Questions tagged [decryption]

In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Only authorized parties can decipher a ciphertext back to plaintext and access the original information.

Filter by
Sorted by
Tagged with
0 votes
0 answers
15 views

AES Decryption - Expand Key/First Roundkey

I am wondering how to use and expand keys during the Decryption. Let’s say we have an initial key (128bits): 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 So we get: w[0] = (61 62 63 64), w[1]=( ...
  • 29
1 vote
0 answers
29 views

'str' object has no attribute 'decode' when decrypt aes [closed]

so i have function to decrypt aes ctr. but when i tried to decrypt, the result i got from plaintext is type bytes. i want to get the result of plaintext using decode, because when i encrypt it, i was ...
0 votes
0 answers
31 views

How can i decipher this substitution cipher? [closed]

For a school project we have been given a txt file with has encrypted with a substitution cipher and I have to decipher the whole file. I dont have the key for any information about the cipher, only ...
  • 1
1 vote
1 answer
105 views

Block cipher decryption

I have a course work for university. The question is: My solution to the question is: P||R = D(K,C) However, in the question it doesn't say we are given R so ...
  • 43
5 votes
4 answers
616 views

Does file size significantly affect brute-force time?

Suppose you have two files encrypted with AES-256. One of the two files is 5MB, the other one is over 1GB. Their passwords are reasonably strong: >12 characters, letters, numbers, upper and lower ...
  • 369
1 vote
1 answer
53 views

How are public and private keys generated and used for encryption and decryption in a lattice based cryptosystem?

I've recently become quite interested in lattice based cryptosystems, and I wish to understand them more deeply. I have only a rudimentary understanding of the shortest vector problem (SVP), and its ...
4 votes
1 answer
147 views

Zero knowledge validation to check if private element is in a set hidden on a central server

I am trying to determine how to apply ZK proofs to the asymmetric scenario below. Say there is a list of 5000 secret elements on a centralized web server. Users are trying to guess what those 5000 ...
  • 43
1 vote
1 answer
120 views

Reversing an XOR encryption/decryption function

I have a help recommended high-school project that I'm stuck with. To basically explain the problem: I have an encryption function that is used as the decryption function and I need to reverse it to ...
  • 13
1 vote
0 answers
53 views

How to factorize RSA modulus while given two Public Exponents and the difference between two Private Exponents?

The RSA modulus is the product of two $2048$-bit primes. And the two Public Exponents are both $16$-bit. I also got the difference between two Private Exponents $\left | d_1-d_2 \right |.$ Is there ...
  • 59
1 vote
1 answer
68 views

value bound of r⋅e for LWE Decryption correctness

For LWE decryption, Someone told me that If we can bound r⋅e by q/4 then we can retrieve M by checking if this is closer to <...
  • 121
1 vote
1 answer
107 views

LWE encryption error

in learning with error encryption scheme (e.g. in Kyber scheme). there are two vectors: $u = r^t A + e_2$ and $v= r^t * pk + e_3 + \lfloor \frac{q}{2}\rceil m$ such that $pk = As +e_1$. my question ...
0 votes
1 answer
81 views

Fastest cipher for use with openssl and x86 (Intel)?

I have a C++ application on Intel x86 using openssl to make a connection to a server. What is the fastest cipher that openssl supports? My implementation is currently using ...
0 votes
1 answer
110 views

Verifying Password Using Argon2

I am trying to develop a Rest API using Kotlin/Spring Boot. The JSON request in it, should have a hashed password that was done using Argon2id. Getting the password hashed was pretty straight forward ...
1 vote
1 answer
114 views

Encryption and decryption for LWE

For https://asecuritysite.com/public/lwe_ring.pdf#page=9 , could anyone explain how the encryption and decryption for LWE work ? When I do more reading on https://summerschool-croatia.cs.ru.nl/2015/...
  • 121
0 votes
0 answers
85 views

How to perform an attack on similar messages?

