Questions tagged [stream-cipher]
A stream cipher is an encryption algorithm which encrypts arbitrary length plaintext, using a key. Some stream ciphers generate a keystream from only the key, which is then XOR-combined with the plain text, others feed back plaintext or ciphertext into the algorithm to create the keystream.
547
questions
2
votes
1
answer
55
views
hashes that support a stream structure
This is mostly academic curiosity because I'm interested in communication systems, power requirements, padding costs and time. Generally, hashes occur on blocks, and for this example, I'm just going ...
- 4,950
-2
votes
1
answer
95
views
Why increment counters by 1 in stream ciphers?
What is the security rationale behind incrementing by 1 in stream ciphers like ChaCha20Poly1305—which often only changes one or two bits and is very weak and predictible—versus other methods like ...
- 99
2
votes
0
answers
32
views
Sequences over groups and multiplicative recurrences
Feedback shift registers (FSRs) with nonlinear feedback function produce recurring sequences which satisfy polynomial recurrence relations defined by the feedback function. If the register cells are ...
- 171
0
votes
2
answers
89
views
How can LCG based stream ciphers be broken?
I'm watching Christoph Paar's Introduction to Cryptography lecture series on youtube. In it he describes an example of an insecure stream cipher which uses XOR as the encryption and decryption ...
- 111
0
votes
0
answers
129
views
Is known plaintext on Zipcrypto still possible using BK94 algorithm?
In my recent tests both pkcrack and bkcrack are no longer working, maybe it's my PC.
I have zipped pkcrack.exe and chose compression level as store on both ...
1
vote
1
answer
134
views
Is it impossible to improve plaintext attack on Zip crypto in trade of memory vs plaintext bytes requirement?
BKcrack and BK94 states that a minimum of 12 bytes plaintext is required to perform the attack but that was more than 20 years ago, even Michael Stay's improvement is not utilizing modern resources ...
1
vote
1
answer
144
views
BLAKE3 for Block and Stream ciphers?
When assuming the following idea for ciphers:
For a block cipher, a 4-round balanced Feistel network where the PRF is BLAKE3 and the key schedule is: input key, input key with every odd bit flipped, ...
- 11
0
votes
0
answers
90
views
Exposing the vulnerability of CTR mode of operation
In the CTR mode of operation, the plaintext block is treated as a stream cipher, where each byte of the plaintext gets XOR-ed with each byte of the key (which is generated using a nonce and a counter) ...
- 101
0
votes
1
answer
61
views
If a stream cipher uses a truly random, injective function, can we get rid of epsilon?
Imagine an encryption scheme defined as follows for a fixed $|k|$ and $|m| > |k|$:
$K = \{0, 1\}^{|k|}$
$K' = M = C = \{0, 1\}^{|m|}$
$G: K \rightarrow K'$ is a truly random injective function
$E(...
- 267
1
vote
0
answers
81
views
What is a LFSR?
I was reading "serious Cryptography" by Jean-Philippe Aumasson,and when coming to Feedback Shift Registers,I didn't understand what role Polynomials play in the feedback function, does it ...
- 43
2
votes
1
answer
74
views
Trivium reference bitstreams
I am a beginner in cryptography (on my way to retirement) and have programmed the Trivium algorithm in C++ for practice. To check if the bitstream generated by my program is correct, I am looking for ...
- 21
0
votes
1
answer
60
views
Long term Stream Cipher cipher text with MAC storage
Let's say I have x bytes of data that needs to be encrypted with Stream Ciphers such as AES256-CTR, ChaCha20, Salsa20, XChaCha20, XSalsa20.
I would like to ask, since these ciphers typically requires ...
- 159
0
votes
0
answers
71
views
Achieving sub-block non-malleability
I have a noisy one-way communication channel where data is sent as a series of words of width n bits.
Assume n is a constant roughly in the range of 16...48.
I don't want bit errors in one word to ...
- 101
2
votes
2
answers
199
views
Constant values of ChaCha20
Is it possible to change the constant values of ChaCha20?
and how it will affect the security of the cipher.
- 31
1
vote
0
answers
75
views
Extended-Chacha20
Research paper: "Extended-Chacha20 Stream Cipher With
Enhanced Quarter Round Function"
The initial matrix is 6x6, but what are the exact inputs for each index, in other words, how will you ...
- 31
2
votes
1
answer
122
views
Does combining a stream cipher and block cipher produce any vulnerabilities?
In particular, AES-CBC with Blake2b for HMAC combined with xChacha20-Poly1305.
The scheme is to encrypt with xChacha20-poly1305 first, using a key derived from a high entropy password using argon2id ...
