0
votes
0answers
17 views

Usage of different size chunks during AES encryption/decryption

I want to encrypt user's files on our server. For this purpose I decided to use php Mcrypt library. I choose Rijandel-128 algorithm and CBC mode for encryption. Since files are quite large I decided ...
0
votes
0answers
15 views

Creating passwords that are both secure and memorable

I have seven critical passwords. I want them to be long enough to be secure, memorable enough that I never forget them, unique enough to resist an attacker. How do I achieve this?
0
votes
0answers
14 views

Recommendation for authenticated ephemeral key exchange

I am working on a home project and I wanted to implement an authenticated ephemeral key exchange using Elliptic curves. I first thought about Station-to-Station with EC protocol, but it does not seem ...
0
votes
0answers
24 views

Cryptography Implementation in software

I am trying to implement a password manager in C and I had a question about the proper steps in implementing the crypto. I looked at some implementations, google talks on crypto and what the standards ...
1
vote
1answer
28 views

Is a tweakable block cipher still considered deterministic in nature?

"a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called blocks, with an unvarying transformation that is specified by a symmetric key. - Wikipedia " But with a ...
1
vote
2answers
94 views

Diffusion in Shamir's secret sharing scheme

The popular command line utility ssss implements the classic Shamir's secret sharing scheme over the generic field $GF(2^q)$ with $8 \le q \le 1024$. When $q>=64$, the constant coefficient ($c_0$) ...
0
votes
0answers
51 views

XORing a header with SHA512-hash - secure?

I am writing a application that encrypts text several times and stores the result. The result looks like complete random bytes, therefore I add some random bytes at the end. To let the program know ...
-1
votes
0answers
41 views

Hybrid encryption with Textbook RSA [on hold]

A common variant of textbook RSA is the following: During key generation, the modulus $N$ is chosen as usual. We chose $e$ as $e:=3$ (instead of random). Then $d$ is chosen with $e\cdot ...
1
vote
1answer
40 views

MAC security and adversaries with memory

The usual definition of MAC security is (roughly) that there is no "efficient" adversary that has non-negligible advantage in the "MAC game" where the MAC game is as follows: the challenger chooses a ...
2
votes
1answer
81 views

Is there a reason that the N value in scrypt is limited to powers of two?

I have been looking at the scrypt hashing algorithm and am confused as to why the N value, which determines the overall cost, is limited to powers of two. There are ...
3
votes
1answer
54 views

Security of KDF1 and KDF2 (hash based KDF's)

It's still common to come across implementations of KDF1 and KDF2. Basically these are KDF's that simply derive multiple keys from the key seed and a counter: $K_i = KDF(K_{master}, i) = H(K_{master} ...
1
vote
0answers
48 views

Cryptographic library quality [on hold]

I've been working on a project that will require secure communication over the internet, so I've been thinking of TLS 1.2. After looking around I chose Botan but then I thought about using a more ...
1
vote
2answers
57 views

How to calculate Modulo using a standard calculator for a one time pad encryption

I wrote a simple python script to preform one time pad encryption I would like to be able to decrypt the ciphertext by hand. In my script I use mod 26. This is how I was shown to calculate a mod ...
1
vote
1answer
103 views

What does it mean when two encrypted files, encrypted with the same method but with different keys, when xor'd together, produce a repeating pattern?

Let's say I have fileA and fileB, both encrypted somehow, but in the same method with different keys. If I xor them together, they will make a repeating pattern of 32 bytes length. What does that ...
0
votes
0answers
40 views

ECDSA verification is too slow [on hold]

I found that ECDSA is too slow while verifying signatures; can you tell me why? I'm planing to speed it up, so what tips should I consider to make it fast?
3
votes
2answers
143 views

How vulnerable is the C rand() in public cryptography protocols?

