instruction stringlengths 32 27.2k |
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The BSI (Federal Office for Information Security in Germany) has published a paper detailing the requirements of cryptographic modules for certain applications in the energy sector: Key Lifecycle Requirements.
The paper describes the various requirements for hardware security modules but also includes software based cr... |
I just noticed that the FSE 1996 conference paper which defines ISAAC mentions a counter variable cc.
This variable is said to be the reason why ISAAC has a guaranteed minimum cycle length of $2^{40}$.
However, no-one seems to have noticed (until I did just now) that the algorithm does not use the cc variable for anyth... |
Using TR-31 key exchange, how is it possible to use restrictive modes of use, such as V (Verify only)? If Alice were to generate such a key, and send it to Bob, Bob would not be able to generate a MAC for Alice to verify. Can this be solved without leaving the safe bounds of Key Blocks?
To be specific, I am referring t... |
So I'm reading this article where they talk shortly about pseudo random generators where I'm not quite familiar with some of the notation. They call $\lambda$ the security parameter.
"Pseudorandom function (PRF). Let $\mathcal{F}=\left\{F_{\text {sk }}:\{0,1\}^{\ell_1(\lambda)} \rightarrow\{0,1\}^{\ell_2(\lambda)} \mid... |
Suppose, we have a secure PRF $F$. Then can there be a MAC Scheme $I=(Sign, Verify)$ using F such that $I$ is insecure, but I is secure under the restriction that all the queries for MAC challenges are different?
|
I have read many cryptographic papers or articles where I have came across about the software and hardware implementation for the cryptographic algorithms. I want to know how its been done. Is there any need to create a separate software to do this. Why there is a need of using FPGA board for the hardware implementatio... |
I am using a Shamir Secret Sharing implementation in Java and I have the use case,
that I may have to generate more Subkeys of the Secret after I already generated some.
Generating them works, but if I combine the new keys with the old keys I can't recreate the secret.
I am using GF(256) as finite field.
For example:
... |
Any hyperelliptic curve having base field characteristic dividing group order?
A subgroup of order equal to the basefield characteristic, a large prime?
Having hard DLP in that subgroup?
Having pairing?
New elliptic-hyperelliptic cycle anyone?
SNARKs were introduced with QAP "intermediate" language to define com... |
How RSA keys are tested for primality if they are random generated? I imagine this could be time consuming task.
|
I'm looking for an authoritative reference about the history of salts in the context of hash functions. Why is the personalization string in a hash function called a "salt"? Who should be credited with introducing this technique?
So far I have found:
Plenty of speculative folk etymology on the Wikipedia discussion pag... |
As far as I know, the Second World War was won on codes that used obfuscation, not open source. These were also used during the cold war. For general use (not large companies with hundreds of employees who may or not be trustworthy) surely basic encryption that uses secret algorithms is still of use? I have asked this ... |
About the characterizations of Special Soundness, from Staking Sigmas we have that:
''A $\Sigma$-protocol $\Pi=(A,Z,\phi)$ is said to have ${\it special\ soundness}$ if there exists a PPT extractor $\mathcal{E}$, such that given any two transcripts $(x,a,c,z)$ and $(x,a,c',z')$, where $c\ne c'$ and $\phi(x,a,c,z)=\phi(... |
1- Why SHA2 has SHA224, SHA256, SHA384 and SHA512 variants?
2- Can we say SHA512 more secure than SHA256?
3- Symmetric ciphers use at most 2^256 security level and I saw on the internet people saying how impossible to reach that then Why SHA2 has a SHA 512 variant? Do we need 2^512 security level? İsn't it overkill?
4-... |
So Alice is sending a one-way message to Bob. Alice and Bob both, of course, have their own ECDH private keys, as well as each other's public keys.
