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.
276 questions
9
votes
0answers
484 views
Why does Telegram roll its own crypto?
Telegram recently updated its symmetric-key encryption scheme MTProto, which seems to fix some known vulnerabilities. Nevertheless, I still do not understand why they roll their own crypto. What ...
8
votes
0answers
286 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 ...
7
votes
0answers
1k 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, ...
6
votes
0answers
69 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.
...
5
votes
0answers
199 views
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 ...
5
votes
0answers
266 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.
5
votes
0answers
202 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
votes
0answers
100 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 ...
5
votes
0answers
453 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
votes
0answers
62 views
+50
AES reverse Rijndael key schedule with decryption round keys
I want to get the original encryption key (32 byte) of AES 256 (CBC) implementation.
The implementation has the values of the inversed round keys values hard coded into the decryption function.
I ...
4
votes
0answers
81 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
votes
0answers
182 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 ...
4
votes
0answers
91 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
votes
0answers
114 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
votes
0answers
541 views
How to explain Learning With Errors?
I am trying to understand this concept of Learning With Errors. There does not seem to be a layman explanation of it anywhere. Here I describe layman as someone who understands ML concepts a bit (non ...
4
votes
0answers
182 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
votes
0answers
130 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 ...
4
votes
0answers
81 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 ...
4
votes
0answers
71 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
votes
0answers
66 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
votes
0answers
56 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 ...
4
votes
0answers
140 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, ...
4
votes
0answers
199 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
votes
0answers
226 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 ...
4
votes
0answers
228 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
votes
0answers
67 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 ...
3
votes
0answers
247 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 ...
3
votes
0answers
271 views
Asymmetric vs symmetric encryption
I am a beginner learning about encryption and I would like to ask a few questions, hoping this is the right place to ask, so please bear with me.
We have Alice and multiple clones of Bob. Only Alice ...
3
votes
0answers
52 views
Security aspects of a splitted Pohlig-Hellman system
Given a Polig-Hellman (is that really the name for that?) system with
$$C = M^k \bmod p$$
where $M$ is the message, $C$ is the ciphertext, $k$ is a (secret) key (any integer relatively prime to $p-1$...
3
votes
0answers
1k 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
votes
0answers
87 views
Would using a symmetric list of subkeys in a Feistel cipher make our messages vulnerable to oracle attacks?
Suppose I have a Feistel cipher structure that has $16$ rounds. I come up with $8$ subkeys $k_1,k_2,...,k_8$ to be used for the first $8$ rounds and then assign the rest of the keys so that $k_9=k_8,...
3
votes
0answers
92 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 ...
3
votes
0answers
116 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
votes
0answers
233 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
votes
0answers
403 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 ...
3
votes
0answers
146 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 ...
3
votes
0answers
426 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 ...
2
votes
0answers
29 views
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
votes
0answers
74 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
votes
0answers
66 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
votes
0answers
44 views
Generating sets of unreadable/secure and unique random numbers
In the process of some research I have been doing I stumbled across the following 2 claims on the PokerStars website.
We do record all of the hole cards in all real money hands. This is an
...
2
votes
0answers
68 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 ...
2
votes
0answers
58 views
Is it possible to delegate re-encryption key generation?
In a non-interactive proxy re-encryption scheme, Alice, with the key pair $(pk_a, sk_a)$, needs to issue a re-encryption key $re_{a\rightarrow b}$ once she wants to share her secret message with Bob, ...
2
votes
0answers
68 views
End-To-End encryption for VoIP teleconference applications and many-to-many lag-sensitive applications
There are various protocols that allow you to have privacy-enhanced chat.
Those can be either 2-party chat such as:
OTR
SIGNAL
or multiparty chat such as:
SIGNAL
(n+1)sec
mpOTR
GOTR (2013 spec and ...
2
votes
0answers
37 views
Can we encrypt data that must be decrypted with any private key plus a server generate bits?
I have come up with a scenario to make a secure data. Suppose I have a public encrypted file that anybody can download. But whenever anyone want to decrypt that data they need to get a key from server
...
2
votes
0answers
75 views
P2P Website/Database Encryption Process
Sorry if this doesn't fit the guidelines, but I believe it is a conceptual issue that is not opinion-based and can be reasonably answered in a single authoritative answer (I'm also struggling to find ...
2
votes
0answers
57 views
Asymmetric encryption property required in an authentication protocol
We want to choose an asymmetric encryption scheme for use as follows:
A device holds its private key, with the corresponding public key known and trusted by all.
The device also holds a small $b$-bit ...
2
votes
0answers
155 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 ...
2
votes
0answers
289 views
Seekable cipher, is AES CTR a good solution?
I'd like to create a simple file-cipher, which provides seekable encryption (so I can decrypt any part of the encrypted message, without the need of decrypt from the start).
Here's my current idea: I ...
2
votes
0answers
75 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 ...
