1
vote
1answer
103 views

How can I do minus on plaintexts in the Paillier cryptosystem?

We have $E(a)$, $E(b)$ encrypted under the same Paillier key. As we all know, we can get $E(a+b)$ by calculating $E(a)*E(b)$. But can we get $E(a-b)$, by calculating $E(a)/E(b)$? I tried to ...
2
votes
3answers
305 views

Alternative to NSA encryption algorithm

I am looking for a strong alternative to elliptic curve cryptography. It should be something that could face quantum computing attacks, but nothing created by the NSA. I heard about isogeny key ...
6
votes
1answer
315 views

Single-purpose symmetric encryption scheme for single files

I'm writing a simple password manager program that will encrypt/decrypt a single file (it's size will most likely stay under a few K). This is my initial file format design: ...
1
vote
1answer
104 views

Question about second preimage resistance of hash function combiner

Let $\Pi=(Gen_1,H_1)$ and $\Pi=(Gen_2,H_2)$ be two hash functions. Define $(Gen, H)$ so that $Gen$ runs $Gen_1$ and $Gen_2$ obtaining $s_1$ and $s_2$ respectively. Then let ...
0
votes
1answer
180 views

Generating child keys for a hill climb algorithm

As a little pet project I'm writing some code to do a little cryptanalysis. Starting with something simple I have created a hill climbing algorithm for solving a simple substitution cipher. So I ...
1
vote
1answer
121 views

Correctness vs Completeness

What is the conceptual difference between the definition of correctness and completeness in verifiable cryptographic protocols? They justify that if a statement is correct then the verification should ...
1
vote
0answers
45 views

Need to choose an ecnryption method [closed]

I've got an homework to implement an encryption algorithm (I can choose what), now we didn't learn about encryptions yet, I guess you can call it pre-class homework or something, I know what is ...
5
votes
1answer
2k views

How to choose between AES-CCM and AES-GCM for storage volume encryption

We are using the encryption built into Solaris 11 ZFS, which offers the choice between CCM (CBC counter mode) and GCM (Galois counter mode). What are the pros and cons of choosing each of these cipher ...
-1
votes
1answer
67 views

What is the translation for “hash” in french? [closed]

I am doing a French presentation on basic cryptography, and the generation of random numbers. Most terms are easily translatable, but I can't seem to find a word for hash, as in cryptographic hashing, ...
7
votes
4answers
187 views

Is deniable error-correction possible?

This question came up as I tried to answer an earlier question I asked: cryptographic data structure wanted: sparse array without membership test. I still have not resolved that question to my ...
2
votes
1answer
204 views

Small Encryption Exponent

I am trying to crack an unpadded RSA set up for a homework. I have public key (R,e) and encrypted message E. ...
6
votes
2answers
2k views

Strength of MD5 in finding duplicate files

Why are there a lot of duplicate file finder applications which are using MD5 Algorithm? What is the strength of MD5 in terms of searching duplicate files in hard disk or flash driver or any other ...
0
votes
1answer
158 views

How does Blowfish avoid successful cryptanalysis? [closed]

I have researched the Blowfish algorithm and am curious as to why there exists no effective cryptanalysis for this algorithm as of yet. What basic principles or features allow Blowfish to achieve ...
2
votes
3answers
248 views

Any weakness when sha256'ing output of sha256, repeatedly?

Is it significantly easier to reverse a sha256 hash if you know that the input was a 32 byte output of sha256? I assume for most outputs of sha256 there will be zero, one or two possible 32 byte ...
1
vote
1answer
120 views

Triple DES in Firefox - in practice

Reading about triple DES and understanding the principles, I am still curious how Firefox defines their three keys for the encryption/decryption. Suppose that the user saves his passwords in the ...
0
votes
1answer
98 views

Known-plaintext attack on two-dimensional affine cipher

Problem: We have a two-dimensional affine cipher with $n = 2,\,\,\,\mathcal{P} = \mathcal{C} = {\mathbb{F}_{16}^2}$, where $\mathcal{K} = \{ A,\,\,b\} $ and $b = (0,0)$. The encryption and decryption ...
-3
votes
2answers
1k views

finding collision for truncated SHA1 hash output

Suppose we truncate only 40 bits of sha1 hash output.hence it is insecure.how can we find two message as input which gives first 40 bits of hash as same value i.e we have to find collision for first ...
-1
votes
1answer
67 views

Witness and Commitment in Commitment schemes [closed]

In connection to a commitment scheme, how are witness and commitment different? Are 'Binding' and 'Hiding' properties defined w.r.t. witness and commitment or both?
1
vote
3answers
308 views

What is h in this RSA variant?