I am using BouncyCastle 2.2.1 (BC) in this code. It appears (am I wrong?) that Alice and Bob must have the same Derivation and Encoding vectors (dV and eV) to encrypt a giv... |
Section 4.1 of the paper “Nonlinear Diffusion Layers” [Y. Liu, V. Rijmen, G. Leander] defines the nonlinear function $\rho$ over $\mathbb{F}_{2^m}$ as follows: $$\rho : \mathbb{F}_{2^m}^4 \to \mathbb{F}_{2^m}^4 : (x_3, x_2, x_1, x_0) \mapsto (y_3, y_2, y_1, y_0),$$ where $$y_i = x_i \oplus (x_{i + 1} \boxplus x_{i + 2}... |
I've recently implemented & hosted an Oblivious Pseudo-Random Function (OPRF) based on multiparty/oprf i.e. Burns et. al. EC-OPRF as an AWS Lambda function / API, that can be recurrently used providing an ID (or getting a random one assigned). Also did some web searches prior and after, but haven't ran across anything ... |
This was a CTF challenge I was unable to solve, but I thought I may had come close.
We were given two $N$'s $N_1$ and $N_2$ each calculated with $P_1 \times Q_1$ and $P_2 \times Q_2$; however, $P_1 = P_2 + 2$ where $P_2$ was still prime.
$Q_1, P_2, Q_2$ where calculated by what I think was a fairly standard method (usi... |
I'm working with the secp256k1 elliptic curve and have point doubling and point addition formulas for this curve.
If a point is given $Q_x$ and $Q_y$
Qx = 112711660439710606056748659173929673102114977341539408544630613555209775888121
Qy = 25583027980570883691656905877401976406448868254816295069919888960541586679410
pe... |
I was reading this article on Wikipedia, but I don't seem to understand how this holds: $u^\phi \equiv u^0 \mod n$. Can someone explain it to me? Thank you.
Key Generation
Given block size $r$, a public/private key pair is generated as follows:
Choose large primes $p$ and $q$ such that $r \vert (p-1)$,
$\operatorname... |
In 2012 CRIME attack effectively killed TLS compression. Has anything changed since 2012 regarding compression in TLS or have modern browsers sacrificed security over performance?
If browsers now use TLS compression how does it bypass CRIME/BREACH?
|
I came upon the following hash function (pseudo-code):
function customHash(integer:user_input)
{
user_input = user_input modulo 2654435789
user_input = user_input * 2654435789
ret_to_user = user_input >> 32
return ret_to_user
}
The goal of the problem I am trying to solve is:
Find two inputs [i,j] tha... |
I'm developping an Swift app that communicate with a Java legacy backend using AES GCM, my biggest problem is that Java let you use a 8 bytes iv/nonce (and the legacy code is written with 8 bytes nonce). You can't do that in swift, it result in error.
I can't find in javadoc what happen to nonce too short, i guess they... |
Given:
A function $$G: \{0,1\}^{3n} \to \{0,1\}^{6n}$$ which is known to be a secure Pseudorandom Generator (PRG).
A derived function $$G'(x_1 \| x_2) = G_b(x_1\|0^n\|x_2), \text{ where } x_1, x_2 \in \{0,1\}^n.$$
Question:
Can we assert that $G'$ is also a PRG?
Observations:
$G'$'s output maps to a specific subset... |
This is probably obvious, but I cannot find it anywhere, since all textbooks define OWFs for average-case hardness.
Do we known if worst-case one-way permutations exist assuming $\mathbf{P} \neq \mathbf{NP}$? I don't require average-case hardness, it suffices that the function is hard to invert in the worst-case. That ... |
In the paper located at https://eprint.iacr.org/2011/401.pdf, suppose we replace matrix multiplication with bitwise XOR operations in Definition 5.1 to create an LWE degree-k PRF. I'm seeking clarification regarding how this alteration affects the proof outlined in section 5.4, particularly with respect to Theorem 5.10... |
A Merkle Tree OTS scheme such as XMSS pregenerates 2^h keys that are tied to 1 public key
When the 2^h keys run out, does all the 2^h keys get removed/deleted and the device pregenerates another new 2^h keys and the corresponding public key?
|
I was reading the Hybrid Public Key Encryption (HPKE) RFC and I came across this sentence in section 9.4 "All AEADs MUST be IND-CCA2-secure, as is currently true for all AEADs listed in Section 7.3."
My first thought is that AE (Authenticated Encryption) implies IND-CCA2 by definition ("Introduction to Modern Cryptogra... |
I cannot quite understand, if Finished message serves any particular purpose when the server is being authenticated via certificates, or if it there just for "consistency" or "extra protection".
