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.

586 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
14 votes
0 answers
2k views

Has Telegram security been significantly improved with MTProto 2.0?

Telegram messenger's original encryption scheme, MTProto 1.0, has been shunned by most cryptographers for a number of reasons, like being vulnerable to IND-CCA attack; being unorthodox in general, ...
user avatar
9 votes
0 answers
182 views

Are there any weak nonce-misuse resistant encryption scheme?

Nonce-misuse resistance seems to have two standard notions: The stronger notion: this reveals nothing unless the exact same nonce is used to encrypt the exact same message twice. In this case, the ...
user avatar
  • 43.5k
9 votes
0 answers
125 views

Offline Group Key Agreement - Cross Device Syncing

I have a specific use case I am interested in. I have spent the better part of the night reading research papers. I am beginning to believe what I want is not possible so I wanted to confirm here. ...
user avatar
  • 191
8 votes
0 answers
959 views

Key size, performance, and security tradeoffs for AES GCM / CCM

AES can be used with 128, 192 or 256 bit keys and each one appears to have a performance vs security trade-off (What is the effect of the different AES key lengths?, What are the practical differences ...
user avatar
  • 235
7 votes
0 answers
341 views

Security proof in (Ciphertext-Policy) Attribute-Based Encryption

I am having hard time understanding the security proof in Attribute-Based Encryption, especially in Ciphertext-Policy Attribute-Based Encryption. To do reduction in CP-ABE scheme, how do I check that ...
user avatar
  • 71
6 votes
0 answers
115 views

Is it possible to derive a homomorphic signature from homomorphic encryption

At the moment I am trying to find a practical way to implement a linearly homomorphic signature. Background: "In a homomorphic signature scheme, a user Alice signs some large dataset x using her ...
user avatar
6 votes
0 answers
212 views

Is AES resilient to chosen plaintext with access to related keys (key expansion primitives)?

I'm interested in knowing whether a cryptosystem is broken given access to a few primitives. $\DeclareMathOperator{\KEYEXP}{KEY\_EXP}$ $\DeclareMathOperator{\E}{E}$ Suppose that you have access to an ...
user avatar
  • 61
6 votes
0 answers
291 views

How to make a "zero knowledge" cache/key-value store

I'd like to use a possibly insecure cache for storing expensive-to-calculate sensitive information. My requirements are: If the cache ever gets compromised it should reveal nothing about its ids or ...
user avatar
6 votes
0 answers
239 views

Additive homomorphic encryption scheme without change in operator

I'm looking for an additive homomorphic encryption that the addition operator (+) in its plaintext space be the same as addition operator in its ciphertext space. (Schemes like Paillier do addition in ...
user avatar
6 votes
0 answers
547 views

File Encryption (EFS method)

I'm implementing (for learning purposes) a file encryptor, which uses the following method (from http://en.wikipedia.org/wiki/Encrypting_File_System). I have 3 kinds of keys: RSA public/private, AES, ...
user avatar
5 votes
0 answers
146 views

Why does chacha20 not use bitwise not?

Right now chacha20 and blake use constants in order to eliminate fixpoints. As far as I know however inserting a bitwise not every $n$ rounds should eliminate this ...
user avatar
5 votes
0 answers
90 views

How do encrypted radios perform key exchange?

I'm having difficulty finding documentation for the over-the-air protocols used by encrypted public safety radios. It seems that most systems are based on Project 25, previously known as APCO Project ...
user avatar
  • 399
5 votes
0 answers
308 views

What public-key encryption protocol can use the same key pair as ECDSA?

Assume we wanted to use the same ECDSA public/private key pair (drawn for standard ECC parameters, perhaps P-256) for both its intended use (public-key signature), and for public-key encryption; this ...
user avatar
  • 125k
5 votes
0 answers
423 views

Homomorphic system that allows Hamming distance computation?

How can I work out Hamming distance between two binary vectors securely? I would like to know how I can apply homomorphic techniques here.
user avatar
  • 51
5 votes
0 answers
117 views

search of patterns in key schedules

I am developing a new key schedule, and there is this article (Enhanced Key Expansion for AES-256 by Using Even-Odd Method) where the authors also propose a new algorithm and one of the objectives is ...
user avatar
  • 271
4 votes
0 answers
102 views

Why Block Ciphers

I​ fail to understand what block ciphers can do that stream ciphers cannot. Also aren't they construct able from one another. prg(stream cipher) -> prf -> prp(block cipher) Any practical example ...
user avatar
  • 41
4 votes
0 answers
104 views

About the complexity of a path finding attack for a path encrypted with a block cipher (like AES). How many AES calculations count as secure?

