All Questions

0
votes
2answers
54 views

SIDH cryptosystem question

I'm trying to understand the SIDH cryptosystem and got confused at this point: Alice fixes base $\{P_A,Q_A\}$ so that it generates $E_0[l_A^{e_A}]$. Then she chooses secret parameters $m_A,n_A$ and ...
3
votes
2answers
78 views

What are linear and non-linear elements in cryptography?

I was reading this answer, How secure is XOR for encryption, and it stated that XOR's aren't good for securing messages as they are linear in Nature. And therefore should be paired with some non-...
0
votes
0answers
21 views

Difference between RSA & ECC [duplicate]

My question is regarding Asymmetric-key encryption, in which situation is better to use RSA? What are the advantages of RSA comparison with ECC but from a security point of view? Thank you
15
votes
5answers
4k views

Is the decompression of compressed and encrypted data without decryption also theoretically impossible?

We have two communication points in an information system, call them A(lice) and B(ackup). B has to store encrypted data received from A. The storage of B is encrypted, but not compressed1. B should ...
1
vote
1answer
96 views

Could time lock encryption be implemented through indistinguishable obfuscation?

In the paper "How to build time-lock encryption", the authors give a theoretical solution to build time-lock encryption using multi-linear based witness encryption and blockchain. However, an ...
1
vote
2answers
53 views

Efficient attack on RSA with known padding scheme and public key

I am having some trouble with an assignment problem. I hope I can get some guidance here. The question provides us with a public key, $N$ and the padding scheme. This is the padding scheme "Assume ...
1
vote
1answer
40 views

NIST elliptic curves behaving anamolous in OPENSSL benchmark

I tried to collect some benchmarks on NIST elliptic curves using charm library. The charm library is just a wrapper over OPENSSL. I experimented with prime192v1 (P-192), secp224r1 (P-224), prime256v1 (...
0
votes
1answer
34 views

Naming convention for NIST elliptic curves in OPENSSL

NIST standardized 5 elliptic curves (P-192, P-224, P-256, P-384, P-521) for prime fields. When I looked into openssl, these curves are named as prime192v1, secp224r1, prime256v1, secp384r1, secp521r1. ...
3
votes
1answer
170 views

What information does $g^x$ reveal about $x$?

Let $p$ be a large prime number. Let $G$ be a subgroup of $\mathbb{Z}_p^*$ with order $q$ - again a large prime. Let $g$ be a generator of $G$. Consider the following standard protocol for ...
0
votes
0answers
32 views

Strong and Practical Hand Ciphers [duplicate]

I know monoalphabetic ciphers are weak, but my message recipient doesn't like taking the time for the decryption process. I've tried Vigenere, Gronsfeld, Beaufort and Digraphic Ciphers, but he doesn't ...
2
votes
2answers
62 views

Distinguishing Original VS Fake Products

Let's assume that we want to distinguish original vs fake products when a customer receives them. I was thinking about using a protocol similar to digital signature. My question is can this problem ...
0
votes
0answers
33 views

How “Resending Message Attack” works?

In the second chapter of Bruce Schneier's book Applied Cryptography, 2nd Edition, 1996, we find this in section 2.7.1 Resending the Message as a Receipt: ...
0
votes
0answers
4 views

AWS cloudHSM ECDSA-SHA256 signature output to DER [migrated]

I am attempting to use an AWS cloudHSM to sign a message that needs to be converted to DER to be verified by another application. The output signature file from AWS is binary and I am struggling to ...
2
votes
1answer
59 views

Where can I find test vectors for the present cipher with a 128-bit key?

Where can I find the test vectors for the present block cipher with a 128-bit key?
6
votes
1answer
2k views

Cryptography and patents

First of all, I've seen a question marked as off topic because OP doesn't cover any issue related to cryptographic work, but the legal aspects, but I'm unsure where to attend to ask the following ...
1
vote
0answers
36 views

From 2-round key-exchange protocol to a public-key encryption scheme CPA-secure

I have to solve this exercise and I really could use some help: Show that any 2-round key-exchange protocol (that is, where each party sends a single message) satisfying $Definition$ $9.1$ can be ...
0
votes
0answers
62 views

How to prove that a predicate is not hard-core?