Suppose I have two messages encrypted by RSA with the same public key (N, e), where: M1 = "Hello " + name1 + message M2 = "Hello " + name2 + message The names and the message is ...
0 votes
1 answer
49 views

Increase encryption key length in Shamir secret sharing

Can Shamir's secret sharing work on any size of key?
1 vote
1 answer
281 views

Aes-Gcm how to perform decryption authentication without plaintext output in C#

I'm mainly trying to verify large file chunks which are encrypted each alone with a different key/salt/nonce for each chunk then appended to the whole file in the end to form 1 file. One thing I ...
  • 23
0 votes
0 answers
46 views

Decryption using multiple keys

0 I have a PHP application which calls third party api with username and password embedded in the XML API call from my side. I would like to encrypt and store the username and password embedded in the ...
  • 1
1 vote
1 answer
261 views

What's the best way to recover an AES-256 key from partial key, ciphertext, plaintext and IV?

So I'm trying to decrypt AES encryption with a 32-byte key. I know the first 7 bytes, and the final 19. I also have the plain text, as well as the IV and the encrypted text. I'm currently running ...
0 votes
0 answers
20 views

How to reverse a CRC-16 from the the entire data? [duplicate]

I am trying to reverse the BLE communications with the Daly BMS (Battery Management System) in order to implement it on my own app. I already reversed almost all reads and therefore started to deal ...
0 votes
2 answers
398 views

How can I reverse a so-called CRC16 from the data?

I am trying to understand a request I reverse engineered which is sent to a Daly BMS over BLE. Those requests change the 'sleep after' in seconds of the BMS: For DDDD seconds: ...
2 votes
1 answer
105 views

Is there a discrete log challenge?

RSA challenge is well-known and it has a wiki page. Is there a discrete log for $\mathbb F_p$ where $p$ is Sophie-Germain prime?
0 votes
0 answers
62 views

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 ...
  • 15
1 vote
0 answers
54 views

Can I decrypt AES-CBC ciphertext if I have the key without IV? [duplicate]

Can I decrypt ciphertext from AES-CBC encryption, if I have the key and ciphertext only?
  • 17
1 vote
1 answer
67 views

What's the probability of cracking this cipher using partial information about the private key obtained from $k$ public keys?

For the following cipher, what is the probability of someone without the private key generating a valid public key, using only information from a list of $k$ public keys previously generated with the ...
1 vote
2 answers
71 views

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 ...
0 votes
0 answers
74 views

RSA / AES issue : Decryption

I perform the following commands because I need to decrypt a file -encryption key file- (which is longer than module): cat key.enc | base64 -d > encryptedrawfile.txt openssl rsautl -decrypt -inkey ...
  • 1
2 votes
3 answers
100 views

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 ...
2 votes
1 answer
59 views

How to share decryption ability to others whose public keys are not used during encryption?

as the title says, for example, A uses B's public key to encrypt a message and sent it to B. In later stages, a new member C joins and B would like to let C be able to see this encrypted message (i.e.,...
  • 69
-2 votes
1 answer
85 views

Let negl1 and negl2 be negligible functions [closed]

can we still consider the second function negligible ? is there any main differences between them?
  • 15
1 vote
1 answer
128 views

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 ...
  • 15
0 votes
1 answer
34 views

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?
  • 15
0 votes
0 answers
94 views

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 ...
  • 15
0 votes
1 answer
57 views

Pseudonymization hashing using public key

I have logs containing sensitive data (mail addresses, usernames etc.) that need not only be made GDPR compliant, but in general be secured as best as possible, so anonymization/hashing would be an ...
  • 103
0 votes
0 answers
123 views

RSA: decrypting short message with a different public key

I am having a hard time understanding what I have come across using RSA-textbook. So I have: e = 3 as an exponent a VERY long public key N of 1991 bits (clearly useless trying to factor) a very short ...
0 votes
2 answers
211 views

Plaintext message equals the encrypted message

P=11 Q=29 Euler=280 e=3 d=187 When i take a message “88” for example; Encrypt: 88^3(mod 319) = 88 Decrypt: 88^187(mod 319) = 88 Why does the encrypted message equals the decrypted message and why does ...
1 vote
1 answer
60 views

Is it possible to calculate the plaintext length of an RC5-32 encrypted ciphertext?