The Finished message is said to provide integrity of the entire handshake and computed keys. But when authenticated via certi... |
Consider a pairing-friendly elliptic curve $E$ over a finite field $\mathbb{F}_q$ with embedding degree $k$. Do you know examples of real-world cryptographic protocols based on pairings $\mathbb{G}_1 \!\times\! \mathbb{G}_2 \to \mathbb{F}_{q^k}^*$ such that the number of additions in $\mathbb{G}_1$ is approximately equ... |
So Grover's algorithm, also known as the quantum search algorithm, can find an entry, with a high probability, in an unstructured database.
Well can't we consider the basis of a lattice problem an unstructured database, and the lattice point we are looking for the entry in that unstructured database? Could Grover's alg... |
How do I solve equations like this
$$(aX \oplus X+b) \bmod M = c$$
If a,b and c are known?
and if i have system of of equation with different b values, is it solvable? I am particularly interested in $M$ being a power of $2.$
|
Consider a Koblitz elliptic curve over a prime field $\mathbb F_p$, with equation $y^2=x^3+b$, prime order $n$ close to (but different from) $p$. This includes secp256k1, secp224k1, secp192k1, secp160k1, and for a toy example $p=241,b=13,n=211$.
Given $(x_P,y_P)$ for $P$ on the curve, classic point doubling formula all... |
When I study a zk-SNARK scheme, the scheme claims to be transparent. Does this mean that this scheme does not require a trusted setup? Furthermore, if a NIZK scheme includes a Common Reference String (CRS), does that scheme still remain transparent?
|
I am studying a little bit about one-way functions from Dr Goyal's notes.
He constructs the following OWF:
Let $D=\Bbb Z_2^{n^3}$ and $R=\Bbb Z_2^{2 n}$. Given $x \in D$, $f$ interprets $x$ as a set $S$ of $n^2$ numbers, each of $n$ bits and uses deterministic PT primality test to find the first two 2 primes in $S$. If... |
I am interested in modular arithmetic with respect to the prime $p = 2^{64}-2^{32}+1$.
Thomas Pornin has some work on constant time implementation of arithmetic in $\mathsf{GF}(p)$ for this prime (the paper does other things as well --- this is the part relevant to my question).
Using montgomery arithmetic, a constant-... |
On a technical forum discussion, an example key of 16 hexadecimal numbers was said to be 2048 bits in length. I do not understand this as each number would be 4 bytes - 32 bits - therefore to me 16 numbers would be 512 bits. I am sure I have misread something so any clarification would really help. This question may be... |
The last paragraph of Section 1 (Introduction) of the paper “On the Relationship between Resilient Boolean Functions and Linear Branch Number of S-boxes” [S. Sarkar, K. Mandal, D. Saha] contains the following text:
For an $n \times n$ S-box $S$, its linear branch number, denoted by $\mathcal{LBN}(S)$, satisfies $\math... |
Many of the presentations at The Third NIST Workshop on Block Cipher Modes of Operation 2023 complain about the lack of key commitment in AES-GCM.
But isn't that one application of "associated data?" For instance, can't one include a hash of the key (or something similar) in the associated data?
|
Difficulties porting code to OpenSSL 3 may raise some doubts on digest signing. Before version 3 came, digest signing was the only way to use ED25519. On version 3, RSA_sign() being deprecated, I tried to re-use ED25519 code with RSA keys. The code is like so:
char *digest; // digest already compute... |
I'm trying to show that the PRG $G$ defined as below is insecure for any binary matrix $A$.
\begin{align}
A&: m\times n& (n < m)\\
s&: n\times 1\\
G&: \{0, 1\}^n\rightarrow\{0, 1\}^{m} \\
&G(s)= (A\cdot s) \bmod{2}
\end{align}
As far as I know, I need to provide an adversary with non-negligible advantage, or prove that... |
Respected community,
I was wondering how weak would AES-128 be, if we provide only a 64 bit key with the other remaining 64 bits either zero bits or public constants, known to the attacker.
Is it easy for the attacker to try $2^{64}$ guesses for the unknown part of the key?
To gain more clarity to my query, lets say I ... |
ChaCha has clear delineations between key, nonce, counter and constants.
What is the reason for not using a XEX-like ($k=0$) approach such that the ChaCha key is 512 bits and all the other things are XOR'ed with the key, and only the key is XOR'ed with the ChaCha permutation output?