I am trying to implement a proposed improved algorithm of RSA . Here the author has increased the number of exponents. However I am unable to understand what $h$ is in the Key generation step. Can ...
-1
votes
2answers
731 views

Open source implementations of Symmetric Searchable Encryption and Order Preserving Encryption [closed]

Are there open source implementations of SSE and OPE? Can anyone please point to sample codes, if available. EDIT If cryptDB is not an option, what other options are available? (Indeed, these ...
0
votes
1answer
113 views

A variant of Shamir secret sharing

Suppose implement the Shamir secret sharing as following: we select a degree $d$ polynomial $P$ with a zero coefficient of 0, and all other coefficents selected randomly from $Z_p$; and to this ...
1
vote
1answer
49 views

Hardness proof?

I am little curious about how do we calculate hardness proof of any cryptography algorithm? Also where can I find hardness proof for AES and AES-CBC ?
2
votes
1answer
150 views

what are DP and DQ in Encryption by RSA in c#

I want to know about these tags in RSA Encryption by private Key. when I use this code: ...
3
votes
3answers
161 views

Why are we not using multiple ciphers per message?

I am aware of at least rsa, elgamal-encryption, and variations of elliptic-curves relying on different problems and that those problems are considered hard. However, if someone figures out a way to ...
2
votes
1answer
205 views

Calculate the RSA private exponent from the CRT parameters

I am trying to make the RSA structure of Openssl manually, knowing the public key ($n$, $e$) and the CRT parameters $p$, $q$, $d_P$, $d_Q$, and $u = q^{-1} \mod p$. That is, I want to get the $d$ ...
4
votes
1answer
139 views

Is SRP post-quantum secure?

Is SRP-6a post-quantum secure? If it is not post-quantum secure, do any post-quantum secure alternatives similar to SRP-6a exist?
0
votes
0answers
39 views

Is Attribute based encryption sub-class of Identity based encryption [duplicate]

I have a basic question related to Identity and Attribute based encryption. Construction of IBE scheme was first shown by Boneh et al. in 2001 and I think in 2004 Sahai and Waters introduced ...
1
vote
1answer
92 views

EC Public Key length in ASN.1 DER

I have two X.509 certificates in DER format. A: ...
4
votes
2answers
236 views

CDH problem and Square-DH problem

CDH problem roughly says that choose $U=g^u, V=g^v$ uniformly at random from cyclic group $G$, it's hard to compute $CDH(U,V)=g^{uv}$. Square-DH problem roughly says choose $U=g^u$ uniformly at ...
1
vote
2answers
175 views

Strength and weaknesses of this JavaScript charCodeAt based login script

I know of a company on their website who are using this very basic password login page written in JavaScript. This doesn't seem very secure at all, because in the html source code it shows where the ...
-1
votes
1answer
89 views

Is One Time Pad something like this? [closed]

Alphabet: [A-Z] = [0-25] Plaintext = HELLO = 7 4 11 11 14 // QUESTION: do this key must be as long as plaintext? KEY: [QWERT] KEY = 16 23 4 17 19 Plaintext + Key = 23 27 15 28 33 Plaintext + Key ...
2
votes
1answer
281 views

Hierarchical Encryption

Is there a way to setup a hierarchical encryption using public key encryption? Let's say a higher level user can decrypt messages encrypted by lower level users. Is that possible? I guess it is only ...
13
votes
1answer
4k views

Compare Blockmode CBC (with diffuser) against XTS

I have some problems in understanding the "advantage" of AES-XTS compared to CBC with diffuser. I read something about FileVault, in this paper they mention the two modes of operations XTS and CBC ...
4
votes
1answer
259 views

reducing false positives in searchable encryption

Practical techniques for searchable encryption proposed by Song et al. [1] have a false positive rate of $l/2^m$ where $l$ is left half of encrypted bits and $m$ is right half and $l+m=n$ where $n$ is ...
7
votes
1answer
701 views

Why should CAST5 and 3DES not be used for encrypting files over 4GB?

