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Dependence of a Pseudorandom Function's Security on its Input/Output Spaces

Let $n$ be a security parameter and $F:\{0,1\}^{\ell_{key}(n)} \times \{0,1\}^{\ell_{in}(n)} \rightarrow \{0,1\}^{\ell_{out}(n)}$ be a keyed function which forms a family of Pseudorandom Functions (...
0
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1answer
24 views

Are two halves of PBKDF output “related”

In other words, in the context of authenticated encryption using Encrypt-Then-MAC, is this stupid?: ...
0
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0answers
17 views

ECDHE Key with KDF Necessary

Is it necessary to pass a ECDH generated key to a KDF? According to the python cryptography documentation, it is stated that For most applications the shared_key should be passed to a key ...
0
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0answers
25 views

what is the motivation of multipartite secret sharing?

In this thesis chapter 3.1 [1] A multipartite secret sharing scheme is a scheme in which the set of participants is divided into several parts and all participants in the same part play an ...
0
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0answers
27 views

Bitcoin mining nonce and birthday attack

Having read the basics of mining and this about SHA256 (probabilistic?) partial preimage possible? and SAT solving - An alternative to brute force bitcoin mining, I have the following question: ...
-1
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0answers
15 views

Should has the CMAC scheme the ECBC-MAC final block?

As I concerned the raw CBC-MAC scheme is not secure, and to solve this a final block using a different key is used. Also to fix the "Dummy blocks" generation for the padding in the CBC-MAC a CMAC ...
0
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0answers
42 views

collision resistance of a composed hash function

Given a collision-resistant hash function $H(x)$, and I device another hash function by $H'(x)=\sum^{m}_{1}H(x||i) \mod p$. The summation is defined on finite field of prime order $p$. Is the new ...
0
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0answers
3 views

How does windows 10 v.1803 save the password in the SAM file? [migrated]

I'm doing a search on how windows 10 saves hashed passwords in the SAM file. From this article I suppose that Windows does this: If the password is 123456 and the user has RID 000003E9: CALCULATION ...
1
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0answers
20 views

Cascaded XTS vs XTS with cascaded block ciphers

The popular VeraCrypt encryption utility, as well as its precursor TrueCrypt, has the option to cascade multiple ciphers on top of each other, such as AES-Twofish-Serpent. It works by cascading three ...
6
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2answers
2k views

If hash functions append the length, why does length extension attack work?

I have understood that it's trivial to reconstruct the internal state of a hasher for many hash functions, if one only knows the output hash. Then, one can append data after the original data and ...
0
votes
1answer
39 views

It is the IV shared in CBC mode?

I don't know if the IV in CBC mode is equal in both sides of the encryption and decryption operations. I know that the IV must be unpredictable, but has it to be MACed in the encryption side to be ...
2
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0answers
51 views

What security is provided by a certificate? [on hold]

I've been working on the topic of certificates for a little while, and here is what I understand: A certificate is basically a public key + some data about the owner of the certificate + a signature ...
-1
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1answer
65 views

On the security definitions

What are the differences between perfect security information-theoretic security semantic security indistinguishability are there other definitions? Do these security definitions depend on the ...
0
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0answers
35 views

How to encrypt an ASCII word using DES (ECB) [on hold]

I have a word, SIGURNOSTRACUNARSKIHSISTEMA, and my task is to find a value of a second block using initial permutation DES. Since this is more than 64-bit, I need to use ECB, but I have been unable to ...
1
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1answer
46 views

Point doubling with only one coordinate

In many source codes that implement ECDH, there is a function that multiplies the base point of that curve with a constant. This function usually takes as arguments the constant and just one ...
1
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1answer
71 views

How is the PRIVATE KEY actually created in the first place?

How is the "Private Key" created in the first place? I understand that once you have your wallet, you will also gain access to your public key and private key... But in order to have a wallet ...
1
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0answers
16 views

Why, in general, are proofs of possession (POPs) “clearly” not sufficient for substantiating the knowledge of secret key (KOSK) assumption?

In Ristenpart, Yilek - The Power of Proofs-of-Possession: Securing Multiparty Signatures against Rogue-Key Attacks they have the statement: In general, such proofs of possession (POPs) are clearly ...
1
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1answer
81 views

How many required known plaintexts for an attack are considered insecure?