Out of $N = s^3$ total points we pick a starting point $p$ and an end point $q$ with $$p=(p_1, p_2)$$ $$q=(q_1,q_2)$$ $$p_1,q_1 \in [0,s)$$ $$p_2,q_2 \in [0,s^2)$$ We want to find a path in between ...
user avatar
  • 475
4 votes
0 answers
75 views

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. ...
user avatar
4 votes
0 answers
90 views

Security analysis of North Korean block cipher Jipsam1

The cipher is a modification to AES and is described on this website: The only difference between Jipsam1 and AES-256 is the S-box. Whereas in AES the S-box is public and constant, namely $$ \begin{...
user avatar
  • 13.6k
4 votes
0 answers
101 views

Can RSA re-encrypt a message without decrypting it?

The goal of this question is to allow a server/proxy to forward an encrypted message without being able to read it with this procedure being transparent to the original sender and receiver. Assume we ...
user avatar
  • 273
4 votes
2 answers
199 views

Proving the right encrypted message was sent

Total amateur to crypto here but I've searched and searched and am at the extent of my knowledge. I've gone down several avenues to satisfy what I'm looking for but I'm just going to describe what I'd ...
user avatar
4 votes
0 answers
146 views

How sensitive is Tiny Encryption Algorithm (TEA) to the magic numbers?

If I needed to implement an encryption algorithm from memory, chances are I would try to implement: TEA https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm How sensitive is it to the magic ...
user avatar
  • 10.7k
4 votes
0 answers
281 views

Why is this Trivium implementation working bytewise instead of bitwise?

I am currently looking into a Trivium implementation available in the FELICS framework. Parameters of the Trivium stream cipher: Key size: 80 bit IV size: 80 bit State size: 288 bit The Trivium ...
user avatar
  • 41
4 votes
0 answers
151 views

Why are matrices so common in symmetric encryption?

Matrices have been used in symmetric ciphers since the Hill Cipher (before?) all the way up to modern ciphers such as Twofish and AES. I understand matrices can be invertible, therefore making them ...
user avatar
  • 1,015
4 votes
0 answers
329 views

Encrypt using ECDH with two different EC public keys, minimizing payload size

Let's say Alice has the private EC keys $a$ and $b$, with a base point of prime order $G$. Alice computes the corresponding public keys $A = aG$ and $B = bG$, and sends them to Bob. Bob now wants to ...
user avatar
  • 141
4 votes
0 answers
382 views

Alternative way to provision secret in Intel SGX enclave

I have a case where I have multiple clients (non SGX, assumed safe) and server(SGX based), talking over a network. I wanted to provision a shared (per client) key which is used to encrypt and decrypt ...
user avatar
4 votes
0 answers
103 views

Implications of TLS-SRP client with improper N validation?

During development of a client side application of TLS-SRP, i noticed a bug that allows an attacker spoofing as the server to send custom, but non-arbitrary $N$ values, with the client accepting them. ...
user avatar
  • 41
4 votes
0 answers
146 views

How to overcome issues with big ciphers? E.g. with small vs. big Vigenére Ciphers

I understand that bigger ciphers show more recurring patterns and therefore should be easier (or at least faster) to decrypt as you'll have a better statistical analysis, being However, if we use an ...
user avatar
3 votes
0 answers
82 views

Encrypt/Cipher and Decrypt/Decipher a string with a secret

In developing an app I have a simple use case in where I want to encrypt/cipher a string (it could also be a couple of bytes because it's essentially just an IP-Address). On the output I think it ...
user avatar
  • 31
3 votes
1 answer
204 views

perfectly secret with key chosen uniformly

Prove or refute: Every encryption scheme for which the size of the keyspace equals the size of the message space, and for which the key is chosen uniformly from the keyspace, is perfectly secret. My ...
user avatar
  • 41
3 votes
0 answers
115 views

Decrypt the same ciphertext to multiple messages of my choice if I can use any key I want to decrypt

In a modern secure encryption scheme, is it possible(both theoretically and practically) to encrypt a message using a key to get the following ciphertext c = Enc(M1,k1) and later find another key so ...
user avatar
  • 67
3 votes
0 answers
68 views

Can the hash of the ciphertext be derived from the hash of the plaintext

Let $C$ be a symmetric cipher $H$ a hash function. Alice uses $C$ with a key $k$ to encrypt plaintext message $m$ yielding ciphertext $c$. She then calculates the hash of the message $h_m = H(m)$ and ...
user avatar
3 votes
0 answers
118 views

Does varying ChaCha rounds add any security?