I just learned about the basics of public cryptography a few weeks ago and I am curious as to why the C rand() function should not be used for crypto schemes. For example, say I want to generate a ...
0
votes
0answers
30 views

RSA algorithm , decrypting a message [on hold]

I have to decrypt a message (24-264-291-291-220) using RSA algorithm given the private key. I did all the calculations and the decryption of that message is 74-66-48-48-55. My question is how would I ...
0
votes
0answers
16 views

Client-server authentication protocol suggestion [migrated]

I'm designing an authentication methods for my client/server system consisting of: a windows desktop client application (.NET) windows/linux servers (C++) one "security server" which authorizes the ...
-1
votes
1answer
70 views

Constants Differ in SHA1 implementation

https://code.google.com/p/crypto-js/source/browse/tags/3.1.2/src/sha1.js ...
-2
votes
0answers
50 views

RSA and ECDSA algorithms [on hold]

Hi, i want to learn more about ECDSA and RSA Digital signatures , could you give me both Algorithms for sign and verify the data.
0
votes
2answers
138 views

Decrypting a small Message using RSA with a Private Key [on hold]

If I have a private key of (43, 341), what would be the steps I need to take to decrypt a small message using RSA. I have looked ...
1
vote
1answer
105 views

One time pad: why is it useless in practice?

The symmetric cryptosystem One time pad (OTP) seems to be very beautiful since it is perfectly secret according to Shannon. Many books, however, point out that the main drawback is that one must ...
-2
votes
0answers
43 views

mathematical derivation for elliptic curve cryptography [on hold]

how to derive the mathematical derivation for elliptic curve cryptography,please to send full detail derivation for elliptic curve cryptography,and also i need how to use the galois field in ...
0
votes
0answers
31 views

Is it possible to forge elgamal in a determinsic way? [on hold]

El Gamal is existentially forgeable, would it be possible to forge it in a deterministic way ,i.e., eliminating the randomness? Maybe by using fermats little theorem ?
0
votes
1answer
73 views

Using Stream Cipher as CSPRNG

Are there any guidelines or justification for converting a stream cipher algorithm for use as a CSPRNG? For instance, lets say I wanted to convert one of the eStream portfolio Profile 1 (software) ...
1
vote
1answer
53 views

Do Chosen-Chiphertext attacks only apply to public-key cryptosystems?

Do Chosen-Chiphertext attacks (CCA-1/2) only apply to public-key Cryptosystem?
0
votes
1answer
90 views

Is ElGamal still unforgable if the adversary knows r

Is ElGamal still unforgable if the adversary knows the value of $r$ that was calculated by $g^k$? When we do sign the message $msg$, we calculate $r = g^k$. As we know the regular ElGamal ...
1
vote
1answer
82 views

The relationship between the key length and encrypt time in Xor algorithm?

I did work on the encryption algorithm and the decryption using the XOR method noticed that when more the key length, the less time spent on encryption and decryption. I have two questions in ...
0
votes
0answers
70 views

Is it possible to crack any MD5 hash? [on hold]

I really wonder is it possible to crack any MD5 hash?
2
votes
1answer
53 views

Security of permutation cipher

I would like to understand how secure the permutation cipher is. I would specifically like to understand the following concrete setup: If the alphabet is $L = \{0,1,\dots , 255\}$ and $\sigma_1, ...
3
votes
1answer
68 views

Is the strength of RSA over quadratic or other cyclotomic fields as strong as over the integers?

If we assume the strength of RSA is based on the difficulty of factoring (which I know we can't guarantee) and we compose the modulus of some other quadratic ring that is a unique factorization domain ...
0
votes
1answer
89 views

ECDSA Public Key generation

Referring to both Wikipedia page and ECDSA-cert paper I can understand that, given $\mathcal{E} = \mathcal{E}(a,\,b,\,\mathbb{F}_{2^m})$ as our elliptic curve on $\mathbb{F}_{2^m}$ group $G \in ...
1
vote
0answers
33 views

Would usage of jCryption 3.0 + SSL have mitigated the Heartbleed vulnerability? [migrated]

I came across a project called jCryption 3.0, which encrypts data between the client and server, without using SSL. If a website's JavaScript had used jCryption 3.0 to encrypt login form fields before ...
0
votes
1answer
53 views

Composing hashes and/or MACs

Suppose I have n hash/MAC functions, of which n-1 are extremely insecure, leaving only one that is in fact cryptographically secure. If I use all of them on a message and the XOR them together the ...
0
votes
0answers
27 views

Is anyone aware of Du atallah multiplicative secret sharing scheme for dot products for > 2 party scenario?