ChaCha already has some similarity t... |
I recently came across the theorem about $n$-way nesting. It states that if $\mathcal{E}=(E, D)$ is semantically secure, then $\mathcal{E}$ is secure for $n$-way nesting. I'm trying to prove the specific case of $n=2$. For the encryption $c\leftarrow E(k_1, E(k_0, m))$, the adversary provides $(m_0, m_1)$ to the challe... |
I have been reading about lattice attack on ECDSA when partial bits of nonce are known for amount of signatures, So i went through some source code trying to understand how it works.
First of all, Here are the formulas i know.
pk = d*G
r => (k*G).x mod n
s = (k^-1*(z+r*d)) mod n
k = s^-1*(z+r*d) mod n
d = r^-1*(s*k-z) ... |
As is well known, a sigma protocol can be transformed into a NIZK protocol through a Fiat-Shamir transform.
But can the Sigma protocol be transformed into a signature of knowledge in a similar manner?
Intuitively, it seems possible, but which research studies have directly proven this issue?
|
knowing the coordinates of $R$ on secp256k1 and an integer $s$, how do we validate that $s$ is the slope at the point $Q$ on secp256k1 such that $R=2Q$ ?
|
Context
An unknown modulus N with 8 unknown prime factors $p_1, p_2, p_3, p_4, p_5, p_6, p_7, p_8$
a plaintext $m$ is encrypted with the formula $c = 2^m \mod N$
the only things the attacker know are $c$ and $\sum_{i=1}^{8}(a|p_i)$ for any integer $a$ with $(a|p)$ being the Legendre Symbol of $a$ and $p$
Attempts
Obs... |
This paper[1] defines the simulatability and extractability of the signature of knowledge (SoK).
As is widely known, a secure signature scheme should be both unforgeable and non-malleable. Can we derive unforgeability and non-malleability from extractability? （Intuitively, non-malleability seems like it can be derived ... |
Consider how a cheque-book works: Alice goes to the Bank, and gets some incomplete messages, like Alice would like the Bank to give _____ (or the bearer of this paper) the following: _____. This message is verifiably from the Bank, because it's written on a special paper, however the message is incomplete.
In order to ... |
I am currently leaning about LFSRs.
I was told that a binary LFSR with length m has a form of $s_m=a_0s_0+a_1s_1+\ldots+a_{m-1}s_{m-1}$ are binary numbers.
$a_0\ldots a_{m-1}$ are hidden and we are given the output stream of bits $(01101010\ldots)$
How can I determine the coefficients from the given output stream?
Woul... |
This article explains the role of key blinding in Ascon. Key blinding in Ascon involves XORing the key with the capacity part after the permutation in both the initialization and finalization stages.
Quoting from the paper:
we demonstrate that Ascon without key blinding (i.e., with only using
the key to initialize th... |
We know that A function $f:\Bbb Z_2^n \longrightarrow\Bbb Z_2^m$ is a (strong) one-way function (OWF), if:
$f$ can be computed by a PT algorithm. Equivalently, there exists a PPT algorithm that on input $x$ outputs $f(x)$, for all $x\in \Bbb Z_2^n$.
For all PPT adversaries $A$, there exists a negligible function $\op... |
As suggested by the title, I'm working on an exercise where I'm given a hash function $H$ that takes in an input string $x$. I'm supposed to construct a distinguisher that proves $H$ isn't collision-resistant. I'm given a block cipher $F$, $F^{-1}$ as well. $F$ generates outputs of length $\lambda$. The hash function $... |
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 (permutation state leaks, key leaks).
How is this data asymmetry in any way useful? You cannot encrypt the block of plainte... |
Take secp256r1 as an example, the parameter of the curve is
p = 0xffffffff00000001000000000000000000000000ffffffffffffffffffffffff
a = 0xffffffff00000001000000000000000000000000fffffffffffffffffffffffc
b = 0x5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e27d2604b
G = (0x6b17d1f2e12c4247f8bce6e563a440f277037d81... |
Let $X = \{0, 1\}^n$. Given a PRF $F : X \times X \rightarrow X$, define
$$H(k, x) = F(k,x) \oplus F(k,x \oplus 1^n).$$
I think this is insecure, since $H(k, x) = H(k, \bar{x})$ for all $x \in X$, where the bar notation denotes the bitwise not.
