# All Questions

4k 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 ...
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### 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, ...
203 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 ...
260 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. ...
3k 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 ...
297 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 ...
444 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 ...
185 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 ...
119 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 ...
120 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?
338 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 ...
1k 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 ...
155 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 ...
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### 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 ?
463 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: ...
214 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 ...
502 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 $d$ ...
176 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?
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### 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 ...
191 views

### EC Public Key length in ASN.1 DER

I have two X.509 certificates in DER format. A: ...
360 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 ...
326 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 ...
103 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 ...
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### 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 ...
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### 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 ...
286 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 ...
755 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 ...
438 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 ...
345 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 ...
70 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 ...
160 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 ...
57 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, ...
110 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 ...
197 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 ...
3k 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 ...
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### 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 ...
115 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 ...
883 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?
1k 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 ...
78 views

### Hash function and indifferentiability [closed]

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

### See any problems with this search-specific homomorphic encoding strategy?

I'm imagining this for use in the scenario of cloud-stored client-encrypted email, where, when seeking to do a string search across messages, you don't want to have to download every stored message in ...
88 views

### Keccak and compression functions

Keccak follows a sponge construction. Can we say that Keccak employs a compression function? Generally speaking, for sponge constructions, can we say that there is an underlying compression function? ...
127 views

### Determining average number of hash calls to get a hash that begins with X

I have been attempting to find an answer to a self-study question: If I have a hash algorithm that outputs 256 binary bits, on average, how many times would I have to call the hash function so ...
182 views

### Roots of polynomial in Shamir secret sharing

I need to know whether one can obtain any roots of the polynomial in Shamir secret sharing if he possesses less than threshold shares. For instance in (t,n) if he has t-1 shares can he obtain any ...
91 views

### stream cipher computation cost [closed]

With AES-CTR the computation time to encrypt a message of lengh $n$ blocks is $n$ computations of the block cipher. What is the running time to encrypt a message of $n$ bits using a stream cipher, ...
49 views

### Group Dependent Language

The text below has been taken from the below paper Groth-Sahai Paper. The relevant part is highlighted in red. What does this group-dependent language mean in this context? From the definition of a ...
288 views

### Strategy to crack a presumed substitution cipher

The ciphertext given is: ejitp spawa qleji taiul rtwll rflrl laoat wsqqj atgac kthls iraoa twlpl qjatw jufrh lhuts qataq itats aittk stqfj cae I've done ...