This paper introduces 'Freestyle' a randomized, and variable round version of the ChaCha cipher. It uses the concept of hash based halting condition, where a decryption attempt with an incorrect key ...
user avatar
  • 1,423
3 votes
0 answers
565 views

Identifying correct cipher

I am trying to decrypt a text(~900 characters) and I started with the assumption that its a Vigenère cipher as the one of the identifier tool identified it as Vigenère cipher and also the Index of ...
user avatar
3 votes
0 answers
100 views

Is it possible to verify attributes of encrypted content?

Let's say that Alice has this information about her, { "name": "Alice", "age": 25, "eyes": "brown" } which she encrypts with a key pair so that no one access ...
user avatar
3 votes
0 answers
57 views

Does Openssl 1.1.1 library supports sending multiple identities as part of PSK?

Does Openssl 1.1.1 supports sending multiple ticket identities as part of PSK? i have gone through the openssl code and i don't see that openssl supports it. could someone please confirm it if i ...
user avatar
3 votes
0 answers
141 views

Is there a partially homomorphic cryptosystem without an inverse (addition without subtraction, multiplication without division)?

I am learning about partially homomorphic cryptography, and was interested to see if there was a system such that one operation was homomorphic, but its inverse was not. For example, if I have two ...
user avatar
3 votes
0 answers
200 views

How to implement security - authenticity/confidentiality/integrity for 6/14 bits radio messages?

I just took over two radio systems (using 433Mhz) - one communicates with 6 bit messages, one with 14 bit messages. Both have a lots of transmitters and one receiver (and, yes bits not bytes). For ...
user avatar
3 votes
0 answers
115 views

Decryption with negligible error

In chapter 2 of Katz's Introduction to Modern Cryptography there is a formal definition of an encryption scheme. As part of this definition, the decryption algorithm is required to be perfectly ...
user avatar
3 votes
0 answers
101 views

Plaintext DH keys in the message header in the Double Ratchet Algorithm

I've been reading details about the Double Ratchet algorithm, and I wanted some clarification regarding the aspect of the DH public keys going out in the plain in the header of every message. Quoting ...
user avatar
  • 131
3 votes
0 answers
2k views

Cryptography behind the Turing Imitation Key (TIK)

When browsing the internet I found out about this amazing phone. Well, it would be amazing if it was actually obtainable. It's called the Turing Phone, and it is supposed to come with as good as ...
user avatar
  • 85.9k
3 votes
0 answers
65 views

What are the practical impacts of Wassenaar Arrangement to crypto development?

Wassenaar Arrangement limits transport of high-grade crypto hardware/software since decades, if I don't err. What are its practical impacts in that direction? In particular, does it hinder in any ...
user avatar
3 votes
0 answers
168 views

Authenticated encryption with Enc-Sign-Mac

I've given a CPA secure private key encryption scheme, an unforgeable private key MAC scheme and an unforgeable public key signature scheme. I want to combine them to protect confidentiality, ...
user avatar
3 votes
0 answers
267 views

How does darkmail (DIME) work to hide email metadata?

While Email encryption can protect the content of an email, the metadata are still readable and can be used to gather important information about the sender and the receiver. There were several news ...
user avatar
  • 181
3 votes
0 answers
98 views

Unknown authenticated encryption mode

I'm running through a protocol specification (LoRaWAN, pdf), and I'm puzzled by the crypto. The data is encrypted and authenticated in the following way: a unique 128-bit key is used; the plaintext ...
user avatar
  • 31
3 votes
0 answers
261 views

How can I design a cryptographically secure, key-dependent s-box?

I would like to design a cryptographically secure, key-dependent s-box, but I am not sure how. Mainly, because I am unsure about the difference in design compared to a random s-box. What is the ...
user avatar
  • 75
3 votes
0 answers
241 views

Explanation of part of a visual cryptography algorithm

I have been working on a project involving visual cryptography and I am stuck with the following problem. My question is related to this paper, AN IMPROVED VISUAL CRYPTOGRAPHY SCHEME FOR SECRET ...
user avatar
3 votes
0 answers
677 views

Avoiding known plaintext attacks with an additional XOR-Layer

Can a cipher that is vulnerable to an known plaintext attack be made secure by adding an additional XOR-encryption? That is: suppose I have an (w.l.o.g. symmetric) encryption algorithm E were the ...
user avatar
  • 265
3 votes
0 answers
155 views

Paper about this secure P2P idea?

Two or three years ago, I was reading something interesting, but then I lost the paper. The paper described building secure and fast P2P networks (not like tor or I2P). Unfortunately, I only remember ...
user avatar
  • 39
3 votes
1 answer
272 views

Why gcd(r,(p-1)/r) needs to be 1 in benaloh cryptosystem

I recently discovered the benaloh cryptosystem. I am working with the system as it is discribed in the following link: https://en.wikipedia.org/wiki/Benaloh_cryptosystem However I need some help in ...
user avatar
  • 173

1
2 3 4 5
12