However, I was able to come up with the following innocent-looking proof th... |
I'm designing a hash function which uses a double-tree construction and a compression function $c(s,A,B,C,a)$ ($s$ and $a$ may be omitted when there's only one of them) where
$s$ is a set of three key-dependent 8×8 S-boxes
$A$, $B$, and $C$ are 32-byte blocks; $C$ may be empty, in which case it is omitted
$a$ is 0, 1,... |
I would like to ask a question that arose when reading the proof of lemma 4 on page 10 of this BGV paper:
The assumption is:
And the inequality:
So it seems that
$$ \sum_{j=1}^{n} \parallel c'[j]-(p/q) \cdot c[j] \parallel \cdot \parallel s[j] \parallel \space = \space \parallel [<c',s>]_p \parallel - \space (p/q) \s... |
There are a lot of oblivious transfer algorithm. What is the best? It would be good if it were malicious secure, but that is not necessary, if this make protocol very difficult/slow. This protocol should be not very difficult, but the most important it should be fast and has low communication complexity.
|
Alice：has $x=(x_1，x_2,...x_m)$
Bob: has $(y_1,m_1),...,(y_n,m_n)$
For this, Alice wants to get some message from Bob, but does not want bob to know which one she gets
Bob generate random $a \in Z_q$，$cid_i=H(y_i^b),c_i=AES_{enc}(y_i^b, m_i),\forall i \in n$
Bob send all $(cid_i,c_i)$ to alice
Alice generate random $b... |
The calculation/formula i use in deriving a public key from the private key without importing any module in python3 script involves the following steps:
Define the parameters of the secp256k1 elliptic curve:
p = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F
a = 0
b = 7
Gx = 0x79BE667EF9DCBBAC55A0... |
I'm trying to understand how the safe primes numbers are used in Diffie–Hellman key exchange. According to wiki:
The order of G should have a large prime factor to prevent use of the
Pohlig–Hellman algorithm to obtain a or b. For this reason, a Sophie
Germain prime q is sometimes used to calculate p = 2q + 1, called a... |
As we all know, nonce reuse in AES/GCM can easily be catastrophic.
However, I'm wondering if the same risks are present if an adversary has access to:
Ciphertext and corresponding MAC of one message
Small amount of plaintexts and MACs of different messages
using the same (key, nonce) tuple.
Would this leak part of th... |
A sponge has by definition 'wasted' operations (the part of the state which always remains private but goes through all the ops of the permutation).
In return for that waste you get a MAC at the end - some claim that it's for free for some reason.
But the ops wasted on the hidden state cannot compete with something lik... |
I'm confused about something that makes AES GCM great.
It uses MAC to sign data it encrypts. I also uses nonce.
But lets say I encrypt data in software A. Software A produces a ciphertext and a tag as shown here : https://pycryptodome.readthedocs.io/en/latest/src/cipher/aes.html
But when I want to decrypt the cipherte... |
Full-State Keyed Sponge (aka Donkey Sponge) is when a message is absorbed into the full state of the sponge.
Such an approach to MAC construction is considered secure. 1
However for an AEAD or a stream cipher, exposing the state obviously breaks it.
Would utilizing a XEX-like approach be able to secure such a scheme?
... |
It is well-known that, in the setup phase of Pedersen commitment, it is necessary to generate $g,h\in G$. Then a user can compute $c = g^vh^r$ to commit the value $v$.
Is a trusted center needed to generate $g$ and $h$?
In other words, can $g$ and $h$ be publicly generated?
|
I am trying to implement the RSA cryptography algorithm using C language. I am not sure of the size that each operand should have. Let me explain:
RSA requires to generate two huge prime numbers p and q, and compute their product n = pq.
Let's suppose that we want to use a key size = 2048 bits.
So we generate two 2048-... |
According to wikipedia(markdown is striped below) for Decisional Diffie–Hellman assumption:
the DDH assumption does not hold in the multiplicative group $Z(p)$,
where $p$ is prime. This is because if $g$ is a generator of $Z(p)$, then
the Legendre symbol of $g^a$ reveals if a is even or odd.
For example I have $p=2... |
I am struggling with using Microsoft's BCrypt library in AES-XTS mode.