Calculating the RC5 encrypted size of any data is as simple as rounding up the plaintext length to the nearest multiple of 8. What I'm wondering is whether this can be done in the other direction, to ...
5 votes
2 answers
259 views

In multivariate public key cryptography, why can not we use the same public key for both signature and encryption?

In multivariate public key cryptography, why can not we use the same public key for both signature and encryption? I read that for signatures the public polynomial $P:\mathbb{F}^n\rightarrow \mathbb{F}...
1 vote
0 answers
56 views

How to decode "SELF-SHIFT" cipher?

I try to use the function $$C_i=E(M_{2i}, M_{2i+1}) = (M_{2i} + M_{2i+1})\bmod 26.$$ to encode English text. For example, Plaintext: The quick brown fox jumps over the lazy dog. Regrouped Text: TH EQ ...
0 votes
1 answer
1k views

How can I decode a XOR cipher with a string key I know?

I have a text that has been XORed with the key "77U" (I am sure of this as it is a file created by a code I have, so I have seen every entry getting XORed by 77U. However, none of the online ...
  • 3
2 votes
1 answer
95 views

Is multiple encryption using a block cipher mode of operation that use only encryption processes vulnerable to Meet-in-the-middle attacks?

Some block cipher modes of operation use only encryption processes, such as CFB, OFB and CTR. If doing multiple encryptions using them, will these encipherment schemes be vulnerable to Meet-in-the-...
0 votes
1 answer
92 views

Is possible to break the encryption on a password by this encryption? [closed]

I wonder if it is possible to break the encryption on a password by such encryption: Where E is the encryption function that uses a known public key of the server.
  • 13
0 votes
0 answers
58 views

Decrypting a polyalphabetic cipher

I'm currently trying to crack a ciphertext with three rotating substitution ciphers. I've tried dividing the cipher up into three parts and do text frequency analysis since I know the language but no ...
user avatar
0 votes
3 answers
592 views

AES Key vs RSA Key

I am compeletely new to cryptography and recently tried to understand it a bit more thoroughly. My question is: How does the Generation of keys differ in the case of AES and RSA. I understood, that ...
  • 101
1 vote
2 answers
81 views

Use of custom DH parameters for TLS decryption

There are several ways to decrypt TLS e.g. in an enterprise environment. I did not see using "backdoored" DH parameters being mentioned somewhere though according to my understanding it ...
0 votes
1 answer
107 views

Comparing different cipher text all saying the same thing

How can I compare different cipher text? When deciphered, say the same thing. I would like to find out the ciphering method. Any help would be appreciated. Thanks. The primary code needs to be a 8 ...
  • 1
0 votes
0 answers
25 views

Are there any schemes for support time-limited decryption that are not based on P2P or TTP models?

Time-lock encryption is a method to encrypt a message such that it can only be decrypted after a certain deadline has passed. This sounds like time-lock decryption. I was wondering if the inverse with ...
  • 774
0 votes
0 answers
128 views

RSA: is it possible for the cube root attack to fail even if e=3?

I've came across an example where the e value is three but no matter what tool/script I try, I can't decrypt it. I'm wondering if the ciphertext and n is super super large, is it possible to crack it ...
3 votes
2 answers
561 views

RSA: The algorithm aside, how are we turning a string into an int and vice versa?

Let's say that I want to encrypt the file plain.txt. The very first step is actually to turn the contents of that file (lets say it only contains the string "...
1 vote
1 answer
298 views

How to Prove Correct Decryption in ElGamal Cryptosystem

I am working on a project that uses ElGamal cryptography using multiplicative notation. The project is an internet voting implementation that uses the cryptosystem to encrypt the received ballots, re-...

1
2 3 4 5