I am working on Du Atallah's multiplicative secret sharing scheme for more than 2 party scenario. Is anyone aware of its multiparty version (more than 2 parties). The paper for 2 party can be found ...
-1
votes
0answers
40 views

Which commitment scheme is better for malicious models [on hold]

Can some one suggest which scheme is better for malicious models in terms of efficiency and security? A Pedersen's VSS based scheme or the one based on Fiat-Feige-Shamir digital signatures ?
0
votes
1answer
81 views

Existence of a map $\phi:\mathbb{Z}_{N^2}^* \mapsto \mathbb{F} $

Is there a map between the group of $\mathbb{Z}_{N^2}^*$ where $N$ is a composite number , a product of two equal size secure prime numbers $p$ and $q$ and a finite field $\mathbb{F}$, such that for ...
0
votes
0answers
85 views

SSL-like protocol with public-key hard-coded in the client

Imagine a SSL-like protocol that instead of using certificates signed by a trusted CA, has the server's public key hard-coded in the client. My question is: what happens if the server's private key is ...
-1
votes
1answer
184 views

How can I convert numbers into prime numbers?

I'm working with one-way accumulators, but I'm not knowledgable in cryptography. Is there an easy peasy way to hash numbers (or whatever) into prime numbers? Obviously I'd like it to be collision ...
1
vote
0answers
32 views

What happens if biometric data is stolen? [migrated]

This question isn't very specific, but I think it would be ok to post it in the cryptography StackExchange (hopefully). As we move toward a future where fingerprints might possibly replace passwords, ...
0
votes
0answers
20 views

Decrypt Passwords based on using a user's password [migrated]

I am creating a database to store our client's information at work (a heritage center specializing in DNA based genealogy. Once the results of a test come back we have people that use the information ...
3
votes
1answer
62 views

Has there ever been more then a theortetical difference between preimage resistance and second preimage resistance?

In other words, has there ever been a point in time in which having the content of a message has actually helped break a hash function?
5
votes
1answer
117 views

Block cipher and parity of permutation

Can anyone explain the following text passage to me? Most real-world block ciphers build even permutations, because it's hard to build odd ones using small operations (32 bit) on larger (128 ...
0
votes
0answers
65 views

Could program verification techniques prevent bugs of the genre of Heartbleed from occurring? [migrated]

On the matter of the Heartbleed bug, Bruce Schneier wrote in his Crypto-Gram of 15th April: '"Catastrophic" is the right word. On the scale of 1 to 10, this is an 11.' I read several years ago that a ...
1
vote
0answers
49 views

SHA256 Padding and Parsing [closed]

Can anyone please help me with basic Verilog Structure for Padding and Parsing stages of SHA256. I have Googled it a lot but couldn't find it. I'm stuck at How to check the Size " L " of the random ...
-1
votes
1answer
45 views

Positioning of keys in encrypted text

I'm just looking at very simple encryption. I've noticed that the key is typically either at the front or at the back of the encrypted text. This is quite easy to break if you know the key. It can ...
1
vote
1answer
40 views

What is a 'secret key factory'? What precisely is it doing? [closed]

I have found a Java implementation of AES CBC mode that runs in Netbeans. The lines below appear to create the key from password and salt: ...
0
votes
1answer
22 views

Does IKEv2 protocol have two modes like IKE

IKE Protocol have 2 modes, that modes have different structure. Does IKEv2 protocol have two modes like IKE.
3
votes
2answers
168 views

Are there any elliptic curve asymmetric encryption algorithms?

RSA offers the functionality of encrypting (short messages, or symmetric keys) with a public key, and decrypting with a private key. However, RSA key generation is extremely expensive, especially for ...
0
votes
0answers
5 views

Certificate Revocation List [migrated]

There are many fields on a certificate revocation list (CRL) like Algorithm, Parameters, Issuer Name, This update date, Next update date, user certificate serial #, etc. While I understand the purpose ...

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