I've confirmed that the Cipher Block Size is 16 bytes (by getting the BCRYPT_BLOCK_LENGTH property). I'm setting the Data Unit Size to 256 (by setting the key property BCRYPT_MESSAGE_BLOCK_LENGTH); I realize 256 is a bit unconventional, and 512 or 4... |
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 is a fairly expensive process, I am using these bits to seed a CSPRNG which finally provides the user with a stream of ra... |
So I’ve been reading about different ways to store passwords on servers (plain text, encrypted, hashed, hashed + salt, slow hash + salt) and I wanted to find a way where a leak of the stored passwords isn’t an issue without resorting to very slow hashes (since slow hashes means a lot more computer power as people sign ... |
The NTRU key generation involves polynomials and their arithmetic in polynomial rings, which is a bit different from arithmetic in modular integers.
In the NTRU cryptosystem, the public key $h$ is computed as:
$h=g⋅F_q \bmod q \tag{1}\label{r1}$
where $g$ is a chosen polynomial, $F_q$ is the modular inverse of $f$ mo... |
Are there any cryptographically strong hash function and encryption function(s) where hash(encryptA(data)) == encryptB(hash(data)). The functions encryptA() and encryptB() may be identical, or just related.
If no such functions currently exist, are there theoretical reasons (relating to the one-way nature of hash func... |
Are there any two encryption function(s) where encryptB(encryptA(data, keyA), keyB) == encryptA(encryptB(data, keyB), keyA).
The two functions may be related or identical.
The two keys must be distinct and unrelated.
|
Is it possible to use a Distributed Key Generation protocol, like the Pedersen DKG, to generate multiple key sets (one secret key and the corresponding public key) instead of only one, but without modifying the exchanged messages?
|
This might sound like a naive question (And maybe it is (It's an early morning Saturday thought, so there might be some clarity of thought missing)).
Suppose we havea protocol that sends messages as follows:
Encrypt(<Message><Padding*>Hash(<Message>))
*Padding is optional, but if present pads out the message to the ne... |
Is there an encryption scheme where it's hard to guess a valid ciphertext without knowing the key and the scheme is CPA secure?
|
I have an implementation of PBKDF2, which I know
Has two bytes of '=' at the end of the input
Has an input length of 24 (which is a Base64 encoded character representation of 16 bytes of entropy)
Uses one iteration
Has a known 9-character salt.
It's using a SHA1 hasher.
Does knowing the two = bytes at the end of inpu... |
Full-State Keyed Sponge (aka Donkey Sponge) appears to cross over into block cipher mode territory such as Full Block Cipher Feedback Mode:
Full State Keyed Sponge (FKS) construction:
FKS has been shown to be a secure way to obtain a MAC.1
FKS and Full-Block CFB are the same constructs, there apparently even exists a... |
Each Enigma machine setting induces a certain encryption in the sense of a function from the space of plain texts to the set of cipher texts.
The number of different Enigma machine settings can be counted for a given Enigma version (and usage). This is answered here: How many possible Enigma machine settings?.
But do d... |
I came across Prof. Bill Buchanan's video "Lattice Crypto: Ring LWE with Key Exchange" explaining the RLWE-KEX. I understood everything he explained until the last part, where he is talking about removing errors from the shared key using probabilistic encryption.
Alice has the shared key as: $\text{sh} = \mathbf{A \cd... |
Single-key Even-Mansour is secure up to $2^{0.5 \times n}$. Where $n$ is permutation and key size.
Would using $n/2$-key retain same security as $n$-key?
Could the other half be used as a tweak?
|
A lot of cryptography is based on the assumption that ${\sf P} \neq {\sf NP}$.
Is it conceivable to construct a cryptography system based on a class of much harder problems than ${\sf NP}$-problems, namely undecidable problems such as the mortal matrix problem?
|
There is DH key exchange, but it requires an exchange before participants get to the shared secret. If Bob has only published a verifying key VB, is there a scheme where the following can be achieved?
Alice, from Bob's verification key VB and some nonce N, derives an ephemeral encryption key EB for Bob
Bob, from EB, N... |
The AEGIS reference document doesn't specify why the authors chose a slow diffusion process and a one way round transformation.
As you can see the previous state is XORed with AES applied to itself shifted by one (wrapped around). This is not a permutation.
