Questions tagged [cryptanalysis]
Analysis of individual security aspects of a cipher or algorithm, not the security of a cipher or algorithm in general (which would lean towards “algorithm-design”).
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Best Known Attacks on Discrete Logarithm in Generic Groups
This is a followup to my recent question Discrete Logarithm Challenges and Records.
I am interested in confirming my understandings from the answer to that question, stated below:
For a discrete ...
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Bit based division property
Bit based division property is a great method of Integral attack on block ciphers, which was invented by Y. Todo.
According to the paper Bit-Based Division Property and Application to Simon Family (in ...
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Is it fatal if a blockcipher uses a sbox with a fixed point at 0?
In a previous question, I asked how to implement arbitrary s-box in side-channel-free fashion. The code I posted in the question loops over all 256 values of a byte to avoid timing channel, and I want ...
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Are Schnorr's algorithm really subject to q-computer attacks?
I was wondering whether quantum-computers really break Schnorr's signature scheme. Schor's algorithm works via the quantum Fourier transform, which reveals the cycle time and thus phi. However, with a ...
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New POST heaviest-chain finder without downloading any blocks or trusting a checkpoint?
In a POST consensus mechanism with no starting stake needed, I may have found a way to sync with the correct chain without a.) trusting checkpoinnts or b.) downloading the whole chain (or even part of ...
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Why using linear increasing nonce in DSA in a bad idea?
Suppose we sign and verify messages with a DSA scheme. Before signing the first
message the necessary parameters $(p,q,h,g,x,y)$ are initialized, including the nonce $k$ as an integer between $(1,q-1)$...
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decrypting full ciphertext of (AES CTR/GCM) based on partial knowledge of the cleartext
I have found myself in a position where I need to encrypt multiple objects (vCards) with AES Counter mode or Galois/Counter Mode using the same key. Now here is the problem the structure of the vCard ...
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DH Finding A Public Key from Public key and shared secret
Is there a known feasible method for determining an unknown public key from a Diffie Helman shared secret and the other public/private key pair?
This would be rarely useful, but I am curious if the DH ...
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Tensor and power bases for SIS?
What is there to say about using a power basis or a tensor basis or some combination of them for the RSIS problem in lattice cryptography?
Restricting to dimension 3 for illustration, usually the ...
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Secure ciphersuite from security-wise sub-optimal unkeyed permutation?
Hypothetically,
IF we were to create a SSL/TLS or QUIC ciphersuite from a single (unkeyed) permutation operating in sponge mode to provide hashing and duplex mode to provide AEAD cipher,
AND IF the ...
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Exploit 3DES-CBC with known checksum of plaintext and repeated IV
I came across the following enterprise encryption scheme. I laughed when I first saw it, but I'm not a specialist and I'd like to know how bad it really is.
3DES-CBC
k1=k2=k3 for 3DES
IV for CBC is ...
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Are there "light" versions of cryptographic hash functions?
After tinkering with cryptographic hash functions, I started wondering if they do have counterpart functions that would imitate their cryptographic properties but with a lower level of strength in ...
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Attack on the chosen plain-text RSA
Reading another user's question, a doubt came to me.
Suppose an RSA oracle exists, with which it is possible to interact to encrypt and decrypt some text. The oracle output is not the decrypted text ...
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How can I perform a one-client MITM attack in a Diffie-Hellman key exchange? [closed]
Suppose we have intercepted a public key exchange (via Diffie-Hellman protocol). In addition to the keys A and B, the generator g and the module p are known.
Assuming that it is possible to exchange ...
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Product Cipher with Two Autokey Cipher
I have a cypher text with I know encrypted two times with Autokey Cipher with same lengths of keys. I am following the statistical cryptanalysis in here when it is ciphered with one time with Autokey ...
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Cryptanalysis of ARX Ciphers
Rotational Cryptanalysis of ARX show that rotational probability of an ARX primitive can be computed by $p^q$ where $p$ is rotational probability of modular addition and $q$ is number of modular ...
