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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How to create an EC point from a plaintext message for encryption

It seems that ElGamal encryption is also possible for Elliptic Curve cryptography. However, that requires the user to convert the message to a point on the curve. What strategies are there to derive a ...
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symmetric-key cryptosystem or a public key cryptosystem [closed]

Consider the encryption scheme, where Alice chooses key $ K=(p, q) $ where $ p $ and $ q $ are primes and encrypts m using $ E_k(m) = (m + r_1p, m + r_2q) $ after choosing random number $ r_1 $ and $ ...
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Encryption algorithms that can be used for key exchange and can be eavesdropped

Which algorithms can be used for key exchange between two wireless nodes and are not secured, meaning they can be eavesdropped?
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Theoretically, what if I were to change some magic numbers in, say, AES?

Purely theoretically. I know it's a bad idea to try to invent your own encryption and that's not the intention here. Just a thought experiment. Say, I change some or all of the magic numbers used in, ...
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1answer
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how to solve discrete logarithm problem information requested

I have seen your example about ecdlp solver :The Problem is as follows: $$E\backslash GF(p):y^2=x^3+17230x+22699$$ where $p=23981$, point $G$ with prime order $|G| = 109$ Alice creates a public key ...
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Checking availability of Unlimited Strength cryptography programatically [closed]

Is there a way in Java that I can check that the Java Virtual Machine's Cryptography Extension allows the maximum strength of cryptography to be used in the machine's jurisdiction?
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How is the keystream actually generated in AES CTR

I've been trying to find out how the keystream in AES-CTR is generated, but I can't actually figure it out. Wikipedia and any other sites that "explain" it just say the nonce is padded with the ...
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1answer
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Why does decryption fail after modification of the ciphertext for RSA with OAEP padding

I have ciphertext which was encrypted using RSA with "OAEPWithMD5AndMGF1Padding" - i.e. OAEP using MD5 for the Mask Generation Function. I understand the general ...
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CTF RSA Problem [closed]

I am doing a CTF and I came across a challenge I do not know how to solve. We are given a key generator and asked to find a way to factor the keys $N = pq$ it generates. The intended way is to ...
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Why is writing your own encryption discouraged?

Say I want to write an encryption algorithm to communicate between me and my friend for this private use. How is that bad? E.g. I can take the word Hello and ...
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Mac then Encrypt over Encrypt then MAC [duplicate]

Are there advantages between using Mac then Encrypt over Encrypt then MAC?
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Error propagation in CBC [duplicate]

I am doing an error propagation experiment with the CBC mode.I have encrypted a 100 byte text file with openssl. I made the 55th bytes of my encrypted file corrupted.As per theory the corresponding ...
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openssl encryption salt length

when i was reading the latest source code of openssl, i found openssl enc has an 8-byte (64-bit) salt length; because the same ...
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AES CTR - Pause and resume encryption?

I am using AES/CTR/NoPadding to encrypt while downloading files in one of my application. The encryption is done along with downloading. When the internet is not available in the middle of downloading,...
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1answer
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Is there asymmetric encryption in SSH?

I've read in DigitalOcean article about SSH that in order for a server to authenticate a client: The server sends the client this encrypted message. If the client actually has the associated ...
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0answers
864 views

Does encrypting the key with itself make it easier to crack the ciphertext? [duplicate]

As the title states; Is there any risk from encrypting the key with itself? EG. $C = AES(K=K, M=K)$ I'd assume not; after all, how does having the key for a safe inside the safe make it easier to ...
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1answer
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Is there a type of asymmetric and symmetric encryption that's fairly easy to crack?

I'm looking for a type of asymmetric and symmetric encryption that I can crack fairly easily for a school project. I'm looking to compare the difference between asymmetric and symmetric encryption. I ...
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2answers
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Decently safe amount of AES key derivation?

I am encrypting my computer using Veracrypt. The default 500,000 derivations is quite slow, what would a "safe" balance be between security and speed? My password is more than 20 characters.
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CRYPTO WITHOUT THE KEY [closed]

"Y ipkywurfb zkl ckth pjf ofb bfrpkypi hf. Y jifkc iifzzy tc xymw bfemfi pjf fpywgpktcwg trb lbyr. Pjf ztwagrimtwi dfkf tc y amtrfwzf fromkkfp pt ofjtrb. Fafklpjmwu dyi wtmigcwtz. fD pjktwufb ktgwb ...
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How to determine the shift key to decrypt a ciphertext which was encrypted using Caesar cipher?

So I found this question in a model paper, Break ciphertext ”BJJY GPXF DI TJPM ZSYH” which is encrypted by a Caesar Cipher. This gives a meaningful plaintext if we use 21 as the shift key. So ...
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Randomizable encryption scheme [duplicate]

Given an encryption $c$, I want to re-randomize it in such a way that the result is a ciphertext $c'$, which encrypts the same value as $c$, however it looks completely different. In a sense, the ...
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Can we proxy-re-encrypt using homomorphic encryption schemes?

Homomorphic encryption schemes are PKE schemes with an additional special method Evaluate. The Evaluate method takes input any function (as boolean circuit) and encrypted inputs of the function and ...
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How to extract the keyword from a mono-alphabetic substitution cipher

I am a beginner to cryptography and I have the following question. I know that to extract plaintext from a mono-alphabetic substitution cipher I can perform shifting the characters by $n$ times until ...
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1answer
51 views

Is there a way to do anonymous encryption to a recipient?