- 21
0
votes
0
answers
73
views
Security of the trivium stream cipher
So I've been trying to implement a Non-Deterministic RBG based on randomness polling from non-hardware sources (nothing novel, just a side-project). Since collecting entropy and further conditioning ...
4
votes
1
answer
146
views
How is the Full-State Keyed duplex useful?
In the Full-State Keyed duplex (sponge construction AEAD), plaintext is absorbed into the entire state of the sponge permutation but only a portion of the output can be used else the scheme breaks (...
- 222
5
votes
1
answer
139
views
Cryptanalysis of the GOC
The GOC (Générateur d'Octets Chiffrants, Ciphering Byte Generator) is a PseudoRandom Generator that was used during the late 20th century for content encryption in pre-internet Videotex terminals, ...
- 144k
1
vote
0
answers
76
views
Is this transposition cipher unbreakable?
Given a password as a seed for a Psuedo Random number generator and Fisher Yates Algorithm to shuffle bytes of a string to random places like Hello World to ...
- 19
3
votes
3
answers
359
views
How big of a threat are *diffusion model* based AIs to cryptographic systems?
The diffusion model, which is used by products like Midjourney and Dall-E, trains AI systems to de-noise (remove added randomness) from data to infer what the original de-noised data is. That would ...
- 1,116
4
votes
2
answers
161
views
Is there a standard for LFSRs to test against for use in a stream cipher?
I am trying to implement a stream cipher that uses an LFSR PRNG. I have found resources online that give good primitive polynomials, but I am struggling to find resources with the initial states as ...
- 101
3
votes
2
answers
1k
views
Encrypting arbitrary large files in AEAD chunks - how to protect against chunk reordering?
I would like to encrypt big files using an authenticated cipher. I am convinced to use approach where file is divided into smaller manageable chunks that fit easily in memory (e.g. 1-10MB size) which ...
- 133
1
vote
1
answer
100
views
What is the name of this kind of cipher? (algorithm and description provided)
I have a cipher algorithm that doesn't seem to be one of the "well known" ones I could find. I expect someone has already come up with this and I just don't know the name. Hoping one of you ...
- 113
1
vote
1
answer
181
views
How does the plausible deniability used by TrueCrypt work mathematically?
I have been unable to find any mathematical explanations on how TrueCrypt's plausible deniability encryption works, when using TC containers.
Would someone be able to provide a mathematical ...
- 139
5
votes
1
answer
200
views
Cryptographically obfuscating IP addresses while preserving locality
In an online community, you sometimes have to ban certain IP addresses or even entire IP ranges due to abuse. You may hire moderators to help you with this, but you might not trust them enough to show ...
- 53
2
votes
1
answer
396
views
Deriving secret keys vs generating and encrypting them
Suppose one has a password manager, based on symmetric cryptography, that requires a master passphrase to be unlocked. Argon2 is used for deriving a secret key from the master passphrase.
I need ...
- 123
0
votes
0
answers
83
views
Is my domain separation in stream cipher and MAC accepted?
I would like to implement domain separation in encryption/decryption along with MAC.
The encryption algorithms consists of XChaCha20,XSalsa20,SM4 From China and MAC algorithms consist of HMAC-SHA512 ...
- 159
1
vote
1
answer
375
views
Age: stream cipher with public key cryptography?
I have some rudimentary cryptography knowledge but am by no means an expert.
I generally understand stream ciphers, such as such as ChaCha20-Poly1305, to be symmetric. I am wondering how age (https://...
1
vote
1
answer
119
views
Size of nonlinear filter sequence to recover LFSR feedback polynomial
Let's suppose that there is a filter generator which based on $n$-size LFSR.
Denote a feedback polynomial as $g(x_1, x_2, \dots, x_n)$ and nonlinear filter function as $f(x_1, x_2, \dots, x_n)$.
Let $...
- 11
6
votes
1
answer
302
views
A modern rotor machine, could it be any safe?
I wonder if a rotor machine similar to enigma can be considered secure by today's standards under four conditions:
A rotor machine which consists of 50 rotors picked out of a set of 100.
A rotor ...
0
votes
1
answer
282
views
How many bits of encryption are enforced in WEP (wired equivalent protocol)
I'm currently taking a computer security module in University and as part of a problem have been asked:
My thought for the question is that no it does not provide 64 bits of security strength. This ...
- 77
2
votes
1
answer
93
views
Cascading Streams From the Same Cipher
Does encrypting plaintext multiple times with the same stream cipher but independent keys increase security? If each key is n-bits, and the cascade uses m-streams, could this be considered mn-bit ...