I stumbled over this problem when looking at symmetrical block ciphers with a relatively small block size like 32 bit. When I was looking at more common block ciphers with a 64 bit, I learned that ...
0
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0answers
26 views

How to encrypt a small number of identities (which are related to each other)? / Which algorithm has the smallest bit-length?

I'm looking for an encryption with as small numbers as possible. Given a small group of identities ($G$) (e.g. numbers from $1$ to $N$). Given one entry (or a small number) $e_i$ allows to compute ...
1
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1answer
88 views

CVP over $Z_{q}$ - is the problem still hard?

I'm reading about the CVP problem, and all the papers I've read so far handle the case where the CVP matrix and vector are over $R^{n}$ (or over $Z^{n}$), and the distance is a real number. However, ...
-1
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0answers
49 views

Are there any specific weaknesses in this crypto implementation?

I am reverse engineering the firmware of a particular router/modem. I am focusing on the functionality to export the router configuration. I an searching for a way to decrypt the configuration backup ...
1
vote
1answer
32 views

Are there any signature algorithms with pseudorandom signatures?

As the title says. My reference point for the "pseudorandom ciphertext" concept is this paper by Möller, which introduces a public-key encryption algorithm with this property. I want to know the ...
-1
votes
2answers
74 views

How to sell a piece of data through blockchain?

User A attempts to sell a piece of data D (byte level) to user B at price C through the blockchain. A and B do not trust each other. A worry: After the data D is delivered, B does not complete the ...
3
votes
1answer
126 views

Are “non-mathematical” encryption algorithms comparably secure against brute force key recovery?

I recently learned about a desktop encryption application called ALKEMI, which does not use mathematical encryption according to the website, which I understand to be a misnomer, at best: The ...
7
votes
2answers
2k views

Does a hash function have a Upper bound on input length?

I came across this Answer stating (just a line from the answer):- The input space is "infinite" and thus it has an infinite amount of values that will collide into a single hash And in the ...
1
vote
1answer
44 views

Securely rekey/re-encrypt AES-encrypted file

Suppose I have a big file encrypted using AES (any mode you want) with key kA. I'd like to give an untrusted proxy a kA->kB "conversion key" so that it re-encodes ...
1
vote
1answer
45 views

Do q-ary lattices have parallelogram kind of structure?

An $m$-dimensional lattice is defined by a basis $A \in \mathbb{R}^{m \times n}$ is the set of points $\{Az : z \in \mathbb{Z}^n\}$. A picture of these points would be like a nice parallelogram kind ...
-1
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0answers
25 views

Data Integrity check on IoT systems [on hold]

Sending a signed file from Onsite datacenter to IoT(box) or Linux box using any HSM Linux box will have a signed public key to verify the integrity. We should be able to generate the key pair on any ...
0
votes
1answer
46 views

How to calculate M when the attacker know e and w

Alice has a pair of RSA keys, the public key is $(n,e)$, the clear text message $M$ and the ciphertext $C=M^e \pmod n$. We suppose that Bob wants to encrypt two successive messages and send them to ...
0
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0answers
28 views

Fully homomorphic encryption - modulus switching technique [on hold]

How to implement modulus switching technique to reduce noise in fully homomorphic encryption scheme?
1
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0answers
8 views

NIST Randomess Test Running [migrated]

I am trying to run NIST randomness testing on an Input file having 3645018 bits. I can see that it's giving correct frequencies of Zero's and One's but I am not able to get the results of other test. ...
0
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0answers
20 views

Question about publication “Efficient (k,n) Threshold Secret Sharing Schemes Secure Against Cheating from n − 1 Cheaters”

In the paper on section "4 Proposed Scheme", I suppose that the scheme does not protect if an adversary has access to the $k - 1$ original shares, am I correct? If the adversary has $k - 1$ of both ...
0
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1answer
31 views

Whether ramp secret sharing possess additive homomorphism?