How can I prove that given a predicate $hc$ and a one-way function $f$ that $hc$ is not hard-core? I was thinking about something like that: i define $f(x) = (g(x), hc(x))$ that is one-way but $hc$ ...
3
votes
1answer
25 views

Estimating difficulty of “Memory-Hard Proof-of-Work” based on “size of memory”?

In Bitcoin proof-of-work, the difficulty of Proof-of-Work is estimated and calculated based on total hashing power of the participants. If total hashing power of the participants is higher, then PoW ...
1
vote
0answers
18 views

Looking for commutative asymmetric cipher for data matching

I need some crypto operation for matching data privately between two peers (let say Alice and Bob). Alice should be able to encrypt her data with Alice and Bob public keys and pass the cipher text to ...
2
votes
0answers
22 views

Test Vectors for XEdDSA

Anyone aware of test vectors (preferably with intermediate values) for the XEdDSA algorithm?
5
votes
0answers
35 views

Finding the period of a function with a single output qubit - impact on RSA

In this paper,May and Schlieper claim that one can find the period of a function $f()$ by embedding $h \circ f = h(f(x))$ for input $x$. This would have the immediate consequence of reducing the ...
4
votes
2answers
124 views

Does ChaCha20/Salsa have the same Bit Strength as AES for identical key sizes?

i.e. does ChaCha20 with a 128bit key, require 2^128 attempts to brute force, as with AES-128, theoretically? Ps. notwithstanding that ChaCha is a stream cipher.
2
votes
1answer
74 views

Symmetric property of DDT of inverse function

Given a bijective function $F: \mathbb{F}_2^n \rightarrow \mathbb{F}_2^n$. The entry of the Difference Distribution Table (DDT) at row $\alpha$ and column $\beta$ is defined as $$DDT_{F}(\alpha,\...
2
votes
1answer
63 views

Is Curve P-384 equal to secp384r1?

I am a bit confused with different notations of elliptic curves. Specifically, I am comparing the NIST specification with the SECG specification. More specifically I want to know if the NIST curve $...
2
votes
1answer
68 views

Shuffling alphabet cipher [on hold]

Disclaimer: this is actually a coding challenge therefore I am expressly not looking for complete solutions. The way the cipher works is as follows: Start with ...
-1
votes
0answers
24 views

RSA - Deterministic Encryption vulnerabilities [duplicate]

Which are the vulnerabilities of RSA algorithm due to the fact that is a deterministic encryption method?
0
votes
0answers
40 views

Signal protocol and VRFs

I have read through the Signal protocol specifications, but I am quite confused about when is the VRF output from VXEdDSA used. What is its application inside the protocol?
0
votes
0answers
25 views

Using Alberti Disks to Create a Strong Cipher

Could one use three different disks set at different positions and encrypt a strong message? For example: Wheel 1: A = J Wheel 2: A = E Wheel 3: A = B First letter is encrypted using 1 and then ...
2
votes
0answers
37 views

Gentry-Halevi’s Fully-Homomorphic Encryption and hermite factor

In section 7.2, page 18 in Chen-Nguyen paper regarding BKZ 2.0, they point out different Hermite factors related to Gentry-Halevi FHE. More precisely, it is said that the critical Hermite factor for ...
1
vote
0answers
61 views

RSA vs. Super Computer vs. Quantum Computer

I know that RSA is known to be secure in the current landscape of computing, and I know that RSA is known to be broken in the world of quantum computing and cryptography. I have two questions, can ...
1
vote
0answers
21 views

How does cartridge protection distinguish an original vs fake cartridge? [migrated]

Based on what explained here, genuine ink cartridges may come with cartridge protection embedded in their chip. Once an ink cartridge is installed, printer will mark it as protected. What is ...
16
votes
1answer
3k views

Is a hash a zero-knowledge proof?

I’m trying to wrap my head around zero knowledge proofs, but I’m having trouble understanding it. In my current understanding, zero-knowledge proofs prove to the recipient that the sender has a ...
2
votes
1answer
67 views

How is SPHINCS Hash-based signature “stateless”?

