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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questions with no upvoted or accepted answers
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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, ...
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320 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 ...
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444 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 ...
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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.
...
6
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How did the cryptographers of Bletchley Park figured out the chi stream of the Lorenz cipher?
How did the Bletchy Park code breakers figured out the chi stream of the Lorenz cipher, that was obscured in the cipher text, which Britain code breakers eventually decoded. It's written in The ...
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215 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 ...
5
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109 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 ...
5
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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 ...
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307 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.
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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 ...
5
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488 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 kind of keys: RSA public/private, AES ...
4
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46 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 ...
4
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2answers
85 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 ...
4
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124 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 ...
4
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183 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 ...
4
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0answers
134 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 ...
4
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257 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 ...
4
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207 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 ...
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326 views
Alternative way to provision secret in Intel SGX enclave
I have a case where I have multiple clients(non sgx, assumeed safe) and server(sgx based), talking over a network. I wanted to provision shared (per client) key which is used to encrypt and decrypt ...
4
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88 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. ...
4
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69 views
Сryptanalysis of Hill's method
The brutal ciphertext is given. The text volume is more than 6000 characters. It is known that the text is encrypted with a 7x7 matrix. Unknown key and plaintext. Is it possible to crack this code? ...
4
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219 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 ...
4
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233 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 ...
3
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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 ...
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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 ...
3
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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 ...
3
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1answer
125 views
Rapid partial block decryption of compute intensive full encryption
Given a block of data D: Is there a encryption/decryption scheme that would allow me to perform a resource-intensive (compute/time/memory) encryption of the full data set with a key k, but allow for a ...
3
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87 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 ...
3
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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 ...
3
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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 ...
3
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149 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, ...
3
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249 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 ...
3
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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 ...
3
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0answers
123 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 a ...
3
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239 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 ...
3
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0answers
534 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 ...
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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 ...
3
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444 views
Increasing the diffusion of the AES-CBC encryption algorithm in pycrypto for python
When encryption is done using the AES-CBC algorithm, the encryption can be thought of as chaining the cipher texts with the previous ones and an IV. However, if its on CBC mode, we give our cipher ...
3
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1answer
238 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 ...
3
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2answers
261 views
If classical ciphers are used with compressed plaintext, how much does it make frequency analysis attack harder?
Classical ciphers, such as Vigenère cipher, are weak and no longer be used. They can be broken by using frequency analysis, that is a well-known fact.
But, the frequency analysis often depends on the ...
2
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1answer
64 views
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 ...
2
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0answers
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What should the hamming weights be between every iteration of AES?
I have an assignment where I have to print out the hamming weights between every iteration of AES's diffusion steps and I have been getting a maximum weight on every iteration, but I can't seem to ...
2
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0answers
85 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 ...
2
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0answers
61 views
Intuition for Cramer Shoup Encryption Scheme?
I was reading the Cramer Shoup CCA2 secure encryption scheme. The scheme is as follows.
Public key = $(g_1, g_2, c, d, h, hk)$, where $c = g_1^{x_1}g_2^{y_1}$, $d = g_1^{x_2}g_2^{y_2}$, $h = g_1^z$, ...
2
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91 views
Security of an Elliptic Curve Public Key with a “Small” x-coordinate
Consider an elliptic curve over a finite field $F_p$ with $p$ prime and order $n$. Let $Q$ be a generator for the field. Given a public key point $P = aQ$, suppose we have an algorithm that finds an ...
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Is it possible to encrypt a user’s email in a zero-knowledge way and still send them emails?
This is kind of hypothetical, but let’s say I have a web app and I want to store a user’s email for sending notifications to.
Is there any zero-knowledge way to hide their email from ourselves and ...
2
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0answers
98 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 ...
2
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0answers
83 views
How to ensure integrity of encrypted data having hashes only?
Having:
plaintext $P$
a hash function $H$, encryption $E$ with key $k$
$h_p = H(P)$ and $h_{E_P} = H(E_k(P))$
Is there an encryption scheme $E$ or hash algorithm $H$ that allows proving that $h_{...
2
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0answers
61 views
Generating sets of unreadable/secure and unique random numbers
In the process of doing some research, I stumbled across the following two claims on the PokerStars website.
We do record all of the hole cards in all real money hands. This is an
important tool ...
2
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0answers
73 views
Derivable encryption key - BIP0032 parallel
I wish to find an asymmetric encryption algorithm that supports key derivation, BIP0032 style.
Meaning that I have some SEED [PRIV] and I give someone some public data [PUB],
then given new public ...