On https://www.gnupg.org/faq/gnupg-faq.html#define_cast, it says that Like 3DES, its 64-bit block size means it should not be used to encrypt files larger than 4Gb in size… How and why does the ...
0
votes
0answers
150 views

Possible Digital Signature Hack?

I am starting to learn more about cryptography and I just read more about how asymmetric keys can make a digital certificate, and I would like if someone could explain me why the following case can't ...
1
vote
1answer
166 views

Message encrypted with a LFSR based stream cipher

I am learning about LFSR sequence and I came across this question: A 16-bit message consists of two ASCII characters. This message was encrypted with a one-time pad, and the key for the one-time pad ...
2
votes
0answers
53 views

Bridging the gap between security proofs and “real-world” security

I've been studying cryptography for a little while. I understand fairly well the nuts and bolts of security proofs, but I'm having trouble reconciling the formal statements of security in these proofs ...
1
vote
1answer
104 views

INT_32_BE in PBKDF2

Trying to understand PBKDF2 in detail. It is clear that the password and the salt is given to the PRF (which is HMAC-SHA-1 in the specification). But what is the role of the INT_32_BE(i)? What does it ...
3
votes
3answers
435 views

Is there any area where AES-CBC cannot be used ? If so, why ?

I would like to know the domains or specific applications where using AES-CBC is not advised due to any drawbacks like sequential encryption of AES-CBC ?
1
vote
0answers
53 views

Are there any obvious techncial faults in F. Ruiz's 2013 URSA javascript cryptography? [closed]

The link to the cryptography is here: http://prgomez.com/ursa/ I have found the following simple javascript system of encryption/decryption portable and easy to use for emails and messaging sites, ...
2
votes
0answers
106 views

Cipher built from GPU primitives [closed]

Is it feasible to build a cipher (or hash) out of GPU or DSP primitives (e.g. big matrix multiplication, Fast Fourier Transform, big block SIMD, or hardware H.264/AVC codec)? Preferably those are slow ...
0
votes
2answers
125 views

Does brute force attack use the program that created the ciphertext?

I've read several articles about brute force cryptanalytic attacks, but none explicitly say what algorithm is being run for each attempt, nor what criteria is used to declare an attempt a success or a ...
6
votes
2answers
2k views

Encrypting and obscuring data between site/user without SSL

Im trying to figure out what the best way to encrypt data sent between a webpage and the user(both ways) is, when hosted in an environment that doesn't support SSL. The purpose of encryption would be ...
3
votes
1answer
55 views

NIZK Proof of knowledge N of M discrete logarithms (threshold)

It is well known how to produce a NIZK that curvepoints $aG$ and $aP$ have the same discrete logarithm $a$ with respect to the curvepoints they are multiplied by. There is also a way to prove that a ...
0
votes
2answers
84 views

Brute Force Attack Strategies

A Brute Force Attack obviously involves attempting to decrypt ciphertext (with the associated plaintext being known) using all possible encryption keys. Aside from attempting all possible ...
6
votes
3answers
824 views

Is there benefit to signing unencrypted emails?

I came to this article from another comment on Crypto StackExchange. After reading it, I am wondering if there is any benefit to using a digital signature on unencrypted S/MIME emails?
-1
votes
2answers
507 views

Vigenere ciphertext encrypted with another vigenere cipher

I have been learning about Vigenere ciphers and then thought of this scenario: if a cryptographer encrypts a plaintext English message with a Vigenere cipher and then another cryptographer, who wants ...
0
votes
1answer
53 views

Hash function and indifferentiability [closed]

What are the properties derived from the fact that a hash function is indifferentiable from a random oracle?

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