Ramp secret sharing replaces the random coefficients in original Shamir secret sharing with original data to be shared. In such a case, all the coefficients in the polynomial evaluation will be ...
-1
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0answers
28 views

Public Key VS Wallet Address - What is the difference? [migrated]

I am seeing a lot of contradictory information on why we now use Wallet Addresses rather than Public Keys. Some say that due to additional level of hashing (double hashing), Wallet addresses are ...
4
votes
4answers
71 views

Does larger key size mean larger data size in asymmetric encryption?

I'm new to cryptography. I know the larger the key size (like 128-bit vs 1024-bit) the harder the ciphertext is to crack, generally. But assuming everything else being equal, does a larger key size ...
0
votes
1answer
42 views

Asymmetric Encryption - How is the Public Key Being Shared?

I've been reading up on the relationship between private keys and public keys (as well as hashing), and I watched a few videos, but I am still a bit confused. I don't have a programming background, ...
0
votes
0answers
29 views

How to accept USDT payments the right way? [migrated]

We are developing an e-commerce solution and consider USDT to accept payments. At the moment as I understand we can generate many addresses (1 per transaction) with BIP32 spec approach. Based on Omni ...
-1
votes
0answers
38 views

pseudorandom permutation [on hold]

Assume that $F:\{0,1\}^{\lambda}\times \{0,1\}^{\lambda}\longrightarrow \{0,1\}^{\lambda}$ is a pseudorandom permutation. How to prove give two different pair $(k_{1},m_{1})$ and $(k_{2},m_{2})$, the ...
-2
votes
0answers
28 views

I was to send signed file to IoT system. How do I use PKI for this [on hold]

I was to send the signed file to the IoT system. How do I use PKI for this? I require to store a private key in HSM.
1
vote
1answer
42 views

Security of ciphersuite and key

Is anyone able to cite resources that can be based on choosing a cipher suite? In my case, for a VPN server (OpenVPN) I chose a set of ciphers: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 It provides 128 ...
0
votes
0answers
25 views

Generating Public Key For ECDH with Botan (C++) [closed]

I am trying to implement ECDH with Botan by using C++. First, I generated two private keys. Yet, I could not handle to make it for public keys. Botan::AutoSeeded_RNG rng; // ec domain and Botan::...
5
votes
1answer
148 views

Difference between Pure EdDSA (ed25519) and HashEdDSA (ed25519ph)

My question refers to EdDSA as specified in RFC 8032. I get from the RFC that ed25519 and ed25519ph are two different instances of EdDSA mainly differing in the fact that that in the case of ...
-4
votes
0answers
44 views

AES-256 Encryption 111 [closed]

In the Guarda cryptograph, the password was lost. There is a backup file backup.txt in which the keys are encrypted via AES-256. How to decipher?
-2
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0answers
34 views

Password cracking [closed]

Is there a program that automatically inserts the password options in the login field (as long as it selects the right one) using the search method and with the condition of approximate password data ...
1
vote
1answer
34 views

Nomenclature of Certificate Authorities and Certificates in PKI

In PKI there are different terms to identify certificate authorities in the chains. All terms I know of are as follow: Root Subordinate Super Intermediate I see all terms used interchangeably in the ...
0
votes
0answers
23 views

How to handle multiple key-agreements

If I would use two different key-agreements e.g. SIDH and ECDH how would I handle these both derived keys? Is there a different between XOR or SHA-256 the two keys? (Would one reduce the level of ...
6
votes
4answers
2k views

Can error correction and detection be done without adding extra bits?

I have gone through error detection and correction techniques like Hamming codes, and BCH codes require extra parity bits for detection and correction. While sending data, we always seem to introduce ...
1
vote
1answer
74 views

Difference between hash functions and algorithms?

Wikipedia lists "Hash function algorithms" within the "Hash function" page. I'm wondering what are the differences and if I can use the terms "hash(ing?) algorithm" and "hash function" interchangeably....
0
votes
0answers
19 views

Sign file (Client-Server) PKI-CA

I have a use case, the IoT system sending a signed file to the Datacenter and I have an internal CA to read the corresponding public key to verify the signature on the signed file. I am not sure how ...
2
votes
0answers
24 views

Is there a scheme to force a party to generate a fresh key?

Is there a way to force one party to generate a fresh key, such that another party can be convinced that the key was freshly generated, without that party also knowing the key? I'm motivated by a ...

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