I really hope someone can help me with these questions related to SPHINCS. I am trying to understand the concept of “stateless” vs. “stateful” signature scheme which is the basis of SPHINCS. I went ...
-1
votes
2answers
39 views

How many different subgroups exist in composite order groups? [on hold]

For a composite order group $G$ of order $N$, s.t. $N = pq$ where $p$ and $q$ are prime numbers. By the Lagrange's theorem, the order of every element should either be $p$ or $q$ or $N$. Every such ...
0
votes
0answers
4 views

IP Encryptor and Firewall [migrated]

Firewalls implement IPsec VPN and perform packet filtering. IP Encryptor, on the other hand implements IPsec VPN and achieve security goals (confidentiality, integrity and authentication). What are ...
8
votes
4answers
195 views

Signature security proof in the Random Oracle model

As a study case, I consider the BLS signature scheme, but the following question is relevant in the general context of security proofs in the Random Oracle model. Let us briefly recall BLS signature ...
0
votes
2answers
38 views

Discrepancy in modular encryption

I'm trying to work through an encryption assignment and the instructions aren't particularly clear because they don't go hand in hand with the lecture video. Using encryption key e = 9 in modulo 23,...
2
votes
1answer
135 views

Blowfish encryption with different keys produces same ciphertext

I have set up a test app with Blowfish encryption taken from someone else's library. I have been astonished to find that password "Test" gives the same encrypted ...
4
votes
0answers
62 views

NTRUencrypt in NIST competition

Why did the NTRUencrypt team not maintain the NTRU1024 release in the NIST second-round competition? Is this because of the speed performance or security performance or other things?
3
votes
1answer
52 views

Shared secret beginning with 0h?

I'm designing a system where my hardware piece uses an ATECC608A to calculate an ECDH shared secret in order to exchange data with a HSM in the cloud. For some unknown reason, whenever the first ...
0
votes
0answers
6 views

Can use openssl instead of Python RSA and Base64 algorithms? [migrated]

Can use the openssl command to implement equivalent functionality with Python RSA and Base64 algorithms? For example, the RSA public key and the password to be encrypted are known. The Python ...
1
vote
1answer
76 views

Are Merkle Dags really Dags in most cases?

Let $H$ a cryptographic hash function of image length $n+1$ and $s_0$, $s_1$, ... , $s_k$ a finite sequence of bitstrings (length $>n+1$), such that $s_j$ contains a hash of $s_{j-1}$ for all $1\...
0
votes
0answers
60 views

Does such cryptographic scheme exists?

Is there any multi-key additive homomorphic encryption scheme based on elliptic curve cryptography? Meaning adding encrypted values encrypted with different public keys and decrypt the total sum with ...
0
votes
1answer
34 views

Why create a subkey in the digital signature algorithm

In the signing step, wikipedia, a subkey is created. A key k is randomly chosen from 1..q-1. What's the use of that k? If the k is to make less exposure to the ...
0
votes
1answer
72 views

Entity authentication protocol by encryption

I'm not a cryptography expert, so excuse me if the question seems very trivial. I need to know if this protocol is secure against a MiTM attacks and ensure a safe entity authentication method. We ...
1
vote
0answers
77 views

Security of an Elliptic Curve Public Key with a “Small” x-coordinate

Consider an elliptic curve over a finite field $F_p$ with $p$ prime and order $n$. Let $Q$ be a generator for the field. Given a public key point $P = aQ$, suppose we have an algorithm that finds an ...
1
vote
0answers
45 views

Is there a public-key system that can chain?

Does there exist any asymmetric cryptosystem that has the following properties: If I know somebody's public key PBK_1 and my own key pair (PVK_2,PBK_2), I can construct a new public key PBK_3 such ...
0
votes
1answer
35 views

Key exchange without an underlying semigroup

I am wondering whether there is a general reformulation of perfect forward secrecy for 2 party key exchange in 2 messages using semigroups. I am looking for references, which would discuss such ...
1
vote
1answer
98 views

Does such a cryptographic protocol exist?

Persons A, B and C put x€, y€ and z€ in a pot, respectively. Suppose that anyone can make a withdrawal from the pot as long as they prove they have such a right and that the y€ that B deposited is ...
8
votes
1answer
3k views

How long does it take to crack RSA 1024 with a PC?

Using an Intel Core i5 CPU, how long does it take to crack RSA using a key size of 1024 bit (generated using a secure key pair generation function)? Suppose for instance that we have thousands of ...

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