The diffusion is also slow when comparing to the possibilitie... |
A semantically secure encryption scheme can not preserve the length of an encrypted plaintext.
How to prove this? or are there some methods that can be used to obtain such information from a semantic secure ciphertext?
|
I'm trying to understand which benefits can using of extension fields in elliptic curve cryptography bring over prime fields. Popular curves like secp256k1, curve25519, secp384r1 are defined over a prime field. Are there any useful elliptic curves over extension fields and what are their usecases?
|
The solution to the problem of finding the primes $p$ and $q$ that have the following form:
$$
c_1 = (a_1 p + b_1 q)^{e_1} \mod{N} \\
c_2 = (a_2 p + b_2 q)^{e_2} \mod{N}
$$
Given the values of $c_i$, $a_i$, $b_i$, $e_i$ and $N$ where $N = pq$.
Can be found in this writeup online. I follow the solution right up to the v... |
As stated for the question above here's an analogy:
You are a robber looking for a house to rob with two different scenarios that might occur.
1. You have a key that you know belongs to a house and you can use it to let you inside. However, you have no clue for WHICH house it belongs to. At any neighborhood and at any ... |
Could anyone direct me to literature regarding privacy proofs in the MPC setting.
For example, how can one prove the following simple problem:
Suppose a setting with $n$ parties $S_1, \ldots, S_n$ wish to compute an additive sharing of $0$, so $r_i\in S_i$ such that $\sum r_i = 0$.
The parties can be assumed to hold so... |
Respected community,
I am using the OpenSSL API's, especially libcrypto and libssl and I am really depressed, thinking about side channel attacks on my implementation. My target platform is Windows, and I am programming in C and C++ and I am linking the libraries dynamically.
I am doing symmetric encryption of some fil... |
By Shannon's theorem of perfect security, if I give you a ciphertext 'LOUPL', you can do a brute-force attack and then you would find plaintexts like 'HELLO', 'APPLE', 'SPOON', but you can't distinguish the true plaintext from the fake one, unless with a probability in 1 of 23⁵. That's a theoretical information securit... |
The MCOE mode provides a really nice way to implement a nonce-misuse resistant AEAD and is based on an arbitrary tweak block cipher.
A specific requirement of the tweak block cipher is that the data block length is the same size as the tweak.
As I use Skein to perform key derivation and hashing, the Threefish cipher co... |
Consider a slightly modified variant of the Gimli SP-box:
function spbox(s) {
x = s[0];
y = s[1];
z = s[2];
X = x ^ (z << 1) ^ ((x ^ (y | ~z)) << 1);
Y = y ^ x ^ ((y ^ (x | z)) << 1);
Z = z ^ y ^ ((z ^ (x & y)) << 1);
return [Z, Y, X]
}
Here s is an array of three $32$-bit words, ^ is the... |
In RSA, the decryption exponent $d$ is typically calculated as $$d= e^{-1} \bmod{(p-1)(q-1)}$$ or $$d = e^{-1} \bmod \operatorname{lcm}{(p-1, q-1)}$$
where $p$ and $q$ are often randomly selected numbers passing probabilistic primality tests such as Miller-Rabin. Usually, the more rounds of these tests, the more confid... |
Do signal protocol derive One-time prekeys from Signed Prekey with some KDF or are they just randomly generated in the same way as Signed Prekey?
|
I'm a bit lost. I know that ZKBoo can be used for proving $y = C(x)$ for any boolean or arithmetic circuit $C$. However, I'm unsure how to combine several circuits when we want to do more complex proofs.
Suppose we have $X = \mathsf{Hash}(x)$, $Y = \mathsf{Hash}(y)$ and $Z = \mathsf{Hash}(z)$ and a publicly known prim... |
TLS 1.2, if encrypt_then_mac extension is enabled.
Sequence number is used during MAC calculation.
But it's not used during the 'body' encryption.
Here, seq_num is used only when calling MAC() function:
https://www.rfc-editor.org/rfc/rfc7366
Does it mean that if client sends some data twice, an encrypted body will be t... |
In IND-CCA encryption, one way to ensure semantic security is to return an error symbol on malformed ciphertext. Some post-quantum KEM algorithms however doesn't do this - instead, they return a "rejected" key.
I'm not sure of the purpose of this. Is it because quantum random oracle model has subtle difference from cla... |
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