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.
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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 ...
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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 ...
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What could these blocks of numbers represent? [closed]
The other half of the puzzle is here:
in kinds trees of with forests thickest and the forest overgrown of allnone see to have me have few some wished once never and twiceunexpected your my ...
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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 ...
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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 ...
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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://...
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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 $...
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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 ...
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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 ...
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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 ...
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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, ...
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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,...
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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. ...
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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 ...
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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 (-> ...
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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 ...
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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 ...
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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/...
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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 ...
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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,...
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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 ...
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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 ...
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Where can I find test vector of dragon and grain128?
I don’t know how to find.
Like this picture shows.
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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 ...
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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 ...
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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
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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 ...
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What is the lightest cipher that provides AES like security?
The lightest, or fastest cipher, that is well known and quite secure like AES. Is ChaCha20 a good option? Are there any better alternatives that are faster but still as secure?
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No decryption algorithm for Hummingbird-2?
I stumbled upon hummingbird-2 encryption algorithm when I was looking for a lightweight encryption module that can be used in resorce-restrained environments like Network-on-Chips.
A problem I faced ...
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XChaCha20 vs AES 128 security and speed
Is XChaCha20 with 256 bit key and 192 bit nonce more secure than 128 bit key 128 bit key nonce AES, due to using larger key/nonce sizes? Isn't it supposed to be faster due to being a stream cipher? (...
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Sponge Duplex authenticated encryption with nonce reuse or no nonce
With a Sponge permutation in a Duplex construction for authenticated encryption.
illustration example: ascon; actual interest if relevant: keccak
Suppose there is no associated data and there is no ...
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Skipping first outputs of the stream cipher
I remember reading somewhere that sometimes in some stream ciphers it is necessary to skip the first values they produce. I can't find any information on this right now.
But it seems to make sense. ...
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How to crack sha256 used as streamcipher with known or guessable block
Using SHA-256 as a stream cipher appears to bear cryptographic weaknesses, however, I am not quite sure how to implement them in decryption.
Assume that I have an encryption function using 64-byte ...
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Attack against stream cipher (LFSR with ASCII)
I'm reading Understanding Cryptography by Christof Paar and Jan Pelzl. In chapter 2 (Stream Ciphers) there's a question that goes like this:
Assume we have a stream cipher whose period is quite short....
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What does it mean to break non-invertible stream cipher?
Let's consider for simplicity Middle-Square Weyl Sequence RNG:
https://arxiv.org/pdf/1704.00358.pdf
We can choose there parameter for independent stream generation, we can call it key. Let's consider ...
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How do different types of ciphers relate to each other?
I understand that there are symmetric and asymmetric (public-key) cyphers. The first have the same key used for encryption and decryption, while the second use a public key for encryption and a ...
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What is an output symbol?
I'm reading Understanding Cryptography by Christof Paar and Jan Pelzl. In chapter 2 (Stream Ciphers). There is a section talking about "Bulding Key Streams from PRNGs".
They assume a PRNG ...
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Can you use SHAKE256_XOF with XOR to make a stream cipher?
SHAKE256_XOF is an extendable output function based on SHA3-512. SHAKE256_XOF can be used to create an infinite length bit string with 256-bits of security. For example:
...
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What would be the benefit of using a Stream Cipher which achieves encryption performance of 0.01 cpb using 1 CPU thread?
If such throughput could be achieved what would the benefits for a data center or IoT devices in terms of power saving. Also I was wondering if such speed was possible to be realized by a cipher, ...
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How are keys shared safely for block / stream encryption?
I've picked up a grad level computer security class. I read a brief overview on block and stream encryption. I understand and have used PGP in the past and it make since to share your public key. ...
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TRIVIUM Stream cipher how it works
Hello I am quite new in cryptography so I found Trivium stream cipher can anyone explain in basic language how Trivium cipher works
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Is there a Stream Cipher, with the ability of key reusing and what would be the advantages and applications of this kind of stream cipher?
In the case of a OTP (One Time Pad), if we encrypt two different images with the same key, then two encrypted images will be generated. Then if these two encrypted images are mixed with bitwise xor ⊕, ...
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A friend created a great Stream Cipher. How should he move forward to maybe be compensated for his work?
After rigorous testing, it seems that it can possibly be a NIST-level candidate algorithm.
However, explaining or even finding the right people, experts in cryptography to talk about his invention ...
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Applicability of theoretical attack procedure in actual attack to ChaCha cipher
I was studying the theoretical attacks on ChaCha cipher here (See section 3).
There is one special attack procedure which require key-IV(Initial Vector) pairs. These key-IV pairs are special in the ...
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Using Chaskey as a stream cipher
Chaskey (https://eprint.iacr.org/2014/386.pdf) is a a secure, compact and efficient MAC for embedded systems and has won many benchmarks. It is built using an Even-Mansour block cipher. This block ...
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Is OFB-mode a stream-cipher?
I've seen that OFB is considered as a block cipher mode. But could we consider it also as a family of stream cipher?
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Stream Cipher proof of maximal period length for $n = 2^m$
While reading A course of Mathematical Cryptography by Baumslag et al., I have trouble understanding parts of the proof of Theorem 2.3.3, namely the necessary condition :
Let $n\in\mathbb{N}$ with $n=...
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xChaCha20 Block Keys for Poly1305
So xChaCha20 has a nonce size large enough to safely use a random nonce with the same key. Poly1305 generally uses the first block of the cipher's output to generate its nonce. For xChaCha20 it would ...
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Why are stream ciphers computationally secure?
In case multiple stream ciphers exist, I'm refering to this specific instance in which you generate a key that is just as long as the msg, M, as a function of a nonce and a smaller key K.
My textbook ...
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Does Wikipedia's WEP - RC4 example really demonstrate a related key attack or just an IV reuse attack?
On Wikipedia's Related Key attacks page, there is a section about WEP as an example to related key attacks.
Encryption uses the RC4 algorithm, a stream cipher. It is essential that the same key never ...
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