Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

3
votes
1answer
126 views

Can quantum computers break quantum cryptography?

I happened to learn that encryption by quantum cryptography would be impossible to break as it's state changes the instant of an eavesdropping event(by non-quantum systems) occurs. But I'm not sure if ...
2
votes
2answers
90 views

Two working decipher keys giving various, valid results for one ciphered message - is it possible?

Let's assume following scenario: There's a ciphered message. Two decipher keys (let's name them A and B) are known. Message deciphered with key A gives valid result - normal text but with no secret ...
1
vote
2answers
55 views

Whatsapp E2EE - Why scanning the QR-code?

E2EE can be established in Whatsapp by scanning the QR-code on the other person’s phone. But I read on the FAQ page that this code / number can also be sent to the other person via SMS, Email, etc. ...
3
votes
1answer
67 views

Basic Vigenere Cipher

I'm taking my first cryptography course and having trouble deciphering some Vigenere encrypted text. I was able to crack the first one: I'm having difficulty with the other two. I think the ...
1
vote
1answer
147 views

how to compute the correlation between two binary vectors?

We find different equations to compute the correlation or correlation coefficient: $\begin{align*} corr &= \frac{a+d}{a+b+c+d}\\ &= \frac{(a+d) - (b+d)}{a+b+c+d}\\ &= \frac{(a+...
1
vote
1answer
64 views

Why use a date-dependent substring of a pre-shared key instead of just the key?

I've recently come across a situation where one system passes an encrypted payload to another system. The payload is encrypted using a pre-shared key. However, instead of just using the key itself, a ...
-1
votes
1answer
40 views

Question About ECC Primitives (GnuPG)

In version 2.1, GnuPG featured primitives that use elliptic curves. For encryption, one option was ECDH, which confused me. I thought ECDH was for key agreement, not public key encryption. How does ...
3
votes
1answer
57 views

stream cipher and block one, which one is faster to encrypt/decrypt?

As the title says, I would like to know which one is faster. I read in some book it indicates the stream is faster since it encrypts one bit at a time; the others show block is faster since it is ...
2
votes
1answer
66 views

AES ECB mode for both encryption and authentication

Can AES ECB mode be used for both encryption and authentication, assuming the following conditions are always true? Encryption of exactly 128-bit (1 block) size messages Different keys used for both ...
-1
votes
1answer
66 views

Is this problem still as hard as discrete logarithm (modified ElGamal)?

I am trying to find a vulnerability or proof for the following problem: ElGamal part. Given $g\in\mathbb Z_p$ where $g$ generates $\mathbb Z_p^\star$, select randomly $k\in\mathbb Z_p$ and calculate ...
2
votes
2answers
163 views

Differences between hash- and encryption algorithms?

There is a lot of confusion between hash- and encryption algorithms; I would like to understand: When do we use a hash algorithm and when do we use an encryption algorithm (a cipher)? How difficult ...
1
vote
1answer
39 views

How can process algebra help to design security protocols?

Would you please tell me how process algebra could help me to design security protocols? More specifically, can I use it for proving the security of protocols? Is process algebra used for any ...
1
vote
0answers
64 views

Need help decyphering message [closed]

THEIR DIFFERENCE WILL REMAIN, LONG AFTER THEY ARE DEAD Dear Friend, IV IV 12 8 14 - 19 14 18 9 13 IV I C C 9 17 IV 17 12 IV 8 14 IV 7 F 14 IV 7 19 D IV 12 15 F 19 E IV 8 17 IV 7 12 15 F 19 13 17 9 E ...
-1
votes
1answer
110 views

What is Quantum Cryptography?

When it comes to exchanging secure information over an insecure channel, this approach is considered. It all depends on the nature of photons in which third polarization is focused. It can easily be ...
2
votes
1answer
479 views

Encrypted String length in c#

I am using AES encryption in my application. I used 3 types of encryption AES-128,AES-192, AES-256 keysize. When I encrypt with different keysize(128 or 192 or 256) with the same text, the encrypted ...
4
votes
1answer
466 views

The role of Shift Register Cascades in Cryptography?

Clearly, there are stages when binary bits are needed and this can be done with the help of Linear Feedback Shift Registers. Registers are required to be connected in such a manner that one register ...
1
vote
0answers
92 views

how to compute Bit Independent Criteria on a 4-bit S-box?