Is there a way to do anonymous encryption to a recipient's Public key, where the only way to open a message would be to decrypt with your own private key + passphrase?
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1answer
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Encrypting multiple small messages with a single reused symmetric key

What is a good way of doing this? Practical and Secure. This is for a browser environment. For example, let's say there are a few 100 independent messages of about 100 characters each that you want ...
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How strong is XOR encryption of 256 bit plain text with 256 bit key?

I was wondering if we take just 256 bits of plain text and simply XOR every bit with a 256 bit key, how strong can it be ?
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Is the scytale a Block Cipher?

Can we consider the Scytale a block cipher ? If yes why ? Can you tell me ?
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True asymmetric ciphers beside RSA

Is there any TRUE public key cipher beside RSA? Most people would answer Elgamal or ECC, but for what is my understanding (and I know cryptography only superficially), those are not true asymmetric ...
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How to do cryptography without knowing computer science or AI?

I'm interested in ciphers, codes, patterns, and mathematics, but do not have extensive computer programming acumen (VERY basic Java skills). I know nothing about machine learning, AI or anything in ...
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1answer
50 views

Encrypt data. Create 5 keys. Just 3 keys are needed for decryption

I would like to encrypt some data and create 5 keys. These keys are stored in different places. If I want to decrypt the data I just need 3 of these 5 keys. Is there a way to do this?
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1answer
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Security defined with space complexity

My question is about security defined through space complexity. Suppose I have an encryption function $C=E(K,P)$ for which it can be proved (algebraically) that given $P,C,$ the possible keys which ...
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1answer
195 views

Encryption: am I doing it right?

I'm trying to get a per-user encryption key scheme off the ground and need some validation from wiser crypto pros. Consider the following procedure: User provides registration information to include ...
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Can one encrypt a series of computation?

Normally when one speaks of encryption, it refers to encrypting data. Recently, a client requested a proprietary algorithm be executed on the client-side, in public web browsers. The input data would ...
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1answer
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What is the difference between PKCS1 v1.5 and PKCS7? Is PKCS7 a superset of specifications in PKCS1 1.5?

I have a requirement wherein we have to verify the PE binaries generated for an aarch64 platform. These binaries are then signed using the opensource sbsign tool ...
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1answer
79 views

Simple block cipher

I came up with this concept, which I thought would be pretty secure. So the idea is this, you have a message $M$, which you split up in blocks of each 256 bits. You generate a random (pseudo-random ...
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2answers
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Books about stream ciphers

I am new to ciphers and for my assignment i have to implement a stream cipher algorithm without libraries (on my own). So my question is: Does anyone know about any GOOD books which have examples and ...
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1answer
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2DES and 3DES against a DES build with complimentary

I saw this complicated question and I am not really sure about it, would appreciate your view on it. Is the following build stronger than 2DES or 3DES with 2 different keys (or even normal DES)? $...
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Are there any web puzzles I can solve without programming knowledge?

I don't know much about computer programming (taking an Intro to Computer Programming course at school), but discovered Cicada 3301 and was hoping there is something similar I might pursue for my own ...
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1answer
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Why use PBKDF2 over SHA-512 to derive AES encryption key? [duplicate]

Suppose I am using user passwords to derive AES-128-CBC encryption key. This key will be used to encrypt some sensitive data for the user so that even the website owner / operator can not decrypt it. ...
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Why should I use Authenticated Encryption instead of just encryption?

There are various different modes of operation for block cipher use, some of which provide "encryption" and some of which provide authenticated encryption. Why should I use an authenticated ...
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ZKP: Asymmetric encryption with confidential message and known hash

I'm searching for a ZKP package that supports asymmetric encryption so I can implement the following scenario: Carol encrypts message $m$ with Alice's public key and sends the ciphertext to Alice. ...
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Why doesn't WhatsApp encryption multiply file size [duplicate]

WhatsApp uses and end-to-end encryption, on both personal and group chats. According to my understanding, that means every message I send to a group is encrypted on my Device for every group member ...
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How to perform ByteSub transformation? [duplicate]

Can anybody please tell me how do we perform ByteSub transformation of AES to 01001001.
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How to show that Affine crypto have a valid decryption

I just need to know how to attack a question I have in my textbook this is like: Let $E_1 (x) \equiv 17x + 7 \pmod{28}$ and $E_2(x) \equiv 23x + 11 \pmod{28}$ be encryption functions for two ...
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1answer
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Generate private key from public key RSA

I am doing a tutorial where my lecturer (PhD) gave me an optional question to do relating to RSA. He said: write a python function that takes as input the server’s public key and then uses that to ...
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What encryption should I use: Blowfish, Twofish, or Threefish?

The title of this thread pretty much sums up what I'm asking: what is the best encryption to use out of the three — Blowfish, Twofish, or Threefish?
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What is the likely cause the RSA algorithm gives back plain text in this case?

Text book question of Chapter 9 of "Crypto and Network Security" by William Stallings: When using the RSA Algorithm — if a small number of repeated encodings give back the plain text, what is the ...
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Is a keyed MAC sufficient for integrity protection?

I'm working with the above figure which shows a challenge-response protocol. ...
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1answer
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Why do we use prime numbers apart from hard factorization?

Why are prime numbers important in cryptographic constructs? I am not interested in RSA examples where factorization is the hard problem itself, that makes sense. However wherever I go I encounter ...
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1answer
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Difference between Key Scheduling and Key Generation?

I am a little bit confused in the terms i.e Key Scheduling and Key Generation. What is the actual difference between these two terms? According to Wikipedia, the terms are described as: Key ...