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Which encryption method support 256 bytes block size?
I am looking at some secret encryption method that apparently uses CBC and a block size of 256 bytes. I can do a chosen-ciphertext-attack. When I modify a single byte in the ciphertext a complete ...
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Rule 30 based block cipher
So I went ahead an wrote this little program. What it does is it takes a password for a seed and generates a (pseudo-random) bit-pattern using rule 30 from cellular automata. It then XORs our input ...
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Stuck on a cryptanalytical research project [closed]
This is not a technical question, but rather it seeks advice on what to do if cryptanalytical research goes wrong.
I've discovered a new attack that works great in theory, but in practice, it fails.
I ...
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RSA : Is there a way to compute phi(n) or N itself if we only know e, d and a ciphertext?
I am trying to solve a problem where private key exponent d, ciphertext c, and public key exponent e (65537) are known.
How can I calculate φ(n) or n itself?
An extended version of the problem would ...
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Confusion+Diffusion comparison table? (e.g. with Avalanche Criterion / SAC)
I'm looking for a general comparison of encryption algorithms in regard to Confusion and Diffusion (as defined by Claude Shannon),
and if possible, specifically for their SAC and BIC quality.
For ...
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Where did the number of initial plaintexts required for impossible cryptanalysis on Mini-AES came from?
I'm implementing impossible differential cryptanalysis on AES and I've started with implementing it on mini-AES to fully understand the process using R.Phan's paper as a reference.
But I don't ...
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Differential trails in differential cryptanalysis
From section 4.4 of this book https://www.ic.unicamp.br/~rdahab/cursos/mo421-mc889/Welcome_files/Stinson-Paterson_CryptographyTheoryAndPractice-CRC%20Press%20%282019%29.pdf
I'm confused on how the ...
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how to build the plaintext structure for impossible differential cryptanaysis on IDEA?
I'm trying to implement impossible differential cryptanalysis on 3.5 round IDEA using Miss in the Middle Attack on IDEA and Khufu paper as a reference and I'm stuck on the first two steps of the ...
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Calculate the key of a Hill-cipher using known plain- and ciphertext
I know I should calculate the multiple inverse of plaintext with ciphertext $\pmod {26}$. However, the problem I have is that the plaintext is a $3 \times 4$ matrix which is not square, so how would I ...
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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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How does AES-CBC encryption achieve non-repeating blocks of ciphertext?
I am very interested in encryption algorithms, especially AES encryption algorithm in symmetric encryption. To this end, I have studied a lot of theoretical knowledge about AES encryption algorithm ...
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Conceal time-based GUIDs with an affine-cipher?
I'd like to create a custom type of sortable GUID by concatenating an 8-byte nanosecond timestamp, 6 random bytes, a 1-byte node number, and a 1-byte counter. But, such a precise timestamp can be used ...
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Chosen-plaintext attact on AES with MixColumns omitted
Jean-Philippe Aumasson' "Serious Cryptography" says: "Without MixColumns, changes in a byte would not affect any other
bytes of the state. A chosen-plaintext attacker could then decrypt ...
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In a PGP like Application , would compress and encrypt leak information
would compress and encrypt on data comromise security for PGP like application, would it be secure for use in Encrypted Messaging?
I have heard its safe for data at rest encryption , i have heard ...
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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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Significance of theoretical weaknesses?
What is the significance of theoretical weaknesses?
Any real life incident where a theoretical weakness was ignored and later it compromised the system? Whats the dividing line between theoretical and ...
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What are the best known cryptanalytic attacks against AES-128 with 9 rounds?
What are the best known cryptanalytic attacks against AES-128 with 9 rounds?
I found many such attacks on AES-192 and AES-256 with 9 rounds, but not for AES-128 with 9 rounds.
Are there any ...