The idea of Bit Independence Criterion (BIC ) was introduced by Webster and Tavares . For a given set of avalanche vectors generated by complementing a single plaintext bit, all avalanche variables ...
2
votes
2answers
114 views

Cannot understand Block Cipher example

I learned modern block cipher and saw this example. How many padding bits must be added to a message of 100 characters if 8-bit ASCII is used for encoding and the block cipher accepts blocks of ...
10
votes
2answers
2k views

Can quantum computers put computer security in jeopardy?

There are many articles about quantum computers describing how powerful they are in computing and that they can solve very complicated equations in a short time. One of the biggest security measures ...
1
vote
1answer
28 views

Need literature or link to family of cryptographic invertible polynomials which has distribution similar to inverted bell curve

Please help me identify a family of polynomials P(x,k) with the following properties: $x\in Z_{2^n} $ $\forall k, \forall p_k\in P,\ \exists\ p_k^{-1} |\ p_k^{-1}(...
0
votes
1answer
78 views

Where should I start to learn cryptography? [duplicate]

I want to learn cryptography. I just wanted to ask people who experienced about the field that where should I start? Any recommendation would be something for me. Thank you in advance.
0
votes
1answer
42 views

Is function Deterministic or Probabilistic in the malicious security definition?

As you see, according to the attached definitions from "Efficient Secure Two-Party Protocols", the definition of the security in the semi-honest world has two cases for $f=(f_1,f_2)$.(deterministic ...
2
votes
1answer
111 views

autokey script gone wrong!

I tried to make a script to encode a txt with the autokey cipher. From my poor understanding of the cipher I created another cipher which has nothing to do with autokey: first I encoded a txt with a ...
3
votes
1answer
83 views

How can I get the message which was encrypted before (when decrypting a product cipher) ?

I want to make a product cipher containing s box and p box. where message $m = \{m_1, m_2, m_3, m_4\}$ where $m_i \in \{0, 1, \dots 25\}$ for $i=1,2,3,4$. p-box: $P(x_1, x_2, x_3, x_4) = (x_1, x_3, ...
3
votes
2answers
204 views

understanding the block bits for DES

I'm trying to understand cryptographic protocols, and I've started with the DES algorithm. DES specs: it uses 64 bits for the plaintext, 56 bits for the key, with a result of the same 64 bits of ...
3
votes
1answer
49 views

Does it make sense to have long SSH Key with shorter Passphrase?

If we encrypt our data with a longer SSH key which is protected by a shorter passphrase (with a decent entropy), then the limiting factor is entropy of the passphrase. So why do we use a longer key at ...
0
votes
1answer
36 views

IV transmission from Transmitter to Receiver side in CTR mode for every call

I am using block cipher mode (CTR Mode) for the transmission of voice data. Need to know, how can I transfer the same IV at the decryption side (for every call) as the IV for the same packets on ...
-1
votes
1answer
45 views

what is the impact of smaller bit size sbox

There are multiple S-boxes type, as DES uses 4 bit S-box and AES uses 8 bit S-box. I want to know how this effect the security?? If we use 4 bit or 8 bit. apart from the DC attack. Both provides ...
1
vote
1answer
38 views

what can attackers do between two end hosts

I have one question that I couldn't come up with a nice solution. So let's have this analogy, I have a box full of money and I want to deliver to this my friend. Here if we think of a potential ...
14
votes
2answers
3k views

Calculate all possible keys for AES 128 encryption to exploit hardware encryption

Some background: I am using the MicroChip ATAES132a for hardware encryption/decryption. The ATAES132a is very configurable and can be misconfigured in such a way that the encryption/decryption will be ...
1
vote
2answers
107 views

How is a ciphertext encrypted using random numbers decrypted using a symmetric key algorithm

We use true random number generators as a source of keys for encryption. What I can not wrap my head around is: How is this cipher text decrypted in case of symmetric key algorithm as we need the same ...
1
vote
1answer
224 views

How secure is a 128 bit ideal substitution cipher

A 128 bit ideal substitution block cipher substitutes 128 bit blocks with randomly assigned 128 bit blocks using a key table. How secure is this type of algorithm? Is this practical? Thanks!
-2
votes
2answers
147 views

VeraCrypt a weak point [closed]