- 23
7
votes
6
answers
2k
views
why XOR is recommended/Used in every paper I read for encryption and decryption stream cipher?
Stream ciphers use a deceptively simple mechanism: you combine the plaintext data, bit by bit, with “key” bits, using the exclusive or operation.
Why can't I use other opeartions such as NAND, AND, ...
8
votes
1
answer
221
views
AES vs. SHA2 in key-stream generation
A KDF in Counter Mode (e.g., see NIST SP 800-108r1, Section 4.1, similar to HKDF) produces the output as what AES-CTR would do if one replaces AES with SHA2 (or, to be exact, with HMAC).
However, NIST,...
- 138
1
vote
2
answers
108
views
How fast does revealing parity bits leak information?
I've got a scheme where I XOR a secret key value with a public (but random) value, XOR together all the bits of the result, and publish that bit (0 or 1), which is the parity of the result of the XOR. ...
- 111
8
votes
2
answers
3k
views
Is Trivium still secure?
What is the best known attack on the stream cipher Trivium?
And is there is any good reason to not use it?
By googling the good key words, I've found this paper, but I'm not enough expert to judge the ...
- 2,625
-1
votes
1
answer
130
views
Attack on cipher that adds modulo FF output of two LFSRs (LFSR-12 and LFSR-19)
LFSR-12 with poly $x^7+x^2+1$ and LFSR-19 with poly $x^{11}+x^5+1$ are used to produce
8 bit of output each, output is then added together modulo FF
(LFSR-12+LFSR19)mod FF
I know first 8 bytes (-> ...
- 1
2
votes
0
answers
86
views
1st round attack on rc4
I'm trying to implement the 1st round attack on RC4 stream cipher according to Attacks on the RC4 stream cipher. For now I am interested in section 4.2 Attack on other key bytes. It works really fine ...
- 21
3
votes
1
answer
169
views
Is SHAKE hash function seekable when using it as a stream cipher?
I searched a lot for this information in search engines as well as taking a look in the SHAKE reference implementation.
If I decide to use SHAKE as a stream cipher, can I access a specific part of the ...
- 887
0
votes
1
answer
121
views
Can attacker create encryption of message m XOR 1^n given the ciphertext c, in nonce-based counter mode?
The following question is from Stanford cryptography course final exam paper.
Suppose an attacker intercepts a ciphertext $c$ which is the encryption of a message $m\in\{0,1\}^n$ under nonce-based ...
0
votes
1
answer
143
views
Various attacks on cipher-images & tools, especially stream-cipher?
What kind of attack of image encryption that exist out there, especially if the cipherimage was created using secure stream-cipher like Salsa20 (256 key) or ChaCha20 (256 key)?
From https://cr.yp.to/...
- 87
0
votes
1
answer
62
views
Stream Ciphers clarification
I am confused about stream ciphers a little so I just wanted to clarify. We have a key that's lets say 2 bits. I have a message that's 8 bits. I used a pseudorandom generator that would add 6 bits to ...
0
votes
1
answer
106
views
Secure symmetric cryptography for low memory/CPU systems
I am looking for symmetric cryptography algorithms that can be implemented on chips with very few resources (about 256K RAM and 16MHz CPU).
An algorithm that works perfectly in this environment is RC4,...
1
vote
0
answers
142
views
Physical meaning of Negligible and Non-Negligible Functions
I've been itching my head over this for a while despite going through the queries related to the topic. Can someone explain me negligible and non-negligible function in a concise way?
As of my naive ...
3
votes
1
answer
238
views
Streams Ciphers - Linear feedback shift register logic behind design
I’m just seeking a better understanding as to the logic behind design of the A5/1 cipher’s keystream generator. Why are the registers degree chosen in such a fashion (19,22 and 23 bits long ...
-2
votes
1
answer
67
views
Where can I find test vector of dragon and grain128?
I don’t know how to find.
Like this picture shows.
- 1
3
votes
3
answers
7k
views
Is there a security risk to use AES-CBC as stream cipher?
I am building a chat application where I want to encrypt each character while they are typing. I would require a stream cipher for that.
I am planning to use AES-CBC mode with HMAC. Are there any ...
- 257
1
vote
2
answers
68
views
Linear complexity of real and complex sequences
In cryptography output sequences of stream ciphers are binary valued (or more generally finite field valued). However mathematically sequences over real and complex variables can also be generated by ...
- 171
1
vote
1
answer
657
views
Common applications and simple implementations of stream ciphers
I am learning about stream ciphers, which apparently are unpopular. I just want to have a better idea of some basic algorithms that are in use or were in use till recently.
I checked:
the OTP: ...
Mah Neh