on Best Case, Average Case and Worst Case

I am currently learning the work arounds about RSA algorithm. I wanted to know the time complexity of the encryption part and decryption part on Best Case, Average Case and Worst Case. Im new in ...
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Why are there so many versions of the TEA block cipher?

Why are there so many types of TEA, for example TEA, XTEA, and XXTEA? What are the differences?
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XOR of users password Scrypt key and Random 32 bit salt?

I am trying to encrypt users private keys with the user password but if a user provides a weak password then the scrypt key generated from it will also be weak and suspectible to attack. Let say the ...
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1answer
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Conjugate variables in Quantum Key Distribution?

According to Heisenberg's Uncertainty Principle, it is impossible to measure the values of conjugate variables simultaneously as measuring one accurately would make the other equally corrupt. So in ...
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What is the role of steganography in network security?

Quick definition: Hiding secret messages inside what seem to be harmless messages is nothing new. The word steganography itself originated in Greece and means “covered writing”. During important ...
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Authenticated encryption vs end-end encryption

I am kind of new to crypto. can someone highlight the differences between authenticated encryption and End-to-End encryption
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What is the purpose of Homomorphic encryption? [closed]

Homomorphic cryptography is a kind of cryptography that allows you to do special math operations on the ciphertext, and the maths performed are identical to the obvious ones. For example, one person ...
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1answer
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Oblivious Encryption: Oblivious Transfer Based Encryption

I’m aware of a couple of OT protocols, most of which use Public Key Cryptography, Key Establishment (or similar constructs) as the base. I don’t really have specific knowledge on other OT protocols, ...
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How is GCM Parallelizeable? [duplicate]

The Wikipedia article on GCM says GCM can take full advantage of parallel processing. I had thought GCM uses a random IV for the first block, then for the second ...
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How does Skype hash the phone number to a fixed length? [closed]

I have a Skype account with a phone number and I noticed that my contacts and I who created the accounts with a phone number have the Skype ID in some form of a hash. But all the Skype IDs have the ...
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Signal: Ratchet & Message History

Hi folks– new to cryptography. My understanding of the double ratchet algorithm (or even just any ratchet algorithm) is that it uses all of the previous state (in Signal's case, all the previous ...
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One-time pad encryption of ASCII characters

I can't understand a question I came across in a course. You observe three ciphertexts all resulting from encryption of ASCII plaintexts containing English letters and spaces only, using the ...
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Is AES easier to crack when the input is small?

Say you just want to encrypt a number. For example, say the number could be any double. A double in C# and Java is 8 bytes. If you were to encrypt a double using ...