Biggest flaw in VeraCrypt(or other Encryption programs) is Hash Algorithm. VeraCrypt hashes (SHA,Whirlpool,Streebog) it is the only point where can break an encrypted disk. Because break algorithm (...
1
vote
1answer
80 views

Hardware, Handheld Password Manager

I am currently working on a hardware project that will utilize the native USB and keyboard emulation capabilities of the Teensy device. Essentially, the user will store an encrypted password database ...
2
votes
1answer
193 views

Use AES in CTR mode with pycrypto

The doc of pycrypto gives an example of using AES in CTR mode: ...
2
votes
1answer
43 views

Encrypting the relationship between two database tables

I'm not a cryptography expert myself, and know enough to know that I shouldn't design my own crypto schemes, so I thought I'd seek advice here. In an application, let's say we have two database ...
5
votes
1answer
124 views

“Power of one” as input to functions of a cryptosystem

What does $1^\lambda$ mean when you pass it as a parameter to the functions of a cryptosystem. The cryptosystem in question is this and a picture reference is this. I have been told it signifies the ...
6
votes
4answers
2k views

Using a blockchain for secure communication

I've recently heard of the idea of using a blockchain for secure communication. No details were given so it's a little hard for me to say that it can't be done. But as far as I know: Secure ...
4
votes
2answers
125 views

How to beat a substitution cipher when adding a pseudo-random number stream?

From view-source:https://web.archive.org/web/19990224060310if_/http://www.cl.cam.ac.uk:80/PGP/pgpdoc1/pgpdoc1_29.html: When I was in college in the early ...
1
vote
0answers
38 views

Turn a homomorphic encryption scheme into one that doesn't have the homomorphic property

Homomorphic encryption is a form of encryption that allows computation on cipher-texts, generating an encrypted result which, when decrypted, matches the result of the operations as if they had been ...
4
votes
1answer
87 views

How can one turn a malleable encryption to not malleable

An encryption algorithm is "malleable" if it is possible to transform a ciphertext into another ciphertext which decrypts to a related plaintext. That is, given an encryption of a plaintext m, it is ...
1
vote
1answer
52 views

Is this problem same as discrete logarithm?

Given $g,h\in\mathbb Z_p$ where $g$ generates $\mathbb Z_p^\star$ Discrete logarithm problem is to find $z$ such that $g^z\equiv h\bmod p$ holds. Take the problem given $g,g',h$ where $g^z\equiv h\...
0
votes
1answer
120 views

When do I need to use hybrid cryptography?

I need to provide confidentiality for a protocol. The protocol message size is between 100 bytes to 500 bytes. Do I need to use asymmetric encryption or hybrid cryptography?
1
vote
1answer
70 views

Perfect secrecy theorem

Let $E = (E,D)$ be a Shannon cipher defined over $(K,M, C)$. Consider a probabilistic experiment in which $k$ is a random variable uniformly distributed over $K$. Then $E$ is perfectly secure if and ...
4
votes
1answer
1k views

Which cipher text is easiest to guess the plaintext?

I know that there are approximately 2^88 diff erent permutations of 26 characters. The stream cipher A5/1, which generates a binary keystream using three irregularly clocked LFSR, and has a 64-bit key....
-3
votes
3answers
234 views

Practical perfect security in bitwise XOR vs integer addition/subtraction cipher

XOR already provides perfect security in theory but it's hard to apply it in practice due to strict requirements. I was thinking about whether simple addition/subtraction in integer format would not ...
1
vote
0answers
34 views

Example of an attack on a message exchange which uses the homomorphic property

Can someone give me an example of an attack on a message exchange using this encryption scheme, that uses the homomorphic property? In my opinion, Existential forgery under directed message attack ...
-4
votes
1answer
78 views

Triple Data Encryption Standard [closed]

Based on this, it looks like something slightly wrong. What would need to be adjusted at the transmitter side to allow the receiver to decrypt the message/data?
1
vote
2answers
48 views

How to provide partial confidentiality and full integrity for a protocol message?

I want to provide confidentiality and integrity for a protocol. I don't want to encrypt the entire protocol message. I do not want to encrypt the header and timestamp of the protocol message, but I ...
0
votes
1answer
60 views

How do i manage encryption keys with a cloud provider?

I would like to provision services from a Software as a Service (SaaS) provider. This is multitenant environment (multiple companies will be using a single instance of the application, with a single ...