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By using a block cipher multiple times in a row is a 128-bit BC as secure as a 256-bit BC which uses his 128-key only as part of the message?
For given 128-bit numbers $S$ and $E$ we want to find a series of keys $k_i$ with
$$ E = BC(BC(BC(.....BC(S, k_1),k_2) ..k_n)$$
We can either use a 128-Bit blocksize block cipher similar to AES (ECB ...
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How does the security of AES change if we allow multiple uses in a row? How does it change if we limit the key space? And introduce a filter function?
$$f_0 = A$$
$$f_{n+1}=AES(f_n,k_n)$$
$$f_i = B$$
For given 128-bit values $A, B$ we want to find a chain of suitable 128-bit keys $k_1$ to $k_i$.
The total length $i$ is undetermined. Every valid key ...
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Why is the best way to solve LWE (and Cryptographic related Systems) with SVP (approx)?
Community,
I'm new into lattice based cryptography, and I'm interested about the security of cryptography schemata like Kyber and why the focus of solving this problem lead into solving approx. SVP.
...
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Best attack estimates on AES
The wikipedia article on the Advanced Encryption Standard claims an attack against AES-128 with complexity $2^{126.1}$. The NIST call for proposals for post-quantum cryptography (table on page 18) ...
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Security proof of the Schnorr Signature
How Schnorr signature security can be proved for signature forgery, replacement, and Replay attacks?
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Non-uniform plaintext distribution -- AES attack
Are their any attacks on AES (any mode) in which before the attack is mounted, the adversary is aware that the input distribution is non-uniform?
Most of the work assume that the plaintext is ...
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Automated Security Protocol tool that models algebraic operations
Are there any automated security protocol verification tools that model algebraic operations; specifically addition.
I am familiar with AVISPA and Verifpal, and they are both great and user-friendly ...
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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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How the mimc bug from circomlib was safely exploited in practice?
Several years ago, there was an unenforced constraint on verification in the cirmcomlib library : a tool for building projects using ZsNarks. The error allowed to forge cryptographic nullifiers/proofs ...
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How bad exactly are repetitions in the plaintext?
When the last n bytes of the plaintext are themselves suitably random, but predictably repeat m times in the same message - how bad is that? I'm convinced it is detrimental, but I am uncertain how ...
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RSA decryption problem knowing public key and ciphertext [closed]
new member here.
I am taking a course in computer security, and we just got introduced in Cryptography and especially in RSA Algorithm. Although i got the 'basic idea' behind the RSA algorithm and the ...
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Info AES cryptanalysis
I have some doubts regarding AES weakness and AES cryptanalysis. While it is relatively simple to find Cryptanalysis info on previous ciphers, I get confused about understanding various types of ...
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Statistical closeness of distributions and time-unbounded distinguisher
If two ensembles are statistically indistinguishable, we all know that they are also computationally indistinguishable, i.e., for any PPT algorithm, the probability to distinguish them is negligible.
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What is the standard checklist for designing a Key Derivation Function?
What kinds of properties does a KDF need to have in order to be considered secure? What steps should be taken during analysis to test for flaws?
In particular, I mean a KDF that is going to be used as ...
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How to solve this Baby Bleichenbacher Attack?
I am trying to solve this problem from https://toc.cryptobook.us/book.pdf.
I am having trouble with this question :
(Baby Bleichenbacher attack). Consider an RSA public key (n, e), where n is an RSA
...
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How do I know the most efficient image encryption algorithm?
I am familiar with any algorithm that is based on the number of bits in a key (n-bit) and how to restore a key, such as the Discrete Logarithm Problem or Factorization.
When I use any algorithm for ...
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A probable attack for RSA (factorization): how to improve it?
A probable attack for RSA (factorization): how to improve it?
$N=8*G+3$ can be factored if there is a non-trivial negative $k$ such that
$\frac{(N*(9+24*k)-3)}{8}=-6*m^2 $
[to exclude the two trivial ...
